Recent studies have revealed that the details of somatosensory cortical maps are dynamically maintained and are alterable by experience in adult primates. Substantial changes in map topography in receptive sizes are seen consequent from peripheral nerve transection, amputation, or differential tactile stimulation of restricted skin surfaces. Cortical maps also reorganize after induction of restricted cortical lesions. With that reorganization, skin surfaces formerly represented within lesions come to be represented in the cortex surrounding them. In this renewal period, studies will be directed toward a further definition of the """"""""rules"""""""" of cortical map alteration with experience. Behavioral and chronic physiological studies are designed to determine what features of input are actually correlated in the control of the input """"""""selection"""""""" underlying map dynamism and territorial competition. They shall also reveal distance limits for reorganization for different cortical fields suspected on anatomical grounds to have greatly different capacities for use-dependent modifications. They shall further test the hypothesis that map changes are a consequence of changes in synaptic effectiveness and not a consequence of sprouting or movements of terminal arbors; shall determine whether inputs from different receptors can dominate the driving of the same neuronal population at different times; shall determine whether input """"""""selection"""""""" by middle-layer cortical neurons is by groups of neurons or occurs cell by cell. Correlative studies shall be conducted in Al in the cat and in area 4 in the owl monkey, to determine whether they have the same dynamic properties. In parallel more practical experiments will be directed toward evaluating the time course of observed physiological """"""""recover"""""""" from stroke; toward defining cortical distance limits for recovery in fields in what is expected to be differences on anatomical grounds; and toward evaluating the consequences for the rate and the quality of recovery of heavy passive and active differential use of the skin surfaces formerly represented in the cortical zone of the infarct. We shall also determine whether the time courses of cortical map alterations by experience can be modulated by factors effecting """"""""state-dependent"""""""" learning, and shall attempt to determine whether maps can be pharmaceutically stabilized, or restabilized or hyperstabilized. It is believed that these studies might provide insight into possible origins or some forms of mental illness.
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