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...

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,...

Representational Plasticity

Cortical sensory and motor neurons are not permanently fixed in the way they subserve sensing and movement. On the contrary, these neurons quickly adapt to changing demands as new sensory and motor associations are experienced. In the adult and developing animal (see Experimental Case Studies 1-3 and 1-4) and in humans (see Chapter 3), the topographical maps of sensory and motor neuronal representations are capable of rapid and long-term physiologic and structural reorganiza-tion.33,218,219...

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...

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....

Hand Functions

Rudimentary synergistic movements such as opening and closing the hand persist after a pyramidectomy, probably through the activity of the descending rubrospinal, vestibulospinal, and reticulospinal systems.133 These descending pathways mediate skilled forelimb movements, especially movements related to feeding.134 The rubrospinal tract provides a potential path for independent, flexion-biased movements of the elbow and hand.109 The more individuated a movement, the greater the amount of...

Explicit and Implicit Memory Network

Declarative or explicit memory refers to what can be recalled consciously and reported. This form of memory includes episodic memories, which are personal experiences, images and everyday events with their rich contexts and recreation over time, and semantic memories, which refer to the recall of factual knowledge about the world and general information about our surrounds. Declarative memory stands in contrast to implicit or procedural memory, which cannot be overtly reported, such as how one...

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...

Working Memory and Executive Function Network

A critical cognitive process during rehabilitation requires patients to bring information to mind, hold it, and process these mental representations. The prefrontal cortex includes the machinery for online information processing for thought, for comprehension, and for carrying out intentions. Remembering often requires planning and a strategy. Tests of strategic memory, such as the free recall of words, the temporal order of a list of items, and judgments about how often an item has been seen,...