Printer Friendly

Meta-Analysis of the Relationship between Deep Brain Stimulation in Patients with Parkinson's Disease and Performance in Evaluation Tests for Executive Brain Functions.

1. Introduction

Parkinson's disease (PD) is a common, progressive and incurable neurodegenerative disease with an unknown etiology, whose main symptoms include motor alterations such as shaking, an abnormal increase in muscle tone, bradykinesia, postural instability, impaired balance and walking, and emotional inexpressiveness [1-6]. In postmortem studies of patients with PD, these clinical features have been directly related to the reduction of dopamine neurons in the cortical-thalamus-striated loop [1, 4-7], mitochondrial alterations [4], and the presence of clusters of [alpha]-synuclein presynaptic protein, known as Lewy bodies [4,7, 8].

From a neurological perspective, the symptoms of PD have been considered to be the result of alterations in the communication between the direct/indirect motor control pathways of the basal ganglia. According to this "classic" model, this deficiency in communication is given by a reduction in the dopaminergic transmission which in turn results in the diminished inhibition of the indirect pathway, the excitation of the direct pathway, and the excessive activation in the discharge of internal globus pallidus (GPi) and an inhibition of the thalamic cortical motor system [9, 10]. Given the model's limitations in explaining PD systems other than the motor ones, it is recognized that the Cortico-Basal Ganglia-Thalamus loop is implied in eye movement control functions (the oculomotor circuit) [11], memory and spatial orientation (dorsolateral prefrontal circuit) [10], behavioral adjustment and control, and the reward and punishment system (lateral orbitofrontal circuit) [9].

It has been suggested that cognitive [9], emotional [12], and behavioral [13] alterations can be generated in the BG-cortex communication. In this same sense, although it has not been a characteristic present in all the reports, a significant metabolic reduction has been found in patients with Parkinson's disease, predominantly in areas of parietal and medial frontal association [5].

Among the nonmotor clinical symptoms there is a broad spectrum of alterations at cognitive [1, 9, 14], emotional, mood [15], behavioral [16, 17], and psychiatric levels [17, 18]. In some cases, the cognitive deficit is comparable to executive alterations similar to patients with lesions in the frontal lobe, given the reduction of dopaminergic activity in the frontostriatal circuits, but without being considered a "frontal lobe syndrome," leading to episodic alterations and visuospatial and verbal fluency dysfunctions [9,19]. Previous studies have reported on the appearance of alterations in tasks that assess executive brain functions, such as verbal fluency [20], Trail Making Test (TMT-B), Wisconsin Card Sorting Test (WCST), Stroop [19], Theory of Mind [21,22], and timing deficits [23].

The treatments reported for PD include dopamine antagonist pharmacological treatments [2, 3, 24], physical therapy [25, 26], genetic therapy [24], transcranial magnetic stimulation [15, 27, 28], injury to the subthalamic nucleus [29], and high frequency deep brain stimulation (DBS) [30-37]. The latter has been proven to reduce the severity of motor symptoms, to reduce pharmacological treatment significantly, and to improve patients' quality of life [1, 31, 32, 35, 36, 38-40]. DBS has been reported in subcortical structures such as the subthalamic nucleus (STN), the internal globus pallidus (GPi), the pedunculopontine nucleus (PPN), and prelemniscal radiation [35, 36, 41-45]. Stimulator frequency depends on the patient's clinical aspects and the location of the electrodes [31, 42].

In the assessment of nonmotor symptoms (disturbed sleep patterns, salivation, mood, cognitive, and executive function), it has been reported that the DBS procedure fosters a number of changes. In DBS of the STN, Bickel et al. [29] found that general performance remained constant in frontal executive function tests [16, 23]. In bilateral DBS of the STN, significant improvement has been reported in the learning of verbal information and visuoconstructive skills when there is increased stimulator amplitude [38, 46]. Inasmuch as the DBS of the PPN, improvements have been reported in terms of tasks related to working memory (MT) [23,47]. It has also been reported that STN-DBS is involved in the generation of impulse control disorders but that this is not a maintained effect [48].

Some studies have identified metabolic changes associated with execution of tasks, reporting that there is an activity reduction network in PD that includes the supplementary motor area (preSMA), precuneus, the inferior parietal lobe, and the left prefrontal cortex, as well as an increase in the cerebellar vermis and the dentate nucleus, probably due to the cerebellum-BG connections [5, 49]. Changes in the structures of this area can be seen in tasks that involve cognitive performance which may suggest that alterations in the network play a role in other cognitive functions [50].

A central aspect of this study is the DBS procedure and its impact on nonmotor symptoms in PD [40]. Thus, a meta-analysis of 28 studies was carried out of studies by Parsons et al. [51]. The authors analyzed the cognitive consequences of STN-DBS, concluding that the procedure presents a small effect on all the cognitive domains assessed, except on verbal fluency, shedding light on a lower statistically significant performance in phonetic and semantic verbal fluency tests after DBS.

Given the lack of consensus inasmuch as the impact of the DBS procedure on executive brain functions specifically, the aim of this study was to identify changes in the executive brain functions tests after DBS in six months or more, reported in the last ten years. To do this, we used studies that showed results for before and after DBS and analyzed these using meta-analysis.

2. Method

2.1. Study Selection. An information search was carried out in the Scopus databases using the following key words: "deep AND brain AND stimulation AND Parkinson AND executive AND functions." The search yielded 126 articles that covered the 2005-2015 period. Using the same keywords, the Pubmed database yielded 39 results; the Web of Science (WOS) database, 104 results; the Sage journals database, 142 results; the Taylor Francis Online database, 125 results; the Wiley Online Library, 1362 results; the Embase database, 149 results; and Proquest, 3295 results. Finally, using the PsychNET database, the search initially gave no results; thus it was modified using the words "Parkinson AND DBS," yielding 6 results. This gave a total of 5348 records in 9 databases. The results were subsequently grouped by year and types of journal articles.

The cleaning process was undertaken in two phases. The first was a selection of articles published in science journals, excluding reviews, meta-analyses, and case studies. The results for this first phase are shown in Figure 1.

2.2. Study Inclusion Criteria. The studies were selected considering the following recommendations: (a) types of design; (b) types of intervention; (c) participant characteristics; (d) statistical data; and (e) the tests used [52]. All the reported studies were written in English and dated between 2005 and 2015. The inclusion criteria for this meta-analysis were the following: (a) pre- and postsurgery testing of stimulator implantation; (b) for the target, the subthalamic nucleus, globus pallidus, and other structures related to movement; (c) sociodemographic variables were not taken into account for participant characteristics (age, how long the patient has had the disease, educational level, and type of medication); (d) studies that reported means, standard deviations, t-tests, significance levels; and (e) only those studies that reported some kind of test that assessed executive brain functions (working memory, verbal fluency, cognitive flexibility, planning, inhibition, and abstract thinking) and processing speed. Figure 1 outlines the search procedure. Nonadditional studies were identified by contacting clinical experts and searching bibliographies in local repositories.

2.3. Codification of the Studies. The studies were codified independently by 4 researchers and the codified information was subsequently corroborated. The following characteristics were taken into account for the codification: (a) identification of the study by the first author's surname and the year of publication; (b) the number of participants; (c) the study design (before and after surgery; only after surgery; cases and controls; and correlational); (d) location of implanted deep brain stimulation (subthalamus; globus pallidus; and other); (e) parameter related to the stimulator (pulse, frequency, voltage, and electrode type); (f) schooling (secondary education, university education, graduate studies, none, and not reported); (g) age (under 50, 51-60, 61-70, over 70, and not reported); (h) time of suffering from PD symptoms before brain stimulation surgery (short, less than 5 years; medium, 6-10 years; late, more than 10 years; and not reported); (i) sex (men, women, mixed, and not reported); (j) socioeconomic status (reported, not reported); (k) type of medication; (l) results values associated with the executive brain functions tests undertaken (Table 1); and (m) time before assessment after the stimulator implantation surgery. When the information was codified for the meta-analysis, the time after stimulator implantation variable was not taken as a homogenization criterion for the studies. That is, for those that presented more than one posterior measurement, the measurement closest to 12 months after the surgery was used.

The executive brain functions considered in the study analysis include verbal fluency, cognitive flexibility, working memory, processing speed, behavioral inhibition, and planning (Table 2). Following Parsons et al. [51], the verbal fluency assessment tasks were separated due to the reported systematic reduction of the verbal fluency function in patients with PD with DBS and the difference (category or letters) in terms of task processing.

2.4. Statistical Analysis. The mean scores of the tests undertaken were calculated and Hedges's g values and standard error (SE) for each study are reported together with 95% confidence intervals (CIs). It was assumed that if value I2 was below 50% of heterogeneity, a meta-analysis with a fixed effects model would be applied; otherwise, a random effects model would be used [57].

To assess the publication bias, a funnel plot was used for each of the meta-analyses [58]. The meta-analysis and funnel plot were carried out using the Comprehensive Meta-analysis 2.0 software. p < 0.05 value was considered to have statistical significance.

3. Results

Once the search was refined, 5348 studies were analyzed (Figure 1). Figure 1 shows the results of the initial search.

3.1. Descriptive. The descriptive results are shown in Table 2 which outlines the studies, number of patients, age, time of illness, schooling, PD alteration scores, and other values reported for the studies.

3.2. Meta-Analysis. For this study, a fixed effects model was used due to two conditions. First, the conditions of the participants and characteristics of the disease are similar among the studies and with this a population effect size is theoretically assumed [52, 59]. On the other hand, given that it was previously assumed that the percentage of heterogeneity exceeded 50% measured by coefficient [I.sup.2], a random effects model was used [57]. It is important to signal that only one study has results of GPi stimulation (Rothlind, 2015) and because of this the results and figures were not separate.

3.3. Verbal Fluency. Figure 2 outlines the funnel plot of the SE for studies of verbal fluency and there is no bias in the studies reported [58]. In this category, we obtained 21 studies that were clustered depending on the evaluation modality (semantic or phonetic), Hedges's g was used to determine the size of the effect, obtaining a medium effect size (Hedges's g = -0.266; SE = 0.036; CI -0.337 to -0.195), which showed heterogeneity ([Q.sub.(20)] = 42,911; p = 0.002) within an average percentage ([I.sub.2] = 53,39%), which, when in excess of 50%, led to the application of a random model [60]. The results also showed a significant reduction in performance in the test after the DBS procedure (Z value = -5,607; p < 0.001) (Figure 3).

3.4. Cognitive Flexibility. This function was assessed based on the Wisconsin Shorting Card Test (WSCT) and Trail Making Test (TMT) in its B and B-A versions. Figure 4 shows the funnel plot used for the SE in WSCT; the figure shows three points outside the projection in the upper threshold, but these are shown as equivalents to the points on the lower threshold. The meta-analysis obtained 27 results in which the Wisconsin Shorting Card Test (WSCT) in its different versions (Nelson or Modified) was assessed, bearing in mind the different types of scores (errors, perseverations, or categories). A small effect size was found (Hedges's g = 0.064; SE = 0.053; CI -0.04 to 0.167), showing heterogeneity ([Q.sub.(26)] = 44,94; p = 0.012) within an average percentage ([I.sup.2] = 42,14%), but without exceeding 50% [43,60]. There seems to be no significant change in the test scores after the DBS procedure (Z value = 1,656; p = 0.098) (Figure 5).

Using the Trail Making Test (TMT-A), 6 results were obtained; Figure 6 shows the funnel plot for the SE of the test, and no biases are observed. The studies in the metaanalysis reveal no differences in terms of execution (Z value = -0.328; p = 0.743), the effect detected was small (Hedges's g = -0.02; SE = 0.061; CI -0.14 to 0.1), and the results showed homogeneity ([Q.sub.(5)] = 3,202; p = 0.669)withinthe 0% value([I.sup.2] = 0%) (Figure 7). With respect to the other tests for the same function such as version B of the TMT, 10 of the results found did not reveal an important change between the applications (Z value = 0.912; p = 0.362), the effect detected was small (Hedges's g = -0.02; SE = 0.053; CI -0.056 to 0.153), and the results showed homogeneity ([Q.sub.(9)] = 6,973; p = 0.64) at a very low percentage ([I.sup.2] = 0%) (Figure 9). Figure 8 presents the funnel plot for the SE of the TMT-B. Finally, for the TMT-B-A version (5 results) the funnel plot is presented in Figure 10 and no differences were found between applications before and after the DBS procedure (Z value = -0.404; p = 0.686). The effect detected was small (Hedges's g = -0.04; SE = 0.099; CI -0.234 to 0.154), and the results showed homogeneity ([Q.sub.(4)] = 2,251; p = 0.69) at a very low percentage ([I.sup.2] = 0%) (Figure 11).

3.5. Abstract Thinking. Figure 12 shows the funnel plot and no bias among the studies was observed. In this category, 6 studies were obtained, and no changes in test performance were observed after the DBS procedure (Z value = 0.722; p = 0.471) (Figure 13). A small effect size was obtained (Hedges's g = 0.058; SE = 0.080; CI -0.099 to 0.215), and the result showed homogeneity ([Q.sub.(5)] = 3,088; p = 0.686) within a low percentage ([I.sup.2] = 0%).

3.6. Working Memory. Figure 14 shows the funnel plot and no bias among the studies is observed. In this category, 22 results were obtained, and no changes in test performance were observed after the DBS procedure (Z value = -1,533; p = 0.125) (Figure 15). A small effect size was obtained (Hedges's g = -0.051; SE = 0.033; CI -0.115 to 0.014), and the result showed homogeneity ([Q.sub.(21)] = 13,682; p = 0.883) at a low percentage ([I.sup.2] = 0%).

3.7. Inhibition. Figure 16 shows the funnel plot for inhibition; a number of scores outside the lower and upper thresholds were obtained suggesting a bias in the studies. However, when visual criteria were applied, the bias does not present itself fully, and there are a number of points close to the upper threshold. What does result from this analysis is a high degree of heterogeneity between the studies ([Q.sub.(40)] = 88,95; p < 0.001) corresponding to over 89% of the variability among them ([I.sub.2] = 55,03%). In this category, 41 results were obtained.

Given this heterogeneity, a random model meta-analysis was applied and a change in the execution of the test was observed as it significantly reduced after the DBS procedure (Z value = -0.406; p < 0.001) (Figure 17). A small effect size was found (Hedges's g = -0.211; SE = 0.039; CI -0.268 to -0.135).

4. Discussion

The results of this study were found to correspond to similar studies in which there is a general reduction of executive brain functions after the DBS procedure. This does not seem to have an impact on quality of life given the improvement of motor symptoms [19, 51, 61]. It is worth highlighting that the study of EF has shown a reduction in tasks such as WCST, verbal fluency, and Stroop in patients with PD before the DBS procedure. This could be explained by alterations in the BG-dorsolateral prefrontal cortex loop in relation to the reduction of dopamine in the nigrostriatal and mesocortical pathways [10].

In general, the study of EF presents a difficulty in terms of the unification of concepts. It has been recognized that the lack of unity in the measurements and significance makes it difficult to establish the relationship with clinical aspects and to explain the improvement or reduction of the functions tested [19]. Following Kudlicka et al. [19], the conclusions are due to the performance in the tests presented without this being an exhaustive analysis of EF. With this, it was found in a number of studies that the same test was used to assess various functions. The lack of representation of Latin American individuals and the lack of studies carried out in Latin America are notable.

The meta-analysis studies and systematic reviews have identified important aspects of PD that could explain part of the emotional functioning, that is, a deficit of emotional recognition which, although not reported in other clinical studies of PD, could help improve communication processes and mood alterations [62]. Such studies can also help us understand the possible relationship between structures such as STN and the structures involved in emotional and cognitive processes [55] and, as such, better understand the disease as a whole.

In the case of the verbal fluency tests, a deterioration has been reported for PD both with pharmacological treatment and with DBS [54]. There is a change in verbal fluency performance with DBS, and this is coherent with other studies and meta-analyses in which a reduction in performance is reported [46, 51, 56]. This alteration has been related to the position of the electrodes on the STN in the left hemisphere [63]. In neuroimaging studies of patients with PD, an associative-type reduction of the metabolic function of the frontal and parietal areas has been found [5], and other studies suggest that the striate nucleus may play a dissociable role in motor control and language cognitive processes, which would mean that different patterns of stimulation would affect the structures of the basal ganglia and cortical regions in different ways. This, in turn, explains why some patients improve in terms of their language articulation and at the same time present a reduction in their verbal fluency after DBS [51]. It has also been reported that the stimulation may cause a decrease of activity in the temporal cortex and inferior frontal areas in the left hemisphere, which would decrease verbal fluency, especially of the phonological kind [64]. Nevertheless, it is necessary to highlight that these hypotheses are still under study.

Inasmuch as heterogeneity, this can be explained based on the variability in the rigorousness of the application and the standardized test to assess it. Given that the reported heterogeneity is close to 45%, it is proposed that the effect detected cannot necessarily be attributed to the DBS procedure.

Inasmuch as cognitive flexibility, the tests assessed do not show a significant change, despite being one of the functions which in other studies is reported as favorable [56]. Similarly, the working memory function has been proposed as one of the aspects that becomes altered in PD. More alterations have been identified in the visuospatial modality than the verbal modality [47, 65], and no significant changes are reported in this study for after DBS.

Inasmuch as the Stroop, no clear effect was identified perhaps due to the high heterogeneity of the studies that may be assumed as being derived from the alternative forms of the test [56].

On the other hand, another type of meta-analysis in PD has been carried out, linking the disease to different levels; for example, a genetic level which shows susceptibility to PD depending on polymorphisms in monoamine oxidase genes (MAO) [66], with other diseases or effects of the transcranial magnetic stimulation [15,27]. This sheds light on the fact that there is a variety of studies that attempt to explain specific aspects of PD, but, as yet, with no unity of analysis that allows us to understand the diversity of the symptoms of patients with PD.

One of the difficulties reported in establishing a STN-DBS effect in systematic changes in the patients and that explains the variability of the effects, as well as the tasks, is the exact location of the electrodes. In this respect, it has been found that although the procedure is carried out in STN, the area of location, the area of active stimulation, or the volume of electrode contact is not always homogeneous [6, 63, 67].

Another of the major difficulties in the systematic assessment of the changes realized by the DBS procedure is the lack of standardized tests to measure the functions [16]. In this study, high variability was found in the versions of some of the tests which could be a factor that contributes to the heterogeneity. On the other hand, it has also been proposed that the alterations presented in PD do not always correlate with the specific alterations related to the treatment (e.g., pharmacological). Thus, the alterations in the different domains and the lack of EF improvement after DBS treatment may respond to a nonlinear model that involves different and complex circuits that are not necessarily modified by STNDBS [68].

Finally, one of the important limitations to detecting of the effects of the procedure is the lack of control or placebo groups that would allow the identification of DBS [56].

http://dx.doi.org/ 10.1155/2017/9641392

Competing Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

This paper was made possible thanks to funding of Vicerrectorla de Investigation of the Pontificia Universidad Javeriana with ID Project: 00006578, titled "Effects of Deep Brain Stimulation (DBS) on Performance of Executive Function Test in Patients with Parkinson's Disease."

References

[1] O. M. Aguilar, C. A. Soto, and M. Esguerra, "Cambios neuropsicoloogicos asociados a estimulacioon cerebral profunda en enfermedad de Parkinson: revision teorica," Suma Psicologica, vol. 18, no. 2, pp. 89-98, 2011.

[2] G. J. Demakis, "The neuropsychology of Parkinson's disease," Disease-a-Month: DM, vol. 53, no. 3, pp. 152-155, 2007.

[3] S. Factor and W. Weiner, Parkinson's Disease: Diagnosis & Clinical Management? Demos Medical, 2nd edition, 2007.

[4] N. A. Haelterman, W. H. Yoon, H. Sandoval, M. Jaiswal, J. M. Shulman, and H. J. Bellen, "A mitocentric view of Parkinson's disease," Annual Review of Neuroscience, vol. 37, pp. 137-159, 2014.

[5] C. Huang, P. Mattis, C. Tang, K. Perrine, M. Carbon, and D. Eidelberg, "Metabolic brain networks associated with cognitive function in Parkinson's disease," Neurolmage, vol. 34, no. 2, pp. 714-723, 2007.

[6] Y. Liu, W. Li, C. Tan et al., "Meta-analysis comparing deep brain stimulation of the globus pallidus and subthalamic nucleus to treat advanced Parkinson disease," Journal of Neurosurgery, vol. 121, no. 3, pp. 709-718, 2014.

[7] A. J. Lees, J. Hardy, and T. Revesz, "Parkinson's disease," The Lancet, vol. 373, no. 9680, pp. 2055-2066, 2009.

[8] K. Wakabayashi, F. Mori, and H. Takahashi, "Progression patterns of neuronal loss and Lewy body pathology in the substantia nigra in Parkinson's disease," Parkinsonism & Related Disorders, vol. 12, no. 2, pp. S92-S98, 2006.

[9] A. L. Bartels and K. L. Leenders, "Parkinson's disease: the syndrome, the pathogenesis and pathophysiology," Cortex, vol. 45, no. 8, pp. 915-921, 2009.

[10] M. C. Rodriguez-Oroz, M. Jahanshahi, P. Krack et al., "Initial clinical manifestations of Parkinson's disease: features and pathophysiological mechanisms," The Lancet Neurology, vol. 8, no. 12, pp. 1128-1139, 2009.

[11] J. M. Chambers and T. J. Prescott, "Response times for visually guided saccades in persons with Parkinson's disease: a meta-analytic review," Neuropsychologia, vol. 48, no. 4, pp. 887-899, 2010.

[12] M. E. Bodden, R. Dodel, and E. Kalbe, "Theory of mind in Parkinson's disease and related basal ganglia disorders: a systematic review," Movement Disorders, vol. 25, no. 1, pp. 13-27, 2010.

[13] T. A. Mestre, A. P. Strafella, T. Thomsen, V. Voon, and J. Miyasaki, "Diagnosis and treatment of impulse control disorders in patients with movement disorders," Therapeutic Advances in Neurological Disorders, vol. 6, no. 3, pp. 175-188, 2013.

[14] J. V. Hindle, A. Martyr, and L. Clare, "Cognitive reserve in Parkinson's disease: a systematic review and meta-analysis," Parkinsonism & Related Disorders, vol. 20, no. 1, pp. 1-7, 2014.

[15] C.-L. Xie, J. Chen, X.-D. Wang et al., "Repetitive transcranial magnetic stimulation (rTMS) for the treatment of depression in Parkinson disease: a meta-analysis of randomized controlled clinical trials," Neurological Sciences, vol. 36, no. 10, pp. 1751-1761, 2015.

[16] M. Denheyer, Z. H. Kiss, and A. M. Haffenden, "Behavioral effects of subthalamic deep brain stimulation in Parkinson's disease," Neuropsychologia, vol. 47, no. 14, pp. 3203-3209, 2009.

[17] V. Voon, K. Hassan, M. Zurowski et al., "Prevalence of repetitive and reward-seeking behaviors in Parkinson disease," Neurology, vol. 67, no. 7, pp. 1254-1257, 2006.

[18] V. Voon, C. Kubu, P. Krack, J.-L. Houeto, and A. I. Troster, "Deep brain stimulation: neuropsychological and neuropsychiatry issues," Movement Disorders, vol. 21, no. S14, pp. S305-S327, 2006.

[19] A. Kudlicka, L. Clare, and J. V. Hindle, "Executive functions in Parkinson's disease: systematic review and meta-analysis," Movement Disorders, vol. 26, no. 13, pp. 2305-2315, 2011.

[20] D. Zgaljardic, J. Borod, N. Foldi et al., "An examination of executive dysfunction associated with frontostriatal circuitry in Parkinson's disease," Journal of Clinical and Experimental Neuropsychology, vol. 28, no. 7, pp. 1127-1144, 2006.

[21] M. E. Bodden, B. Mollenhauer, C. Trenkwalder et al., "Affective and cognitive theory of mind in patients with Parkinson's disease," Parkinsonism & Related Disorders, vol. 16, no. 7, pp. 466-470, 2010.

[22] M. Poletti, I. Enrici, and M. Adenzato, "Cognitive and affective Theory of Mind in neurodegenerative diseases: neuropsychological, neuroanatomical and neurochemical levels," Neuroscience and Biobehavioral Reviews, vol. 36, no. 9, pp. 2147-2164, 2012.

[23] K. L. Parker, D. Lamichhane, M. S. Caetano, and N. S. Narayanan, "Executive dysfunction in Parkinson's disease and timing deficits," Frontiers in Integrative Neuroscience, vol. 7, article 75, 2013.

[24] Y. Smith, T. Wichmann, S. A. Factor, and M. R. Delong, "Parkinson's disease therapeutics: new developments and challenges since the introduction of levodopa," Neuropsychopharmacology, vol. 37, no. 1, pp. 213-246, 2012.

[25] T. M. Cruickshank, A. R. Reyes, and M. R. Ziman, "A systematic review and meta-analysis of strength training in individuals with multiple sclerosis or Parkinson disease," Medicine, vol. 94, no. 4, article e411, 2015.

[26] F. M. Weaver, K. Follett, M. Stern et al., "Bilateral deep brain stimulation vs best medical therapy for patients with advanced parkinson disease: a randomized controlled trial," JAMA-Journal of the American Medical Association, vol. 301, no. 1, pp. 63-73, 2009.

[27] Y.-H. Chou, P. T. Hickey, M. Sundman, A. W. Song, and N.-K. Chen, "Effects of repetitive transcranial magnetic stimulation on motor symptoms in parkinson disease: a systematic review and meta-analysis," JAMA Neurology, vol. 72, no. 4, pp. 432-440, 2015.

[28] H. Zhu, Z. Lu, Y. Jin, X. Duan, J. Teng, and D. Duan, "Low-frequency repetitive transcranial magnetic stimulation on Parkinson motor function: a meta-analysis of randomised controlled trials," Acta Neuropsychiatrica, vol. 27, no. 2, pp. 82-89, 2015.

[29] S. Bickel, L. Alvarez, R. Macias et al., "Cognitive and neuropsychiatric effects of subthalamotomy for Parkinson's disease," Parkinsonism and Related Disorders, vol. 16, no. 8, pp. 535-539, 2010.

[30] F. Agnesi, M. D. Johnson, and J. L. Vitek, "Deep brain stimulation: how does it work?" in Handbook of Clinical Neurology, vol. 116, pp. 39-54, Elsevier, 2013.

[31] A. L. Benabid, S. Chabardes, J. Mitrofanis, and P. Pollak, "Deep brain stimulation of the subthalamic nucleus for the treatment of Parkinson's disease," The Lancet Neurology, vol. 8, no. 1, pp. 67-81, 2009.

[32] G. Giannicola, S. Marceglia, L. Rossi et al., "The effects of levodopa and ongoing deep brain stimulation on subthalamic beta oscillations in Parkinson's disease," Experimental Neurology, vol. 226, no. 1, pp. 120-127, 2010.

[33] M. Jahanshahi, C. R. G. Jones, J. Zijlmans et al., "Dopaminergic modulation of striato-frontal connectivity during motortiming in Parkinson's disease," Brain, vol. 133, part 3, pp. 727-745, 2010.

[34] C. Juri, M. Rodriguez-Oroz, and J. A. Obeso, "The pathophysiological basis of sensory disturbances in Parkinson's disease," Journal of the Neurological Sciences, vol. 289, no. 1-2, pp. 60-65, 2010.

[35] G. Kleiner-Fisman, J. Herzog, D. N. Fisman et al., "Subthalamic nucleus deep brain stimulation: summary and meta-analysis of outcomes," Movement Disorders, vol. 21, supplement 1, pp. S290-304, 2006.

[36] M. K. Lyons, "Deep brain stimulation: current and future clinical applications," Mayo Clinic Proceedings, vol. 86, no. 7, pp. 662-672, 2011.

[37] J. A. Obeso, M. C. Rodriguez-Oroz, M. Rodriguez et al., "Pathophysiology of the basal ganglia in Parkinson's disease," Trends in Neurosciences, vol. 23, no. 10, pp. S8-S19, 2000.

[38] D. Cyron, M. Funk, M.-A. Deletter, and K. Scheufler, "Preserved cognition after deep brain stimulation (DBS) in the subthalamic area for Parkinson's disease: a case report," Acta Neurochirurgica, vol. 152, no. 12, pp. 2097-2100, 2010.

[39] P. Dowsey-Limousin and P. Pollak, "Deep brain stimulation in the treatment of Parkinson's disease: a review and update," Clinical Neuroscience Research, vol. 1, no. 6, pp. 521-526, 2001.

[40] J. M. Nazzaro, R. Pahwa, and K. E. Lyons, "The impact of bilateral subthalamic stimulation on non-motor symptoms of Parkinson's disease," Parkinsonism & Related Disorders, vol. 17, no. 8, pp. 606-609, 2011.

[41] M. Deogaonkar, G. A. Monsalve, J. Scott, A. Ahmed, and A. Rezai, "Bilateral subthalamic deep brain stimulation after bilateral pallidal deep brain stimulation for Parkinson's disease," Stereotactic and Functional Neurosurgery, vol. 89, no. 2, pp. 123-127, 2011.

[42] A. Franzini, R. Cordella, G. Messina et al., "Deep brain stimulation for movement disorders. Considerations on 276 consecutive patients," Journal of Neural Transmission, vol. 118, no. 10, pp. 1497-1510, 2011.

[43] M. D. Johnson, S. Miocinovic, C. C. McIntyre, and J. L. Vitek, "Mechanisms and targets of deep brain stimulation in movement disorders," Neurotherapeutics, vol. 5, no. 2, pp. 294-308, 2008.

[44] P. Limousin and I. Martinez-Torres, "Deep brain stimulation for Parkinson's disease," Neurotherapeutics, vol. 5, no. 2, pp. 309-319, 2008.

[45] F. Weaver, K. Follett, K. Hur, D. Ippolito, and M. Stern, "Deep brain stimulation in Parkinson disease: a metaanalysis of patient outcomes," Journal of Neurosurgery, vol. 103, no. 6, pp. 956-967, 2005.

[46] M. R. Schoenberg, K. M. Mash, K. J. Bharucha, P. C. Francel, and J. G. Scott, "Deep brain stimulation parameters associated with neuropsychological changes in subthalamic nucleus stimulation for refractory Parkinson's disease," Stereotactic and Functional Neurosurgery, vol. 86, no. 6, pp. 337-344, 2008.

[47] R. J. Siegert, M. Weatherall, K. D. Taylor, and D. A. Abernethy, "A meta-analysis of performance on simple span and more complex working memory tasks in Parkinson's disease," Neuropsychology, vol. 22, no. 4, pp. 450-461, 2008.

[48] M. Broen, A. Duits, V. Visser-Vandewalle, Y. Temel, and A. Winogrodzka, "Impulse control and related disorders in Parkinson's disease patients treated with bilateral subthalamic nucleus stimulation: a review," Parkinsonism and Related Disorders, vol. 17, no. 6, pp. 413-417, 2011.

[49] T. Wu and M. Hallett, "The cerebellum in Parkinson's disease," Brain, vol. 136, no. 3, pp. 696-709, 2013.

[50] M. C. Keuken, L. Van Maanen, R. Bogacz et al., "The subthalamic nucleus during decision-making with multiple alternatives," Human Brain Mapping, vol. 36, no. 10, pp. 4041-4052, 2015.

[51] T. D. Parsons, S. A. Rogers, A. J. Braaten, S. P. Woods, and A. I. Troster, "Cognitive sequelae of subthalamic nucleus deep brain stimulation in Parkinson's disease: a meta-analysis," The Lancet Neurology, vol. 5, no. 7, pp. 578-588, 2006.

[52] J. Sanchez-Meca, "Como realizar una revision sistematica y un meta-analisis," Aula Abierta, vol. 38, pp. 53-63, 2010.

[53] A. Liberati, D. G. Altman, J. Tetzlaff et al., "The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration," PLoS Medicine, vol. 6, no. 7, Article ID e1000100, 2009.

[54] L. Castelli, M. Lanotte, M. Zibetti et al., "Apathy and verbal fluency in STN-stimulated PD patients: An Observational Follow-up Study," Journal of Neurology, vol. 254, no. 9, pp. 1238-1243, 2007.

[55] F. Le Jeune, J. Peron, I. Biseul et al., "Subthalamic nucleus stimulation affects orbitofrontal cortex in facial emotion recognition: A Pet Study," Brain, vol. 131, no. 6, pp. 1599-1608, 2008.

[56] K. Witt, C. Daniels, J. Reiff et al., "Neuropsychological and psychiatric changes after deep brain stimulation for Parkinson's disease: a randomised, multicentre study," The Lancet Neurology, vol. 7, no. 7, pp. 605-614, 2008.

[57] L. Yang, G.-D. Zhan, J.-J. Ding et al., "Psychiatric illness and intellectual disability in the prader-willi syndrome with different molecular defects--a meta analysis," PLoS ONE, vol. 8, no. 8, Article ID e72640, 2013.

[58] J. A. C. Sterne and M. Egger, "Funnel plots for detecting bias in meta-analysis: guidelines on choice of axis," Journal of Clinical Epidemiology, vol. 54, no. 10, pp. 1046-1055, 2001.

[59] M. Borenstein, L. V. Hedges, J. P. T. Higgins, and H. R. Rothstein, "A basic introduction to fixed- effect and random-effects models for meta-analysis," Research Synthesis Methods, vol. 1, no. 2, pp. 97-111, 2010.

[60] B. T. Johnson, L. A. J. Scott-Sheldon, L. B. Snyder, S. M. Noar, and T. B. Huedo-Medina, "Contemporary approaches to metaanalysis in communication research: SAGE research methods," in The SAGE Sourcebook of Advanced Data Analysis Methods for Communication Research, A. F. Hayes, M. D. Slater, and L. B. Snyder, Eds., SAGE, Los Angeles, Calif, USA, 2008.

[61] B. Wu, L. Han, B.-M. Sun, X.-W. Hu, and X.-P. Wang, "Influence of deep brain stimulation of the subthalamic nucleus on cognitive function in patients with Parkinson's disease," Neuroscience Bulletin, vol. 30, no. 1, pp. 153-161, 2014.

[62] H. M. Gray and L. Tickle-Degnen, "A meta-analysis of performance on emotion recognition tasks in Parkinson's disease," Neuropsychology, vol. 24, no. 2, pp. 176-191, 2010.

[63] M. K. York, E. A. Wilde, R. Simpson, and J. Jankovic, "Relationship between neuropsychological outcome and DBS surgical trajectory and electrode location," Journal of the Neurological Sciences, vol. 287, no. 1-2, pp. 159-171, 2009.

[64] A. Fasano, A. Daniele, and A. Albanese, "Treatment of motor and non-motor features of Parkinson's disease with deep brain stimulation," The Lancet Neurology, vol. 11, no. 5, pp. 429-442, 2012.

[65] M. L. Waterfall and S. F. Crowe, "Meta-analytic comparison of the components of visual cognition in Parkinson's disease," Journal of Clinical and Experimental Neuropsychology, vol. 17, no. 5, pp. 759-772, 1995.

[66] Y.-X. Sun, X.-H. Wang, A.-H. Xu, and J.-H. Zhao, "Functional polymorphisms of the MAO gene with Parkinson disease susceptibility: a meta-analysis," Journal of the Neurological Sciences, vol. 345, no. 1, pp. 97-105, 2014.

[67] F. Caire, D. Ranoux, D. Guehl, P. Burbaud, and E. Cuny, "A systematic review of studies on anatomical position of electrode contacts used for chronic subthalamic stimulation in Parkinson's disease," Acta Neurochirurgica, vol. 155, no. 9, pp. 1647-1654, 2013.

[68] R. Pavao, A. F. Helene, and G. F. Xavier, "Parkinson's disease progression: implicit acquisition, cognitive and motor impairments, and medication effects," Frontiers in Integrative Neuroscience, vol. 6, article 56, 2012.

A. M. Martinez-Martinez, (1) O. M. Aguilar, (2) and C. A. Acevedo-Triana (1)

(1) Department of Psychology, Pontificia Universidad Javeriana, Bogota, Colombia

(2) Department of Brain Repair and Rehabilitation, University College London, London, UK

Correspondence should be addressed to C. A. Acevedo-Triana; cesar.acevedo@javeriana.edu.co

Received 25 August 2016; Accepted 11 October 2016; Published 8 February 2017

Academic Editor: Rajka M. Liscic

Caption: FIGURE 1: Flow diagram of study selection. Adapted from Liberati et al. [53].

Caption: FIGURE 2: Funnel plot for standard error in publications of verbal fluency.

Caption: FIGURE 4: Funnel plot for standard error in publications of cognitive flexibility (WSCT).

Caption: FIGURE 6: Funnel plot for standard error in publications of Trail Making Test (TMT-A).

Caption: FIGURE 8: Funnel plot for standard error in publications of Trail Making Test (TMT-B).

Caption: FIGURE 10: Funnel plot for standard error in publications of Trail Making Test (TMT-AB).

Caption: Figure 12: Funnel plot for standard error in publications of Raven Matrix.

Caption: FIGURE 14: Funnel plot for standard error in publications of Digit Span Test (DST).

Caption: FIGURE 16: Funnel plot for standard error in publications of Stroop Test.
TABLE 1: Demographic and clinical aspects of patients in studies and
frequency of neuropscyhological tests.

Study                               N      Country

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)    30       Japan
Daniels (2012)                     60      Germany
Castelli et al. [54]               19       Italy
Zangaglia et al. (2009)            65       Italy
Tang (2015)                        27       China
Rothlind (2015)                    164       USA
Houvenaghel (2015)                 26      France
Tramontana (2015)                  30        USA

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)           30       Japan
Merolaetal., (2011)                20       Italy
Daniels etal., 2010                60      Germany
Castelli et al., [54]              19       Italy
Le Jeune et al. [55]               13      France
Saez-Zea, et al. (2012)             9       Spain
Castelli et al., (2010)            27       Italy
Rothlind (2015)                    164       USA
Houvenaghel (2015)                 26      France
Tramontana (2015)                  30        USA

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)                   32       Italy
Fraraccio, (2008)                  15      Canada
Williams et al. (2011)             19        USA
Rothlind (2015)                    164       USA
Tramontana (2015)                  30        USA

Nelson Modified WSCT

Castelli et al. [54]               19       Italy
Castelli, (2010)                   27       Italy
Fasano (2010)                      20       Italy
Lejuene, (2010)                    13      France
Le Jeune et al., [55]              13      France
Houvenaghel (2015)                 26      France

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)           30       Japan
Merola (2011)                      20       Italy
Williams (2011)                    19        USA
Castelli et al. [54]               19       Italy
Lejuene, (2010)                    13      France
Le Jeune et al. [55]               13      France
Castelli, (2010)                   27       Italy
Smeding et al. (2005)              20    Netherlands
Rothlind (2015)                    164       USA
Houvenaghel (2015)                 26      France

Corsi Span Backward

Takehiko-Yamanaka (2012)           30       Japan
Smeding, (2005)                    20    Netherlands
Fasano (2010)                      20       Italy
Castelli et al. [54]               19       Italy
Castelli, (2010)                   27       Italy

Takehiko-Yamanaka (2012)           30       Japan
Daniels (2010)                     60      Germany
Fasano (2010)                      20       Italy
Fraraccio, (2008)                  15      Canada
Witt et al. [56]                   60      Germany
Rothlind, et al. (2007)            29        USA
Zangaglia (2009)                   32       Italy
Rothlind (2015)                    164       USA
Tang (2015)                        27       China

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)           30       Japan
Smeding, (2005)                    20    Netherlands
Williams (2011)                    19        USA
Williams (2011)                    19        USA
Daniels (2010)                     60      Germany
Smeding, (2005)                    20    Netherlands
Moreines, (2014)                   17
Fraraccio, (2008)                  15      Canada
Le Jeune et al. [55]               13      France
Rothlind, (2007)                   29        USA
Lejuene, (2010)                    13      France
Witt et al. [56]                   60      Germany
Rothlind (2015)                    164       USA
Houvenaghel (2015)                 26      France
Tramontana (2015)                  30        USA

Planification

Zangaglia (2009)                   65       Italy
Castelli, (2010)                   27       Italy
Fasano (2010)                      20       Italy
Castelli et al. [54]               19       Italy

Study                                    Design             Target

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)         Pre-post             STN
Daniels (2012)                     Pre-post + control        STN
Castelli et al. [54]                    Pre-post             STN
Zangaglia et al. (2009)            Pre-post + control        STN
Tang (2015)                             Pre-post             STN
Rothlind (2015)                    Pre-post + control     STN + GPi
Houvenaghel (2015)                 Pre-post + control        STN
Tramontana (2015)                  Pre-post + control   STN + medicine

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)                Pre-post             STN
Merolaetal., (2011)                Pre-post + control    STN + OTHER
Daniels etal., 2010                Pre-post + control        STN
Castelli et al., [54]                   Pre-post             STN
Le Jeune et al. [55]               Pre-post + control        STN
Saez-Zea, et al. (2012)                 Pre-post             STN
Castelli et al., (2010)                 Pre-post             STN
Rothlind (2015)                    Pre-post + control     STN + GPi
Houvenaghel (2015)                 Pre-post + control        STN
Tramontana (2015)                  Pre-post + control   STN + medicine

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)                   Pre-post + control        STN
Fraraccio, (2008)                        On-off              STN
Williams et al. (2011)                    Post               STN
Rothlind (2015)                    Pre-post + control     STN + GPi
Tramontana (2015)                  Pre-post + control   STN + medicine

Nelson Modified WSCT

Castelli et al. [54]                    Pre-post             STN
Castelli, (2010)                        Pre-post             STN
Fasano (2010)                           Pre-post             STN
Lejuene, (2010)                         Pre-post             STN
Le Jeune et al., [55]              Pre-post + control        STN
Houvenaghel (2015)                 Pre-post + control        STN

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)                Pre-post             STN
Merola (2011)                      Pre-post + control    STN + OTHER
Williams (2011)                           Post               STN
Castelli et al. [54]                    Pre-post             STN
Lejuene, (2010)                         Pre-post             STN
Le Jeune et al. [55]               Pre-post + control        STN
Castelli, (2010)                       Pre-post              STN
Smeding et al. (2005)              Pre-post + control      STN + GP
Rothlind (2015)                    Pre-post + control     STN + GPi
Houvenaghel (2015)                 Pre-post + control        STN

Corsi Span Backward

Takehiko-Yamanaka (2012)                Pre-post             STN
Smeding, (2005)                    Pre-post + control        STN
Fasano (2010)                           Pre-post             STN
Castelli et al. [54]                    Pre-post             STN
Castelli, (2010)                        Pre-post             STN

Takehiko-Yamanaka (2012)                Pre-post             STN
Daniels (2010)                     Pre-post + control        STN
Fasano (2010)                           Pre-post             STN
Fraraccio, (2008)                        On-off              STN
Witt et al. [56]                   Pre-post + control        STN
Rothlind, et al. (2007)                 On-off             STN + GP
Zangaglia (2009)                   Pre-post + control        STN
Rothlind (2015)                    Pre-post + control     STN + GPi
Tang (2015)                             Pre-post             STN

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)                Pre-post             STN
Smeding, (2005)                    Pre-post + Control      STN + GP
Williams (2011)                           Post               STN
Williams (2011)                           Post               STN
Daniels (2010)                     Pre-post + control        STN
Smeding, (2005)                    Pre-post + control      STN + GP
Moreines, (2014)                        Pre-post             OTH
Fraraccio, (2008)                        On-off              STN
Le Jeune et al. [55]               Pre-post + Control        STN
Rothlind, (2007)                         On-off            STN + GP
Lejuene, (2010)                         Pre-post             STN
Witt et al. [56]                   Pre-post + Control        STN
Rothlind (2015)                    Pre-post + control     STN + GPi
Houvenaghel (2015)                 Pre-post + control        STN
Tramontana (2015)                  Pre-post + control   STN + medicam

Planification

Zangaglia (2009)                   Pre-post + control        STN
Castelli, (2010)                        Pre-post             STN
Fasano (2010)                           Pre-post             STN
Castelli et al. [54]                    Pre-post             STN

Study                                    Age

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)      61,1 (9,1)
Daniels (2012)                       60,2 (7,9)
Castelli et al. [54]                 62,1 (4,2)
Zangaglia et al. (2009)             58,84 (7,70)
Tang (2015)
Rothlind (2015)                      62,3 (8,9)
Houvenaghel (2015)                   55,8 (6,2)
Tramontana (2015)                       60(7)

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)             61,1 (9,1)
Merolaetal., (2011)                  66,5 (2,5)
Daniels etal., 2010                  60,2 (7,9)
Castelli et al., [54]                62,1 (4,2)
Le Jeune et al. [55]                  57 (7,8)
Saez-Zea, et al. (2012)                54 (14)
Castelli et al., (2010)              60,6 (6,7)
Rothlind (2015)                      62,3 (8,9)
Houvenaghel (2015)                   55,8 (6,2)
Tramontana (2015)                       60(7)

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)                    58,84 (7,70)
Fraraccio, (2008)                    58,1 (7,46)
Williams et al. (2011)               62,1 (10,3)
Rothlind (2015)                      62,3 (8,9)
Tramontana (2015)                       60(7)

Nelson Modified WSCT

Castelli et al. [54]                 62,1 (4,2)
Castelli, (2010)                     60,6 (6,7)
Fasano (2010)                        56,9 (7,2)
Lejuene, (2010)                       57 (7,8)
Le Jeune et al., [55]                 57 (7,8)
Houvenaghel (2015)                   55,8 (6,2)

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)             61,1 (9,1)
Merola (2011)                        66,5 (2,5)
Williams (2011)                      62,1 (10,3)
Castelli et al. [54]                 62,1 (4,2)
Lejuene, (2010)                       57 (7,8)
Le Jeune et al. [55]                  57 (7,8)
Castelli, (2010)                     60,6 (6,7)
Smeding et al. (2005)                59,2 (8,6)
Rothlind (2015)                      62,3 (8,9)
Houvenaghel (2015)                   55,8 (6,2)

Corsi Span Backward

Takehiko-Yamanaka (2012)             61,1 (9,1)
Smeding, (2005)                      59,2 (8,6)
Fasano (2010)                        56,9 (7,2)
Castelli et al. [54]                 62,1 (4,2)
Castelli, (2010)                     60,6 (6,7)

                                   Backward digits

Takehiko-Yamanaka (2012)             61,1 (9,1)
Daniels (2010)                       60,2 (7,9)
Fasano (2010)                        56,9 (7,2)
Fraraccio, (2008)                    58,1 (7,46)
Witt et al. [56]                     60,2 (7,9)
Rothlind, et al. (2007)             61,4 (10,11)
Zangaglia (2009)                    58,84 (7,70)
Rothlind (2015)                      62,3 (8,9)
Tang (2015)

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)             61.1 (9,1)
Smeding, (2005)                      59.2 (8,6)
Williams (2011)                      62,1 (10,3)
Williams (2011)                      62,1 (10,3)
Daniels (2010)                       60,2 (7,9)
Smeding, (2005)                      59,2 (8,6)
Moreines, (2014)                          1
Fraraccio, (2008)                    58,1 (7,46)
Le Jeune et al. [55]                  57 (7,8)
Rothlind, (2007)                    61,4 (10,11)
Lejuene, (2010)                       57 (7,8)
Witt et al. [56]                     60,2 (7,9)
Rothlind (2015)                      62,3 (8,9)
Houvenaghel (2015)                   55,8 (6,2)
Tramontana (2015)                       60(7)

Planification

Zangaglia (2009)                    58,84 (7,70)
Castelli, (2010)                     60,6 (6,7)
Fasano (2010)                        56,9 (7,2)
Castelli et al. [54]                 62,1 (4,2)

                                       Education            Onset
Study                                   (years)           Parkinson
                                                           disease

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)        12,5(4,5)          11,5 (5,7)
Daniels (2012)                             --             13,8 (6,3)
Castelli et al. [54]                       --              14,7 (5)
Zangaglia et al. (2009)               7,31 (3,21)        11,84 (5,07)
Tang (2015)
Rothlind (2015)                         14,8 (3)          12,8 (5,5)
Houvenaghel (2015)                     10,1 (2,4)          11,7 (4)
Tramontana (2015)                          --             2,2 (1,4)

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)               12,5 (4,5)         11,5 (5,7)
Merolaetal., (2011)                        --             16,4 (4,3)
Daniels etal., 2010                        --             13,8 (6,3)
Castelli et al., [54]                      --              14,7 (5)
Le Jeune et al. [55]                       --             10,9 (2,2)
Saez-Zea, et al. (2012)                    --               12 (2)
Castelli et al., (2010)                 8 (4,1)           15,3 (5,1)
Rothlind (2015)                         14,8 (3)          12,8 (5,5)
Houvenaghel (2015)                     10,1 (2,4)          11,7 (4)
Tramontana (2015)                          --             2,2 (1,4)

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)                      7,31 (3,21)        11,84 (5,07)
Fraraccio, (2008)                     11,3 (3,97)        13,6 (4,39)
Williams et al. (2011)                13,6 (1,71)        10,1 (6,24)
Rothlind (2015)                         14,8 (3)          12,8 (5,5)
Tramontana (2015)                          --             2,2 (1,4)

Nelson Modified WSCT

Castelli et al. [54]                       --              14,7 (5)
Castelli, (2010)                        8 (4,1)           15,3 (5,1)
Fasano (2010)                              --             13,7 (4,8)
Lejuene, (2010)                            --             10,9 (2,2)
Le Jeune et al., [55]                      --             10,9 (2,2)
Houvenaghel (2015)                     10,1 (2,4)          11,7 (4)

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)               12,5 (4,5)         11,5 (5,7)
Merola (2011)                              --             16,4 (4,3)
Williams (2011)                       13,6 (1,71)        10,1 (6,24)
Castelli et al. [54]                       --              14,7 (5)
Lejuene, (2010)                            --             10,9 (2,2)
Le Jeune et al. [55]                       --             10,9 (2,2)
Castelli, (2010)                        8 (4,1)           15,3 (5,1)
Smeding et al. (2005)                  10,7 (1,9)         12 (3-50)
Rothlind (2015)                         14,8 (3)          12,8 (5,5)
Houvenaghel (2015)                     10,1 (2,4)          11,7 (4)

Corsi Span Backward

Takehiko-Yamanaka (2012)               12,5 (4,5)       ird 11,5 (5,7)
Smeding, (2005)                        10,7 (1,9)       ward 12 (3-50)
Fasano (2010)                              --             13,7 (4,8)
Castelli et al. [54]                       --              14,7 (5)
Castelli, (2010)                        8 (4,1)           15,3 (5,1)

Takehiko-Yamanaka (2012)               12,5 (4,5)         11,5 (5,7)
Daniels (2010)                             --             13,8 (6,3)
Fasano (2010)                              --             13,7 (4,8)
Fraraccio, (2008)                     11,3 (3,97)        13,6 (4,39)
Witt et al. [56]                           --             13,8 (6,3)
Rothlind, et al. (2007)               15,2 (3,21)         12,9 (4,3)
Zangaglia (2009)                      7,31 (3,21)        11,84 (5,07)
Rothlind (2015)                         14,8 (3)          12,8 (5,5)
Tang (2015)

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)               12,5 (4,5)         11,5 (5,7)
Smeding, (2005)                        10,7 (1,9)         12 (3-50)
Williams (2011)                       13,6 (1,71)        10,1 (6,24)
Williams (2011)                    Stroop 13,6 (1,71)     10,1(6,24)
Daniels (2010)                             --             13,8 (6,3)
Smeding, (2005)                        10,7 (1,9)         12 (3-50)
Moreines, (2014)                                              2
Fraraccio, (2008)                     11,3 (3,97)        13,6 (4,39)
Le Jeune et al. [55]                       --             10,9 (2,2)
Rothlind, (2007)                      15,2 (3,21)         12,9 (4,3)
Lejuene, (2010)                            --             10,9 (2,2)
Witt et al. [56]                           --             13,8 (6,3)
Rothlind (2015)                         14,8 (3)          12,8 (5,5)
Houvenaghel (2015)                     10,1 (2,4)          11,7 (4)
Tramontana (2015)                          --             2,2 (1,4)

Planification

Zangaglia (2009)                      7,31 (3,21)        11,84 (5,07)
Castelli, (2010)                        8 (4,1)           15,3 (5,1)
Fasano (2010)                              --             13,7 (4,8)
Castelli et al. [54]                       --              14,7 (5)

                                   Hoehn & Yahr        Time to
Study                                  stage       postevaluation
                                                      in months

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)         --              1,12
Daniels (2012)                      2,29 (0,72)           6
Castelli et al. [54]                    --               17
Zangaglia et al. (2009)             2,34 (0,43)    1, 6,12, 24, 36
Tang (2015)                                             6,12
Rothlind (2015)                      3,3(0,9)             6
Houvenaghel (2015)                   1,8 (0,8)            3
Tramontana (2015)                        2             6 y 12

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)                --              1,12
Merolaetal., (2011)                     --               14
Daniels etal., 2010                 2,29 (0,72)           6
Castelli et al., [54]                   --               17
Le Jeune et al. [55]                    --               --
Saez-Zea, et al. (2012)                  3
Castelli et al., (2010)                 --                1
Rothlind (2015)                      3,3(0,9)             6
Houvenaghel (2015)                   1,8 (0,8)            3
Tramontana (2015)                        2             6 y 12

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)                    2,34 (0,43)    1, 6,12, 24, 36
Fraraccio, (2008)                       --               19
Williams et al. (2011)               1,5-3,0             24
Rothlind (2015)                      3,3(0,9)             6
Tramontana (2015)                        2             6 y 12

Nelson Modified WSCT

Castelli et al. [54]                    --               17
Castelli, (2010)                        --                1
Fasano (2010)                            3               5,8
Lejuene, (2010)                         --                3
Le Jeune et al., [55]                   --               --
Houvenaghel (2015)                   1,8 (0,8)            3

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)                --              1,12
Merola (2011)                           --               14
Williams (2011)                      1,5--3,0            24
Castelli et al. [54]                    --               17
Lejuene, (2010)                         --                3
Le Jeune et al. [55]                    --               --
Castelli, (2010)                        2,5              1
Smeding et al. (2005)                (1,0-5,0)          6,12
Rothlind (2015)                      3,3(0,9)             6
Houvenaghel (2015)                   1,8 (0,8)            3

Corsi Span Backward

Takehiko-Yamanaka (2012)                                1,12
Smeding, (2005)                    2,5 (1,0-5,0)        6,12
Fasano (2010)                            3               5,8
Castelli et al. [54]                    --               17
Castelli, (2010)                        --                1

Takehiko-Yamanaka (2012)                --              1,12
Daniels (2010)                      2,29 (0,72)          --
Fasano (2010)                            3               5,8
Fraraccio, (2008)                       --               19
Witt et al. [56]                    3,62 (0,85)           6
Rothlind, et al. (2007)             3,3 (0,45)           --
Zangaglia (2009)                    2,34 (0,43)    1, 6,12, 24, 36
Rothlind (2015)                      3,3(0,9)             6
Tang (2015)                                             6,12

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)                --              1,12
Smeding, (2005)                    2,5 (1,0-5,0)        6,12
Williams (2011)                       1,5-3,0            24
Williams (2011)                       1,5-3,0            24
Daniels (2010)                      2,29 (0,72)          --
Smeding, (2005)                    2,5 (1,0-5,0)         6,1
Moreines, (2014)                                         --
Fraraccio, (2008)                       --               19
Le Jeune et al. [55]                    --               --
Rothlind, (2007)                    3,3 (0,45)           --
Lejuene, (2010)                         --                3
Witt et al. [56]                    3,62 (0,85)           6
Rothlind (2015)                      3,3(0,9)             6
Houvenaghel (2015)                   1,8 (0,8)            3
Tramontana (2015)                        2              6,12

Planification

Zangaglia (2009)                    2,34 (0,43)    1, 6,12, 24, 36
Castelli, (2010)                        --                1
Fasano (2010)                            3               5,8
Castelli et al. [54]                    --               17

Study                                            Pulse

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)               90 [micro]s
Daniels (2012)                                60 [micro]s
Castelli et al. [54]               Right 61,6 (6,9), left 61,6 (6,9)
Zangaglia et al. (2009)
Tang (2015)                                        --
Rothlind (2015)                                    --
Houvenaghel (2015)                                 --
Tramontana (2015)                                  --

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)                       90[micro]s
Merolaetal., (2011)                                --
Daniels etal., 2010                           60 [micro]s
Castelli et al., [54]              Right 61,6 (6,9), left 61,6 (6,9)
Le Jeune et al. [55]                              64,6
Saez-Zea, et al. (2012)                            --
Castelli et al., (2010)                            --
Rothlind (2015)                                    --
Houvenaghel (2015)                                 --
Tramontana (2015)                                  --

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)
Fraraccio, (2008)                       Left: 94,0, right: 94,0
Williams et al. (2011)                             --
Rothlind (2015)                                    --
Tramontana (2015)                                  --

Nelson Modified WSCT

Castelli et al. [54]               Right 61,6 (6,9), left 61,6 (6,9)
Castelli, (2010)                                   --
Fasano (2010)                                 60 [micro]s
Lejuene, (2010)                            2,7 ([+ or -] 0,5)
Le Jeune et al., [55]                             64,6
Houvenaghel (2015)                                 --

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)                      90 [micro]s
Merola (2011)                                      --
Williams (2011)                                    --
Castelli et al. [54]               Right 61,6 (6,9), left 61,6 (6,9)
Lejuene, (2010)                            2,7 ([+ or -] 0,5)
Le Jeune et al. [55]                              64,6
Castelli, (2010)                                   --
Smeding et al. (2005)                              --
Rothlind (2015)                                    --
Houvenaghel (2015)                                 --

Corsi Span Backward

Takehiko-Yamanaka (2012)                      90 [micro]s
Smeding, (2005)                                    --
Fasano (2010)                                 60 [micro]s
Castelli et al. [54]                Right 61,6 (6,9), left 61,6(6,9)
Castelli, (2010)                                   --

Takehiko-Yamanaka (2012)                      90 [micro]s
Daniels (2010)                                60 [micro]s
Fasano (2010)                                 60 [micro]s
Fraraccio, (2008)                       Left: 94,0, right: 94,0
Witt et al. [56]                                   --
Rothlind, et al. (2007)                            --
Zangaglia (2009)
Rothlind (2015)                                    --
Tang (2015)                                        --

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)                      90 [micro]s
Smeding, (2005)                                    --
Williams (2011)                                    --
Williams (2011)                                    --
Daniels (2010)                                60 [micro]s
Smeding, (2005)                                    --
Moreines, (2014)                              91 [micro]s
Fraraccio, (2008)                       Left: 94,0, right: 94,0
Le Jeune et al. [55]                              64,6
Rothlind, (2007)                                   --
Lejuene, (2010)                            2,7 ([+ or -] 0,5)
Witt et al. [56]                                   --
Rothlind (2015)                                    --
Houvenaghel (2015)                                 --
Tramontana (2015)                                  --

Planification

Zangaglia (2009)
Castelli, (2010)                                   --
Fasano (2010)                                 60 [micro]s
Castelli et al. [54]               Right 61,6 (6,9), left 61,6 (6,9)

Study                                       Frequency

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)              130 Hz
Daniels (2012)                               130 Hz
Castelli et al. [54]
Zangaglia et al. (2009)
Tang (2015)                                    --
Rothlind (2015)                                --
Houvenaghel (2015)                             --
Tramontana (2015)                              --

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)                     130 Hz
Merolaetal., (2011)                            --
Daniels etal., 2010                          130 Hz
Castelli et al., [54]
Le Jeune et al. [55]                 R 135,3 Hz, L 136,5 Hz
Saez-Zea, et al. (2012)                        --
Castelli et al., (2010)                        --
Rothlind (2015)                                --
Houvenaghel (2015)                             --
Tramontana (2015)                              --

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)
Fraraccio, (2008)                  Left: 185 Hz, right: 185 Hz
Williams et al. (2011)                         --
Rothlind (2015)                                --
Tramontana (2015)                              --

Nelson Modified WSCT

Castelli et al. [54]
Castelli, (2010)                               --
Fasano (2010)                                130 Hz
Lejuene, (2010)                       68,7 ([+ or -] 13,9)
Le Jeune et al., [55]                R 135,3 Hz, L 136,5 Hz
Houvenaghel (2015)                             --

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)                     130 Hz
Merola (2011)                                  --
Williams (2011)                                --
Castelli et al. [54]
Lejuene, (2010)                       68,7 ([+ or -] 13,9)
Le Jeune et al. [55]                 R 135,3 Hz, L 136,5 Hz
Castelli, (2010)                               --
Smeding et al. (2005)                          --
Rothlind (2015)                                --
Houvenaghel (2015)                             --

Corsi Span Backward

Takehiko-Yamanaka (2012)                     130 Hz
Smeding, (2005)                                --
Fasano (2010)                                130 Hz
Castelli et al. [54]
Castelli, (2010)                               --

Takehiko-Yamanaka (2012)                     130 Hz
Daniels (2010)                               130 Hz
Fasano (2010)                                130 Hz
Fraraccio, (2008)                  Left: 185 Hz, right: 185 Hz
Witt et al. [56]                               --
Rothlind, et al. (2007)                        --
Zangaglia (2009)
Rothlind (2015)                                --
Tang (2015)                                    --

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)                     130 Hz
Smeding, (2005)                                --
Williams (2011)                                --
Williams (2011)                                --
Daniels (2010)                               130 Hz
Smeding, (2005)                                --
Moreines, (2014)                             130 Hz
Fraraccio, (2008)                  Left: 185 Hz, right: 185 Hz
Le Jeune et al. [55]                 R 135,3 Hz, L 136,5 Hz
Rothlind, (2007)                               --
Lejuene, (2010)                       68,7 ([+ or -] 13,9)
Witt et al. [56]                               --
Rothlind (2015)                                --
Houvenaghel (2015)                             --
Tramontana (2015)                              --

Planification

Zangaglia (2009)
Castelli, (2010)                               --
Fasano (2010)                                130 Hz
Castelli et al. [54]

Study                                          Voltage

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)                  2,4
Daniels (2012)                                    --
Castelli et al. [54]               Right 3,2 (0,4), left 3,2 (0,5)
Zangaglia et al. (2009)
Tang (2015)                                       --
Rothlind (2015)                                   --
Houvenaghel (2015)                                --
Tramontana (2015)                                 --

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)                        2,4 V
Merolaetal., (2011)                               --
Daniels etal., 2010                               --
Castelli et al., [54]              Right 3,2 (0,4), left 3,2 (0,5)
Le Jeune et al. [55]                   Right 2,3 Vy, left 2,4 V
Saez-Zea, et al. (2012)                           --
Castelli et al., (2010)                           --
Rothlind (2015)                                   --
Houvenaghel (2015)                                --
Tramontana (2015)                                 --

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)
Fraraccio, (2008)                       Left: 2,8, right: 2,8
Williams et al. (2011)                            --
Rothlind (2015)                                   --
Tramontana (2015)                                 --

Nelson Modified WSCT

Castelli et al. [54]               right 3,2 (0,4), left 3,2 (0,5)
Castelli, (2010)                                  --
Fasano (2010)                                     --
Lejuene, (2010)                          38,1 ([+ or -] 17,1)
Le Jeune et al., [55]                  Right 2,3 V, left 2,4 V
Houvenaghel (2015)                                --

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)                        2,4 V
Merola (2011)                                     --
Williams (2011)                                   --
Castelli et al. [54]               Right 3,2 (0,4), left 3,2 (0,5)
Lejuene, (2010)                          38,1 ([+ or -] 17,1)
Le Jeune et al. [55]                   Right 2,3 Vy, left 2,4 V
Castelli, (2010)                                  --
Smeding et al. (2005)                             --
Rothlind (2015)                                   --
Houvenaghel (2015)                                --

Corsi Span Backward

Takehiko-Yamanaka (2012)                        2,4 V
Smeding, (2005)                                   --
Fasano (2010)                                     --
Castelli et al. [54]               right 3,2 (0,4), left 3,2 (0,5)
Castelli, (2010)                                  --

Takehiko-Yamanaka (2012)                        2,4 V
Daniels (2010)                          Adjusted for each one
Fasano (2010)                                     --
Fraraccio, (2008)                       Left: 2,8, right: 2,8
Witt et al. [56]                                  --
Rothlind, et al. (2007)                           --
Zangaglia (2009)
Rothlind (2015)                                   --
Tang (2015)                                       --

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)                        2,4 V
Smeding, (2005)                                   --
Williams (2011)                                   --
Williams (2011)                                   --
Daniels (2010)                          Adjusted for each one
Smeding, (2005)                                   --
Moreines, (2014)                                  --
Fraraccio, (2008)                       Left: 2,8, right: 2,8
Le Jeune et al. [55]                   Right 2,3 Vy, left 2,4 V
Rothlind, (2007)                                  --
Lejuene, (2010)                          38,1 ([+ or -] 17,1)
Witt et al. [56]                                  --
Rothlind (2015)                                   --
Houvenaghel (2015)                                --
Tramontana (2015)                                 --

Planification

Zangaglia (2009)
Castelli, (2010)                                  --
Fasano (2010)                                     --
Castelli et al. [54]               Right 3,2 (0,4), left 3,2 (0,5)

Study                                    Electrodes

Verb fluency-semantic

Takehiko-Yamanaka et al. (2012)          Monopolar
Daniels (2012)
Castelli et al. [54]                Monopolar bilateral
Zangaglia et al. (2009)            Semimicro e lec tro de
Tang (2015)                              Bilateral
Rothlind (2015)                          Bilateral
Houvenaghel (2015)                       Bilateral
Tramontana (2015)                        Bilateral

Verb fluency-phoenemic

Takehiko-Yamanaka (2012)                 Monopolar
Merolaetal., (2011)                          --
Daniels etal., 2010
Castelli et al., [54]               Monopolar bilateral
Le Jeune et al. [55]                    Quadripolar
Saez-Zea, et al. (2012)
Castelli et al., (2010)
Rothlind (2015)                          Bilateral
Houvenaghel (2015)                       Bilateral
Tramontana (2015)                        Bilateral

Wisconsin Card Sorting Test (WCST)

Zangaglia (2009)                     Semimicroelectrode
Fraraccio, (2008)                       Quadripolar
Williams et al. (2011)                       --
Rothlind (2015)                          Bilateral
Tramontana (2015)                        Bilateral

Nelson Modified WSCT

Castelli et al. [54]                Monopolar bilateral
Castelli, (2010)                             --
Fasano (2010)                                --
Lejuene, (2010)                         Quadripolar
Le Jeune et al., [55]                   Quadripolar
Houvenaghel (2015)                       Bilateral

Trail Making Test (TMT-B)

Takehiko-Yamanaka (2012)                 Monopolar
Merola (2011)                                --
Williams (2011)                              --
Castelli et al. [54]                Monopolar bilateral
Lejuene, (2010)                         Quadripolar
Le Jeune et al. [55]                    Quadripolar
Castelli, (2010)                             --
Smeding et al. (2005)                        --
Rothlind (2015)                          Bilateral
Houvenaghel (2015)                       Bilateral

Corsi Span Backward

Takehiko-Yamanaka (2012)                 Monopolar
Smeding, (2005)                              --
Fasano (2010)                                --
Castelli et al. [54]                Monopolar bilateral
Castelli, (2010)

Takehiko-Yamanaka (2012)                 Monopolar
Daniels (2010)                           Bilateral
Fasano (2010)                                --
Fraraccio, (2008)                       Quadripolar
Witt et al. [56]                             --
Rothlind, et al. (2007)                      --
Zangaglia (2009)                   Semimicro e lec tro de
Rothlind (2015)                          Bilateral
Tang (2015)                              Bilateral

Trail Making Test (TMT-A)

Takehiko-Yamanaka (2012)                 Monopolar
Smeding, (2005)                              --
Williams (2011)                              --
Williams (2011)                              --
Daniels (2010)                           Bilateral
Smeding, (2005)                              --
Moreines, (2014)                             --
Fraraccio, (2008)                       Quadripolar
Le Jeune et al. [55]                    Quadripolar
Rothlind, (2007)                             --
Lejuene, (2010)                         Quadripolar
Witt et al. [56]                             --
Rothlind (2015)                          Bilateral
Houvenaghel (2015)                       Bilateral
Tramontana (2015)                        Bilateral

Planification

Zangaglia (2009)                   Semimicro e lec tro de
Castelli, (2010)                             --
Fasano (2010)                                --
Castelli et al. [54]                Monopolar bilateral

TABLE 2

Neuropsychological test   k    N     Age    Years PD

Verbal fluency-semantic   4   141   60,56    12,96
Verbal fluency-Phonetic   7   178   60,21    13,51
WSCT                      2   51    60,47    10,97
WSCT-Nelson               5   92    58,72     13,1
Trail Making Test-B       8   161   60,91    12,45
Corsi Span Backward       4   86    59,86    14,56
Digit Span Test           7   246   59,22    13.06
Trail Making Test-A       3   69    61,6      10,8
Stroop                    9   246   65,2     12,18
Planning                  4   98    59,61    13.85

Neuropsychological test              DBS

Verbal fluency-semantic              STN
Verbal fluency-Phonetic              STN
WSCT                                 STN
WSCT-Nelson                          STN
Trail Making Test-B                  STN
Corsi Span Backward                  STN
Digit Span Test                    STN-GPi
Trail Making Test-A                  STN
Stroop                    STN-Cingulate (1)-GPi (1)
Planning                             STN

                                  Heterogeneity

Neuropsychological test     Q      p(Q)    [I.sup.2]

Verbal fluency-semantic
Verbal fluency-Phonetic   19,769   0,032     49,41
WSCT
WSCT-Nelson               34,759   0,021     42,46
Trail Making Test-B        5,26    0,511     0,000
Corsi Span Backward
Digit Span Test           3,088    0,686     0,000
Trail Making Test-A       0,581    0,748     0,000
Stroop                    102,7    0,001     77,6
Planning

Note: k, number of studies; N, number of patients, DBS (deep brain
stimulation); Q, heterogeneity intradomain; p(Q) p value of Q
statistic; I , percent of heterogeneity from difference.

FIGURE 3: Meta-analysis of verbal fluency comparing before and after
DBS surgery. Verbal fluency was separated in phonetic and semantic
parts. STN = subthalamic nucleus; GPi = internal globus pallidus.

Study name                      Subgroup     Statistics for each study
                              within study
                                             Hedges's g   Variance

Rothlind et al., 2015 (STN)     Phonetic       -0.216      0.012
Rothlind et al., 2015 (GPi)     Phonetic       -0.076      0.012
Tramontana et al., 2015         Phonetic       -0.553      0.070
Houvenaghel et al., 2015        Phonetic       -0.585      0.043
Takehiko. Y et al. 2012         Phonetic       -0.302      0.033
Saez-Zea C. et al., 2012        Phonetic       -1.083      0.156
Merola et al. 2011              Phonetic       -0.834      0.063
Le Jeune et al., 2008           Phonetic       0.181       0.069
Daniels et al. 2012             Phonetic       -0.305      0.017
Castelli et al., 2010           Phonetic       -0.206      0.036
Castelli et al. 2007            Phonetic       -0.862      0.068
Rothlind et al., 2015 (STN)     Semantic       -0.216      0.012
Rothlind et al., 2015 (GPi)     Semantic       0.077       0.013
Tramontana et al., 2015         Semantic       -0.231      0.061
Houvenaghel et al., 2015        Semantic       -0.130      0.036
Takehiko. Y et al. 2012         Semantic       -0.651      0.039
Daniels et al. 2012             Semantic       -0.283      0.017
Zangaglia, R., et al. 2009      Semantic       -0.337      0.032
Bergamasco et al 2007           Semantic       -0.117      0.049
Tang et al, 2015 (STN)          Semantic       -0.559      0.041
Tang et al, 2015                Semantic       -0.559      0.041
                                               -0.266      0.001

Study name                    Statistics for each study

                              Standard   Lower    Upper
                               error     error    limit

Rothlind et al., 2015 (STN)    0.110     -0.432   -0.001
Rothlind et al., 2015 (GPi)    0.112     -0.294   0.143
Tramontana et al., 2015        0.264     -1.070   -0.035
Houvenaghel et al., 2015       0.207     -0.991   -0.180
Takehiko. Y et al. 2012        0.182     -0.659   0.055
Saez-Zea C. et al., 2012       0.395     -1.857   -0.310
Merola et al. 2011             0.252     -1.327   -0.340
Le Jeune et al., 2008          0.262     -0.333   0.694
Daniels et al. 2012            0.130     -0.560   -0.049
Castelli et al., 2010          0.189     -0.576   0.164
Castelli et al. 2007           0.260     -1.372   -0.351
Rothlind et al., 2015 (STN)    0.110     -0.432   -0.001
Rothlind et al., 2015 (GPi)    0.114     -0.146   0.300
Tramontana et al., 2015        0.248     -0.717   0.255
Houvenaghel et al., 2015       0.191     -0.505   0.244
Takehiko. Y et al. 2012        0.197     -1.036   -0.265
Daniels et al. 2012            0.130     -0.538   -0.029
Zangaglia, R., et al. 2009     0.178     -0.685   0.011
Bergamasco et al 2007          0.221     -0.550   0.315
Tang et al, 2015 (STN)         0.202     -0.954   -0.164
Tang et al, 2015               0.202     -0.954   -0.164
                               0.036     -0.337   -0.195

Study name                    Statistics for each study

                              Z value   p value

Rothlind et al., 2015 (STN)   -1.966     0.049
Rothlind et al., 2015 (GPi)   -0.677     0.499
Tramontana et al., 2015       -2.092     0.036
Houvenaghel et al., 2015      -2.831     0.005
Takehiko. Y et al. 2012       -1.660     0.097
Saez-Zea C. et al., 2012      -2.744     0.006
Merola et al. 2011            -3.309     0.001
Le Jeune et al., 2008          0.689     0.491
Daniels et al. 2012           -2.336     0.019
Castelli et al., 2010         -1.091     0.275
Castelli et al. 2007          -3.309     0.001
Rothlind et al., 2015 (STN)   -1.966     0.049
Rothlind et al., 2015 (GPi)    0.677     0.499
Tramontana et al., 2015       -0.933     0.351
Houvenaghel et al., 2015      -0.681     0.496
Takehiko. Y et al. 2012       -3.309     0.001
Daniels et al. 2012           -2.179     0.029
Zangaglia, R., et al. 2009    -1.897     0.058
Bergamasco et al 2007         -0.532     0.595
Tang et al, 2015 (STN)        -2.771     0.006
Tang et al, 2015              -2.771     0.006
                              -7.328     0.000

FIGURE 5: Meta-analysis of WSCT comparing before and after DBS
surgery. The Wisconsin Short Card Test had three versions. Version
one: MWCST = modified WCST; version two: WSCT; and version three:
WSCT Nelson version.

Study name                                      Statistics for each
                                   Subgroup              study

                                 within study   Hedges's g   Standard
                                                              error

Fasano et al., 2010, CAT            MWCST         -0.148      0.216
Le Jeune et al., 2010, CAT          MWCST         0.148       0.216
Fasano et al., 2010, E              MWCST         -0.148      0.216
Le Jeune et al., 2010, E            MWCST         0.614       0.236
Fasano et al., 2010, P              MWCST         0.148       0.216
Le Jeune et al., 2010, P            MWCST         0.614       0.236
Houvenaghel et al., 2015, CAT       MWCST         0.130       0.191
Houvenaghel et al., 2015, E         MWCST         0.130       0.191
Zangaglia, R., et al. 2009, E        WSCT         0.118       0.173
Williams et al., 2011, E             WSCT         -0.359      0.227
Fraraccio et al., 2008, EP           WSCT         0.238       0.256
Rothlind et al., 2015 (GPi) E        WSCT         0.075       0.110
Rothlind et al., 2015 (sTN), P       WSCT         0.076       0.112
Tramontana et al., 2015, E           WSCT         0.131       0.245
Tramontana et al., 2015, EP          WSCT         -0.524      0.262
Fraraccio et al., 2008, CAT          WSCT         0.169       0.254
Fraraccio et al., 2008, NPE          WSCT         -0.403      0.263
Castelli et al. 2007, CAT        WSCT Nelson      -0.151      0.221
Castelli et al., 2010, CAT       WSCT Nelson      0.128       0.188
Le Jeune et al., 2010, CAT       WSCT Nelson      -0.181      0.262
Castelli et al. 2007, E          WSCT Nelson      -0.151      0.221
Castelli et al., 2010, E         WSCT Nelson      0.128       0.188
Le Jeune et al., 2010, E         WSCT Nelson      0.793       0.303
Castelli et al. 2007, P          WSCT Nelson      -0.151      0.221
Castelli et al., 2010, P         WSCT Nelson      0.128       0.188
Le Jeune et al., 2010, P         WSCT Nelson      0.793       0.303
Williams et al., 2011, P         WSCT Nelson      -0.359      0.227
                                                  0.064       0.053

Study name                       Statistics for each study

                                 Variance   Lower    Upper
                                            limit    limit

Fasano et al., 2010, CAT          0.047     -0.571   0.276
Le Jeune et al., 2010, CAT        0.047     -0.276   0.571
Fasano et al., 2010, E            0.047     -0.571   0.276
Le Jeune et al., 2010, E          0.056     0.152    1.076
Fasano et al., 2010, P            0.047     -0.276   0.571
Le Jeune et al., 2010, P          0.056     0.152    1.076
Houvenaghel et al., 2015, CAT     0.036     -0.244   0.505
Houvenaghel et al., 2015, E       0.036     -0.244   0.505
Zangaglia, R., et al. 2009, E     0.030     -0.222   0.457
Williams et al., 2011, E          0.052     -0.804   0.087
Fraraccio et al., 2008, EP        0.065     -0.263   0.738
Rothlind et al., 2015 (GPi) E     0.012     -0.141   0.291
Rothlind et al., 2015 (sTN), P    0.012     -0.143   0.294
Tramontana et al., 2015, E        0.060     -0.350   0.612
Tramontana et al., 2015, EP       0.069     -1.037   -0.010
Fraraccio et al., 2008, CAT       0.064     -0.328   0.666
Fraraccio et al., 2008, NPE       0.069     -0.918   0.112
Castelli et al. 2007, CAT         0.049     -0.585   0.282
Castelli et al., 2010, CAT        0.035     -0.240   0.496
Le Jeune et al., 2010, CAT        0.069     -0.694   0.333
Castelli et al. 2007, E           0.049     -0.585   0.282
Castelli et al., 2010, E          0.035     -0.240   0.496
Le Jeune et al., 2010, E          0.092     0.200    1.386
Castelli et al. 2007, P           0.049     -0.585   0.282
Castelli et al., 2010, P          0.035     -0.240   0.496
Le Jeune et al., 2010, P          0.092     0.200    1.386
Williams et al., 2011, P          0.052     -0.804   0.087
                                  0.003     -0.040   0.167

Study name                       Statistics for each study

                                 Z value   p value

Fasano et al., 2010, CAT         -0.684     0.494
Le Jeune et al., 2010, CAT        0.684     0.494
Fasano et al., 2010, E           -0.684     0.494
Le Jeune et al., 2010, E          2.607     0.009
Fasano et al., 2010, P            0.684     0.494
Le Jeune et al., 2010, P          2.607     0.009
Houvenaghel et al., 2015, CAT     0.681     0.496
Houvenaghel et al., 2015, E       0.681     0.496
Zangaglia, R., et al. 2009, E     0.680     0.496
Williams et al., 2011, E         -1.578     0.115
Fraraccio et al., 2008, EP        0.930     0.352
Rothlind et al., 2015 (GPi) E     0.677     0.499
Rothlind et al., 2015 (sTN), P    0.677     0.499
Tramontana et al., 2015, E        0.534     0.593
Tramontana et al., 2015, EP      -1.997     0.046
Fraraccio et al., 2008, CAT       0.667     0.505
Fraraccio et al., 2008, NPE      -1.534     0.125
Castelli et al. 2007, CAT        -0.684     0.494
Castelli et al., 2010, CAT        0.681     0.496
Le Jeune et al., 2010, CAT       -0.689     0.491
Castelli et al. 2007, E          -0.684     0.494
Castelli et al., 2010, E          0.681     0.496
Le Jeune et al., 2010, E          2.620     0.009
Castelli et al. 2007, P          -0.684     0.494
Castelli et al., 2010, P          0.681     0.496
Le Jeune et al., 2010, P          2.620     0.009
Williams et al., 2011, P         -1.578     0.115
                                  1.203     0.229

FIGURE 7: Meta-analysis of TMT-A comparing before and after DBS
surgery.

Study name                              Statistics for each study

                                   Subgroup                  Standard
                                 within study   Hedges's g    error

Yamanaka et al., 2012               TMT-A         -0.121      0.179
Williams et al., 2011               TMT-A         0.240       0.223
Smeding et al., 2005 (seconds)      TMT-A         -0.121      0.216
Rothlind et al., 2015 (STN)         TMr-A         -0.073      0.108
Rothlind et al., 2015 (GPi)         TMT-A         0.076       0.112
Houvenaghel et al., 2015            TMT-A         -0.130      0.191
                                                  -0.020      0.061

Study name                       Statistics for each study

                                 Variance   Lower limit   Upper limit

Yamanaka et al., 2012             0.032       -0.471         0.228
Williams et al., 2011             0.050       -0.198         0.677
Smeding et al., 2005 (seconds)    0.046       -0.543         0.302
Rothlind et al., 2015 (STN)       0.012       -0.285         0.139
Rothlind et al., 2015 (GPi)       0.012       -0.143         0.294
Houvenaghel et al., 2015          0.036       -0.505         0.244
                                  0.004       -0.140         0.100

Study name                       Statistics for each study

                                 Z value   p value

Yamanaka et al., 2012            -0.680     0.496
Williams et al., 2011             1.074     0.283
Smeding et al., 2005 (seconds)   -0.561     0.575
Rothlind et al., 2015 (STN)      -0.677     0.499
Rothlind et al., 2015 (GPi)       0.677     0.499
Houvenaghel et al., 2015         -0.681     0.496
                                 -0.328     0.743

FIGURE 9: Meta-analysis of TMT-B comparing before and after DBS
surgery.

Study name                         Subgroup     Statistics for each
                                 within study            study

                                                             Standard
                                                Hedges's g    error

Castelli et al., 2010               TMT-B         0.099       0.187
Yamanaka et al., 2012               TMT-B         -0.121      0.179
Merola et al., 2011                 TMT-B         0.204       0.217
Williams et al., 2011               TMT-B         0.211       0.222
Castelli et al., 2007               TMT-B         0.151       0.221
Smeding et al., 2005 (seconds)      TMT-B         -0.052      0.215
Smeding et al., 2005 (errors)       TMT-B         -0.412      0.224
Rothlind et al., 2015 (GPi)         TMT-B         0.076       0.112
Rothlind et al., 2015 (STN)         TMT-B         0.075       0.110
Houvenaghel et al., 2015            TMT-B         0.130       0.191
                                                  0.049       0.053

Study name                       Statistics for each study

                                 Variance   Lower limit   Upper limit

Castelli et al., 2010             0.035       -0.268         0.466
Yamanaka et al., 2012             0.032       -0.471         0.228
Merola et al., 2011               0.047       -0.222         0.629
Williams et al., 2011             0.049       -0.225         0.647
Castelli et al., 2007             0.049       -0.282         0.585
Smeding et al., 2005 (seconds)    0.046       -0.473         0.369
Smeding et al., 2005 (errors)     0.050       -0.852         0.028
Rothlind et al., 2015 (GPi)       0.012       -0.143         0.294
Rothlind et al., 2015 (STN)       0.012       -0.141         0.291
Houvenaghel et al., 2015          0.036       -0.244         0.505
                                  0.003       -0.056         0.153

Study name                       Statistics for each study

                                 Z value   p value

Castelli et al., 2010             0.530     0.596
Yamanaka et al., 2012            -0.680     0.496
Merola et al., 2011               0.938     0.348
Williams et al., 2011             0.948     0.343
Castelli et al., 2007             0.684     0.494
Smeding et al., 2005 (seconds)   -0.244     0.808
Smeding et al., 2005 (errors)    -1.837     0.066
Rothlind et al., 2015 (GPi)       0.677     0.499
Rothlind et al., 2015 (STN)       0.677     0.499
Houvenaghel et al., 2015          0.681     0.496
                                  0.912     0.362

FIGURE 11: Meta-analysis of TMT-AB comparing before and after DBS
surgery.

Study name                      Subgroup     Statistics for each study
                              within study
                                             Hedges's g   Standard
                                                           error

Le Jeune et al., 2008 (B-A)     TMT-B-A        -0.181      0.262
Yamanaka et al., 2012           TMT-B-A        -0.121      0.179
Le Jeune et al., 2010 (B-A)     TMT-B-A        -0.148      0.216
Welter et al, 2015              TMT-B-A        0.278       0.377
Houvenaghel et al., 2015        TMT-B-A        0.130       0.191

Study name                    Statistics for each study

                              Variance   Lower limit   Upper limit

Le Jeune et al., 2008 (B-A)    0.069       -0.694         0.333
Yamanaka et al., 2012          0.032       -0.471         0.228
Le Jeune et al., 2010 (B-A)    0.047       -0.571         0.276
Welter et al, 2015             0.142       -0.460         1.016
Houvenaghel et al., 2015       0.036       -0.244         0.505

Study name                    Statistics for each study

                              Z value   p value

Le Jeune et al., 2008 (B-A)   -0.689     0.491
Yamanaka et al., 2012         -0.680     0.496
Le Jeune et al., 2010 (B-A)   -0.684     0.494
Welter et al, 2015             0.738     0.460
Houvenaghel et al., 2015       0.681     0.496

Figure 13: Meta-analysis of Raven Matrix comparing before
and after DBS surgery.

Study name               Subgroup within study

Fasano et al., 2010      Raven's Progressive Matrices (RPM'47)
Castelli et al, 2007     Raven's Progressive Matrices (RPM'47)
Zangaglia et al., 2009   Raven's Progressive Matrices (RPM'47)
Yamanaka et al., 2012    Raven's Colored Progressive Matrices
Merola et al., 2011      Raven's Colored Progressive Matrices
Castelli et al., 2010    Raven's Colored Progressive Matrices

                         Statistics for each study

Study name               Hedges's g   Standard error

Fasano et al., 2010        -0.028         0.224
Castelli et al, 2007       -0.029         0.229
Zangaglia et al., 2009     0.022          0.177
Yamanaka et al., 2012      0.331          0.188
Merola et al., 2011        0.108          0.224
Castelli et al., 2010      -0.088         0.193
                           0.060          0.083

                         Statistics for each study

Study name               Variance   Lower limit   Upper limit

Fasano et al., 2010       0.050       -0.467         0.410
Castelli et al, 2007      0.053       -0.479         0.421
Zangaglia et al., 2009    0.031       -0.324         0.369
Yamanaka et al., 2012     0.035       -0.036         0.669
Merola et al., 2011       0.050       -0.332         0.547
Castelli et al., 2010     0.037       -0.466         0.290
                          0.007       -0.102         0.222

                         Statistics for each study

Study name               Z value   p value

Fasano et al., 2010      -0.127     0.899
Castelli et al, 2007     -0.127     0.899
Zangaglia et al., 2009    0.127     0.899
Yamanaka et al., 2012     1.766     0.077
Merola et al., 2011       0.480     0.631
Castelli et al., 2010    -0.458     0.647
                          0.726     0.468

The thinking abstract function was evaluated with Raven Matrix
in two versions: Progressive (RPM'47) and Colored.

FIGURE 15: Meta-analysis of DST comparing before and after DBS
surgery.

Study name                      Subgroup     Statistics for each study
                              within study
                                             Hedges's g   Standard
                                                           error

Fasano et al., 2010             Forward        -0.148      0.216
Tang et al, 2015, 12 months     Forward        0.017       0.187
Rothlind et al., 2015 (GPi)     Forward        -0.076      0.112
Rothlind et al., 2015 (STN)     Forward        -0.073      0.108
Yamanaka et al., 2012           Forward        -0.121      0.179
Merola et al. 2011              Forward        0.003       0.215
Williams et al., 2011           Forward        -0.408      0.229
Daniels et al., 2010            Forward        0.073       0.128
Fraraccio et al., 2008          Forward        0.104       0.245
Will et al, 2008                Forward        0.073       0.128
Rothlind et al., 2007           Forward        -0.408      0.255
Tang et al, 2015, 6 months      Forward        -0.017      0.187
Fasano et al., 2010             Backward       -0.148      0.216
Yamanaka et al., 2012           Backward       -0.121      0.179
Daniels et al., 2010            Backward       -0.139      0.128
Will et al, 2008                Backward       -0.139      0.128
Rothlind et al., 2007           Backward       0.317       0.251
Tang et al, 2015, 6 months      Backward       -0.017      0.187
Tang et al, 2015, 12 months     Backward       0.256       0.190
Rothlind et al., 2015 (GPi)     Backward       -0.076      0.112
Rothlind et al., 2015 (STN)     Backward       -0.073      0.108
Zangaglia et al., 2009          Backward       0.022       0.172
                                               -0.051      0.033

Study name                    Statistics for each study

                              Variance   Lower limit   Upper limit

Fasano et al., 2010            0.047       -0.571         0.276
Tang et al, 2015, 12 months    0.035       -0.350         0.383
Rothlind et al., 2015 (GPi)    0.012       -0.294         0.143
Rothlind et al., 2015 (STN)    0.012       -0.285         0.139
Yamanaka et al., 2012          0.032       -0.471         0.228
Merola et al. 2011             0.046       -0.418         0.424
Williams et al., 2011          0.053       -0.857         0.042
Daniels et al., 2010           0.016       -0.177         0.323
Fraraccio et al., 2008         0.060       -0.376         0.583
Will et al, 2008               0.016       -0.177         0.323
Rothlind et al., 2007          0.065       -0.908         0.092
Tang et al, 2015, 6 months     0.035       -0.383         0.350
Fasano et al., 2010            0.047       -0.571         0.276
Yamanaka et al., 2012          0.032       -0.471         0.228
Daniels et al., 2010           0.016       -0.390         0.112
Will et al, 2008               0.016       -0.390         0.112
Rothlind et al., 2007          0.063       -0.175         0.809
Tang et al, 2015, 6 months     0.035       -0.383         0.350
Tang et al, 2015, 12 months    0.036       -0.117         0.628
Rothlind et al., 2015 (GPi)    0.012       -0.294         0.143
Rothlind et al., 2015 (STN)    0.012       -0.285         0.139
Zangaglia et al., 2009         0.030       -0.316         0.360
                               0.001       -0.115         0.014

Study name                    Statistics for each study

                              Z value   p value

Fasano et al., 2010           -0.684     0.494
Tang et al, 2015, 12 months    0.089     0.929
Rothlind et al., 2015 (GPi)   -0.677     0.499
Rothlind et al., 2015 (STN)   -0.677     0.499
Yamanaka et al., 2012         -0.680     0.496
Merola et al. 2011             0.014     0.989
Williams et al., 2011         -1.777     0.076
Daniels et al., 2010           0.570     0.568
Fraraccio et al., 2008         0.423     0.672
Will et al, 2008               0.570     0.568
Rothlind et al., 2007         -1.598     0.110
Tang et al, 2015, 6 months    -0.089     0.929
Fasano et al., 2010           -0.684     0.494
Yamanaka et al., 2012         -0.680     0.496
Daniels et al., 2010          -1.085     0.278
Will et al, 2008              -1.085     0.278
Rothlind et al., 2007          1.264     0.206
Tang et al, 2015, 6 months    -0.089     0.929
Tang et al, 2015, 12 months    1.345     0.179
Rothlind et al., 2015 (GPi)   -0.677     0.499
Rothlind et al., 2015 (STN)   -0.677     0.499
Zangaglia et al., 2009         0.127     0.899
                              -1.533     0.125

FIGURE 17: Meta-analysis of Stroop Test comparing before and after
DBS surgery.

                                 Statistics for each study

Study name                                    Standard
                                 Hedges's g    error     Variance

Le Jeune et al., 2008              -0.793      0.303      0.092

Rothlind et al., 2007 (Stroop      -0.448      0.257      0.091
word)

Rothlind et al., 2007 (Stroop      -0.566      0.265      0.093
colour)

Rothlind et al., 2007 (Stroop      -0.537      0.263      0.013
colour-word)

Williams et al., 2011 (Stroop      -0.166      0.221      0.094
word)

Williams et al., 2011 (Stroop      -0.423      0.230      0.013
colour-word)

Le Jeune et al., 2010              -0.027      0.215      0.017

Fraraccio et al., 2008 (colour     -0.516      0.270      0.018
naming (# in 45 s))

Fraraccio et al., 2008 (word       -0.878      0.301      0.017
reading (# in 45 s))

Fraraccio et al., 2008             -0.915      0.305       0.07
(interference index (c/w) (#
in 45 s)

Rothlind et al., 2015 (GPi),       -0.077      0.114      0.066
word reading

Rothlind et al., 2015 (STN),       -0.076      0.112      0.069
word reading

Rothlind et al., 2015 (GPi),       -0.077      0.114      0.049
colour naming

Rothlind et al., 2015 (STN),       -0.223      0.114      0.053
colour naming

Rothlind et al., 2015 (GPi),       -0.077      0.114      0.046
colour word

Tramontana et al., 2015            -0.060      0.244      0.073
(palabra)

Tramontana et al., 2015            -0.016      0.244      0.013
(colour)

Tramontana et al., 2015            -1.011      0.306      0.013
(colour-palabra)

Rothlind et al., 2015 (STN),       -0.223      0.114      0.013
colour word

Houvenaghel et al., 2015,          -0.130      0.191      0.013
colour

Houvenaghel et al., 2015, word     -0.130      0.191       0.06

Houvenaghel et al., 2015,          -0.130      0.191       0.06
colour-word

Houvenaghel et al., 2015,          -0.130      0.191      0.036
interference

Smeding et al., 2005 (Stroop       -0.105      0.215      0.036
word seconds)

Smeding et al., 2005 (Stroop       0.314       0.220      0.036
colour seconds)

Smeding et al., 2005 (Stroop       -0.124      0.216      0.036
colour word seconds)

Smeding et al., 2005 (Stroop       -0.272      0.219      0.046
colour word errors)

Daniels et al., 2010 (Stroop       -0.235      0.129      0.049
word seconds)

Daniels et al., 2010 (Stroop       -0.255      0.130      0.046
colour seconds)

Daniels et al., 2010 (Stroop       -0.441      0.134      0.048
interference condition/word
reading)

Daniels et al., 2010 (Stroop       -0.305      0.130      0.017
interference condition/colour
naming)

Wills et al., 2008 (Stroop 1       -0.235      0.129      0.017
word reading time in black,
seconds)

Wills et al., 2008 (Stroop 1       0.255       0.130      0.017
word reading time in black,
error rates)

Wills et al., 2008 (Stroop 2       -0.255      0.130      0.017
word reading time naming
colour dots for simple colour
naming)

Wills et al., 2008 (Stroop 2       0.441       0.134      0.018
naming colour dots for simple
colour naming, error rates)

Wills et al., 2008 (Stroop 3:      -0.441      0.134      0.018
interference condition reading
words, seconds)

Wills et al., 2008 (Stroop 3:      -0.067      0.128      0.017
interference condition reading
words, error rates)

Wills et al., 2008 (Stroop 4       -0.305      0.130      0.016
interference condition,
seconds)

Wills et al., 2008 (Stroop 4       -0.113      0.128      0.034
interference condition, error
rates)

Yamanaka et al., 2012, MST-A       -0.364      0.184      0.036

Yamanaka et al., 2012, MST-B       -0.490      0.189      0.016
                                   -0.211      0.039      0.002

                                       Statistics for each study

Study name                       Lower    Upper
                                 limit    limit   Z value   p value

Le Jeune et al., 2008            ?1.386   -0.200  -2.620     0.009

Rothlind et al., 2007 (Stroop    ?0.952   0.057   -1.739     0.082
word)

Rothlind et al., 2007 (Stroop    ?1.086   -0.047  -2.136     0.033
colour)

Rothlind et al., 2007 (Stroop    ?1.053   -0.022  -2.042     0.041
colour-word)

Williams et al., 2011 (Stroop    ?0.600   0.268   -0.749     0.454
word)

Williams et al., 2011 (Stroop    ?0.874   0.028   -1.839     0.066
colour-word)

Le Jeune et al., 2010            ?0.448   0.393   -0.127     0.899

Fraraccio et al., 2008 (colour   ?1.045   0.013   -1.912     0.056
naming (# in 45 s))

Fraraccio et al., 2008 (word     ?1.468   -0.287  -2.913     0.004
reading (# in 45 s))

Fraraccio et al., 2008           ?1.514   -0.317  -2.998     0.003
(interference index (c/w) (#
in 45 s)

Rothlind et al., 2015 (GPi),     ?0.300   0.146   -0.677     0.499
word reading

Rothlind et al., 2015 (STN),     ?0.296   0.144   -0.677     0.499
word reading

Rothlind et al., 2015 (GPi),     ?0.300   0.146   -0.677     0.499
colour naming

Rothlind et al., 2015 (STN),     ?0.446   -0.001  -1.966     0.049
colour naming

Rothlind et al., 2015 (GPi),     ?0.300   0.146   -0.677     0.499
colour word

Tramontana et al., 2015          ?0.539   0.419   -0.245     0.807
(palabra)

Tramontana et al., 2015          ?0.494   0.463   -0.064     0.949
(colour)

Tramontana et al., 2015          ?1.611   -0.411  -3.303     0.001
(colour-palabra)

Rothlind et al., 2015 (STN),     ?0.446   -0.001  -1.966     0.049
colour word

Houvenaghel et al., 2015,        ?0.505   0.244   -0.681     0.496
colour

Houvenaghel et al., 2015, word   ?0.505   0.244   -0.681     0.496

Houvenaghel et al., 2015,        ?0.505   0.244   -0.681     0.496
colour-word

Houvenaghel et al., 2015,        ?0.505   0.244   -0.681     0.496
interference

Smeding et al., 2005 (Stroop     ?0.527   0.317   -0.488     0.625
word seconds)

Smeding et al., 2005 (Stroop     ?0.118   0.746    1.425     0.154
colour seconds)

Smeding et al., 2005 (Stroop     ?0.547   0.298   -0.576     0.565
colour word seconds)

Smeding et al., 2005 (Stroop     ?0.701   0.157   -1.244     0.214
colour word errors)

Daniels et al., 2010 (Stroop     ?0.489   0.018   -1.820     0.069
word seconds)

Daniels et al., 2010 (Stroop     ?0.509   -0.001  -1.968     0.049
colour seconds)

Daniels et al., 2010 (Stroop     ?0.703   -0.179  -3.302     0.001
interference condition/word
reading)

Daniels et al., 2010 (Stroop     ?0.560   -0.049  -2.336     0.019
interference condition/colour
naming)

Wills et al., 2008 (Stroop 1     ?0.489   0.018   -1.820     0.069
word reading time in black,
seconds)

Wills et al., 2008 (Stroop 1     ?0.509   0.509    1.968     0.049
word reading time in black,
error rates)

Wills et al., 2008 (Stroop 2     ?0.703   -0.001  -1.968     0.049
word reading time naming
colour dots for simple colour
naming)

Wills et al., 2008 (Stroop 2     ?0.317   0.703    3.302     0.001
naming colour dots for simple
colour naming, error rates)

Wills et al., 2008 (Stroop 3:    ?0.560   -0.179  -3.302     0.001
interference condition reading
words, seconds)

Wills et al., 2008 (Stroop 3:    ?0.363   0.183   -0.527     0.598
interference condition reading
words, error rates)

Wills et al., 2008 (Stroop 4     ?0.724   -0.049  -2.336     0.019
interference condition,
seconds)

Wills et al., 2008 (Stroop 4     ?0.860   0.138   -0.882     0.378
interference condition, error
rates)

Yamanaka et al., 2012, MST-A     ?0.288   -0.003  -1.977     0.048

Yamanaka et al., 2012, MST-B     0.001    -0.120  -2.597     0.009
                                 0.179    -0.135  -5.406     0.000
COPYRIGHT 2017 COPYRIGHT 2010 SAGE-Hindawi Access to Research
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2017 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Martinez-Martinez, A.M.; Aguilar, O.M.; Acevedo-Triana, C.A.
Publication:Parkinson's Disease
Article Type:Report
Date:Jan 1, 2017
Words:14531
Previous Article:Bridging the Gaps in Patient Education for DBS Surgery in Parkinson's Disease.
Next Article:Colonic Oxidative and Mitochondrial Function in Parkinson's Disease and Idiopathic REM Sleep Behavior Disorder.
Topics:

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters