Sensory Map Plasticity

Using a mapping technique with an array of microelectrodes over the cortical surface of monkeys, Merzenich and colleagues conducted a series of experiments that demonstrate the mutability of so-matosensory representations.388 Following the amputation of a digit in adult monkeys, the sensory representation of adjacent digits in cortical areas 3b and 1 enlarged topographically by approximately 1 mm to occupy the territory that had been filled by the sensory neurons associated with the lost...

Primary Sensory Cortex

The primary sensory cortex SI, which includes BA 3a, 3b, 1, and 2, receives thalamically relayed cutaneous and proprioceptive inputs. The divisions of these regions are not always outlined quite the way Brodmann mapped them.86 Other anatomic and functional neu-roimaging studies find additional subregions and somewhat different borders, which may acount for variations in the localization of activations between subjects during functional imaging studies. For example, although BA 2 is regularly...

Central Pattern Generation

All mammals that have been studied, including a nonhuman primate,156 possess a lumbar rhythm-generating network that can conduct reciprocal stepping movements.124 This self-oscillating interneuronal network is found in a section of the lumbar spinal cord after it is severed from all descending and dorsal root inputs, leaving only the isolated cord segment and its ventral roots (Fig. 1-5B). The isolated lumbar spinal cord, after stimulation by drugs such as clonidine or dihydroxyphenylalanine,...

Primary Motor Cortex and Hand Function

What aspects of hand movement are encoded by Ml The Ml has been described as a computational map for sensorimotor transformations, rather than a map of muscles or of particular movement patterns.l9 Its overlapping organization contributes to the control of the complex muscle synergies needed for fine coordination and forceful contractions.35 After le-sioning Ml in a monkey, the upper extremity is initially quite impaired. The hand can be retrained, however, to perform simple movements and...

Parietal Sensory Cortex

BA 5 and 7, separated by the intraparietal sul-cus from BA 39 (corresponding broadly to the angular gyrus), and BA 40 (approximately the supramarginal gyrus) complete the parietal sensory region. The cell types and neurotrans-mitter receptor densities of the cortical layers vary within areas of the parietal cortex. BA 5 and 7 can be conceived as parasensory association areas. Along with the visual and auditory cortices, these two areas process sensory information and, with their hippocampal...

Organization of the Primary Motor Cortex

The primary motor cortex has an overall soma-totopic organization for the major parts of the body, not unlike what Penfield and Rasmussen found in their cortical stimulation studies in the 1940s.21 In addition, separable islands of cortical motoneurons intermingle to create a more complex map for movement than the neatly portrayed traditional cartoons of a human ho-munculus.22 For example, M1 has separate clusters of output neurons that facilitate the activity of a single spinal motoneuron....

Network Emotional Regulatory Network Spatial Awareness Network Language Network Summary

The central (CNS) and peripheral (PNS) nervous system matrix is a rich resource for learning and for retraining. This chapter begins with the structural framework of interconnected neural components that contribute to motor control for walking, reaching, and grasping, and to cognition and mood. I then review what we know about cellular mechanisms that may be manipulated by physical, cognitive, and pharmacologic therapies to lessen impairments and disabilities. These...

Spinal Reflexes

Many theories of physical therapy focus on the use of brain stem and spinal reflexes as a way to retrain voluntary movement and affect hy-potonicity and hypertonicity. Tonic and phasic stimuli can modify the excitability of spinal motor pools, postural reflexes, and muscle cocontractions. The response to muscle stretch during passive movement, postural adjustment, and voluntary movement is not inflexible. Moment to moment adjustments in reflexes have been partly accounted for by a variety of...