Centrifugal control mechanisms

There has been a long-standing descriptive dichotomy between sensorimotor activity of the spinal reflex type, involving only an integrative pattern of connections between sensory and motor nerves within a restricted (low) region of the central nervous system, and discriminative activity, involving ascent of sensory information to a cortical level followed by an appropriate motor output from that level. That this dichotomy is not clear-cut is implicit in experiments with decerebrate and spinal animals. Recent work has shown the existence of widespread centrifugal pathways which interact with sensory inputs at quite low neural levels. Furthermore, interference with these descending pathways has an effect on discrimination quite different from that produced by interference with the classical ascending sensory systems. It is proposed that local sensorimotor configurations play an important role in determining patterns of discriminative behavior, the centrifugal pathways in turn exercising a gating influence on which of the many possible patterns is released in a given set of circumstances.