THE IMMEDIATE EFFECT OF SPINAL TRANSECTION ON THE CROSSED EXTENSION REFLEX

Abstract

Transection of the spinal cord above the lumbar enlargement in the decerebrate cat caused immediate changes in the crossed extension reflex, i.e.: (a) greatly increased muscular response to a single afferent volley; (b) abolition of after-discharge and summation of central effects of successive volleys; (c) decline in the size of individual responses of a series at frequencies which before transection caused cumulative contractile tension. Interruption of inhibitory impulses from higher centers (offered to explain like changes in flexion reflex) cannot explain these changes, for these centers are excitatory to the extensor center. The mechanism of the change appears to be fundamentally the same in both reflexes.