REVERSAL IN THE CROSSED EXTENSION REFLEX IN DECEREBRATE, DECAPITATE AND SPINAL CATS

Abstract

HContralateral reflexes have been examined in the muscles acting at the ankle joint, in 14 decerebrate, 4 decapitate and 19 spinal cats. The state of neural balance in the spinal centers is a very important factor in determining the type of reflexes present. Reversals have been seen in a great many of these preparations. Weak stimuli usually elicit extension reflexes and stronger ones tend to bring in flexion. Changes in reflex type were found on changing the nerve stimulated. The saphenous nerve gave crossed extension in the anemic decerebrate preparations while the tibial at the ankle and the femoral at times showed flexor involvement either as contraction, alternate contraction or pure crossed flexion. Similar reversals were seen in decapitate and spinal animals but in the latter the tibial sometimes gave extension responses and the saphenous flexion. In the decerebrate preparations, rapid faradic stimulation sometimes showed flexor participation in the response while slower stimulation of the same strength gave crossed extension alone. This frequency reversal was not seen in decapitate and only once in spinal animals.