Annual Review of Neuroscience, vol. 20.

Cowan WM, Shooter EM, Stevens CF, Thompson RF, eds. Palo Alto, CA 94303-0139, Annual Reviews Inc, 1997, hardcover, 654 pp, illus, $60.

The articles in this year's Annual Review of Neuroscience fall into three major categories: organization of sensorimotor systems, central neural development and plasticity, and neurochemistry. Although physical therapists will find articles of interest in each section, the section most immediately relevant to clinical research deals with the organization of central neurological systems. Although these articles focus on sensory system organization, they also contain definite applications to sensorimotor behavior.

The article by Wise et al on the premotor and parietal cortex and the article by Andersen et al on the multimodal representation of space in the parietal cortex are particularly valuable to therapists investigating the substrate that underlies the connections between visual, kinesthetic, and vestibular sensory information and motor activity. Andersen et al describe several locations in the parietal lobe that receive multimodal input from sensory receptors in the eyes, neck, auditory system, and vestibular system. This input permits the buildup of convergent maps of space using retinal-, orbital-, head-, and body-centered, coordinate systems. Both of these articles discuss the integration of these complex sensory maps with information relating to movement, using the various coordinate systems for the eyes, the neck, or the upper extremities. Although neither of these articles specifically discusses the issue of balance and postural maintenance, the concepts of coordinate system integration can be applied to questions in these areas. For instance, an area worthy of investigation would be research on how these parietal and premotor regions are involved in patients with closed head injury who have difficulty in performing balance and other basic motor tasks with their eyes open.

The remaining two articles in this cluster concern olfactory discrimination and speech perception. Although these sensory functions are not directly or clinically applicable for most physical therapists, the underlying principles of sensory discrimination can provide useful models for the study of sensory systems involved in motor behavior. Of particular interest is the discussion of the strategies used by the auditory system to "break down" complex speech stimuli into frequency-based components that we learn to recognize as speech phonemes. Fitch et al examine how various species apparently conserve this functional approach to auditory discrimination. They suggest that the unique human capability for speech is built on this conserved mechanism rather than on substrate or function.

In the section on central nervous system development and plasticity, Hatton's article on the hypothalamus contains some particularly interesting observations on the changes in synaptic organization and function that can occur because of shifts in glial-cell spatial relationships. Withdrawal and extension of astrocyte processes over relatively brief time spans allow changes in the expression of gap junction and neurotransmitter synapses without the necessity of neuron process extension and rearrangement. These changes in the hypothalamus are clearly stimulus based and persist as long as the requisite stimuli are present. Although these circumstances might not be the basis for long-term changes in function in sensorimotor systems, they do indicate a potential for functional plasticity that may be of importance in these systems.

Two articles provide models for examining how alterations in the timing of events during early development affect mature functioning and learning potential. Chen and Tonegawa's article on synaptic plasticity directly addresses how various genetic abnormalities affect the potential for motor learning and motor coordination. They emphasize the importance of the timed expression of specific genetic controlling factors during development. Using song production in birds as their model, Bottjer and Arnold also examine the importance of the timing of genetic expression in the development of capability for learning. This article is definitely valuable for researchers interested in possible sexual differentiation of function during development.

Two articles in the section on neural chemistry deal with the chemical bases underlying normal--and possibly pathological--function of motor systems. Fischback and Rosen describe a neuregulin that may be important in regulating the development and location of acetylcholine receptors in muscles as well as neuromuscular junctions. Liu and Edward's study of vesicular transport proteins has implications for the development, and possible prevention and treatment, of Parkinson's disease.

This annual review as usual presents an article that surveys a major historical development in neuroscience. This year, the discussion centers on neural control of pituitary function and the work of Geoffrey Harris in elucidating this field of study.

As is typical of this annual review, all the articles are clearly written and contain extensive analysis of current work in the field. The reference lists are thorough. Line drawings and graphs summarize and highlight important information. Relatively few black-and-white photographs are included, and their quality varies from excellent to unclear.

Elizabeth H Littell, PhD, PT Evaluation and Development Services Albuquerque, NM

Dr Littell is the owner of Evaluation and Development Services, which provides consultation to educational institutions on the development and revision of professional education programs in physical therapy. She is the author of a text on neuroscience.