Reorganization of Projection from the Sensory Cortex to the Motor Cortex Following Deprivation of Thalamocortical Projection
Recovery of function following partial destruction of the central nervous system and its neuronal mechanism has been an intriguing question among neurologists and neurophysiologists. It has long been wondered whether the functional recovery is accomplished by anatomical reorganization in the central nervous system or by compensation of the function by the remaining systems Ramon y Cajal  transected the spinal cord of young cats and dogs and reported that a large number of the severed intraspinal fibers sprouted new processes with cones of growth similar to those observed in the peripheral nerves. However, after several weeks these sprouting fibers disappeared, and he concluded that the processes of regeneration were followed by atrophy and absorption. Recent progress in anatomical and physiological techniques, however, has made it possible to reexamine the genesis of the functional recovery. Raisman and Field , using the electron microscope, demonstrated that elimination of one input to the septal nucleus is substituted by new synapses which were formed by the sprouting of the remaining fibers in the rat. Tsukahara et al. , using an intracellular recording technique, demonstrated that the elimination of cerebellar input to the red nucleus resulted in the formation of new synapses by fibers from the cerebral peduncle in the cat. Thus, it seems that at least a part, and probably a major part, of the functional recovery is due to the formation of new synapses by the remaining fibers.
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