Neuroimaging in rehabilitation: a resource for clinicians.

Advancing rehabilitation research capacity involves understanding the plasticity of neuromuscular tissue, discovering the intervention and dose necessary to adapt the neuromuscular tissue, and verifying that the induced adaptation translates into a functional outcome. (1) An important underlying component of interventions in physical therapy is therapeutic exercise (voluntary or through artificial activation systems). Today, scientific evidence supports the idea that appropriately dosed activity can favorably influence brain plasticity by inducing neuroregenerative, neuroadaptive, and neuroprotective processes. (2) Neuroimaging enables the rehabilitation specialist to quantify the plasticity of the neuromuscular system and determine the activity-based treatment dose that optimizes tissue modeling or remodeling.

The muscular system can be viewed as an extension of the nervous system. It acts as a "transducer" to facilitate the up-regulation of powerful agents--such as brain-derived neurotrophic factor--which can adapt cells within the brain and spinal cord. (3,4) The adaptations induced in the neuromuscular system have powerful implications for the prevention and treatment of aging-related pathologies, Parkinson disease, Alzheimer disease, multiple sclerosis, stroke, head injury, and spinal cord injury. Neuroimaging is and will continue to be an important metric to guide the development of future rehabilitation interventions.

PTJ's Neuroimaging in Rehabilitation series (5-8) is a snapshot that informs readers about contemporary imaging techniques, such as functional magnetic resonance imaging, diffusion tensor imaging, magnetoencephalography, electroencephalography, positron emission tomography, transcranial magnetic stimulation, and muscle magnetic resonance imaging. The authors provide a concise description of the important physics to assist readers in understanding these imaging tools. They also carefully present the underlying physiology contributing to the imaging signal and communicate many of the mechanisms associated with brain and muscle tissue plasticity. Importantly, the authors include "pitfalls and limitations" in the interpretation of many of these imaging techniques. Indeed, they integrate the contemporary literature on neuromuscular plasticity with the "big picture" implications for rehabilitation specialists.

Investigators are using neuroimaging techniques to evaluate the adaptive reorganization that occurs with various types of interventions. This series discusses evidence that supports changes in cortical representation associated with practice and learning new skills in people who are healthy as well as in people with pathology. The relationship between improved motor performance and increased cognitive effort has important implications for the prevention and treatment of dementia associated with aging as well as other neurological diseases. Metabolic changes in muscle, which may co-vary with central nervous system adaptations, are presented in real time and provide a noninvasive state-of-the-art method to assess the plasticity of skeletal muscle. Transcranial magnetic stimulation is an important evaluative tool, but also has emerged as a potential therapy to enhance cortical plasticity and motor function.

This series is special because of the knowledge and expertise of the contributing authors. All of the authors are outstanding scientists, many are educators, and several are experienced clinicians. This level of experience and expertise combines to contribute a unique series of papers that should serve the rehabilitation community well. I congratulate the authors for sharing their expertise and thank the reviewers who provided excellent feedback during the peer-review process. Finally, I would like to acknowledge Andrew Butler, one of the authors, who pioneered the idea for this special issue.

[DOI: 10.2522/ptj.2007.87.6.639]

References

(1) Shields RK. Rehabilitation medicine summit: building research capacity [Invited commentary]. Phys Ther. 2006;86:299-300.

(2) Dishman RK, Berthoud HR, Booth FW, et al. Neurobiology of exercise. Obesity. 2006;14:345-356.

(3) Griesbach GS, Hovda DA, Molteni R, et al. Voluntary exercise following traumatic brain injury: brain derived neurotrophic factor upregulation and recovery of function. Neuroscience. 2004; 125:129-139.

(4) Gomez-Pinilla F, Ying Z, Roy RR, et al. Voluntary exercise induces a BDNF-mediated mechanism that promotes neuroplasticity. J Neruophysiol. 2002;88:2187-2195.

(5) Kimberley TJ, Lewis SM. Understanding neuroimaging. Phys Ther. 2007;87:670-683.

(6) Boyd LA, Vidoni ED, Daly JJ. Answering the call: the influence of neuroimaging and electrophysiological evidence on rehabilitation. Phys Ther 2007;87:684-703.

(7) Segal RL. Use of imaging to assess normal and adaptive muscle function. Phys Ther. 2007;87:704-718.

(8) Butler AJ, Wolf SL Putting the brain on the map: use of transcranial magnetic stimulation to assess and induce cortical plasticity of upper-extremity movement. Phys Ther. 2007;87:719-736.

Richard K Shields, PT, PhD

Editor