On the Postnatal Development of Postural Mechanisms as Revealed by Electromyography and Myography in Decerebrate Kittens

Abstract

Abstract The present paper is one in a series of studies on the postnatal development of postural reflex activity in the kitten. Its aim is to investigate the reactions to decerebration and additional ablation of the anterior lobe of the cerebellum in these animals from birth until they are able to walk and stand. An attempt was made by electromyography and myography to trace the mechanisms behind the different reactions. It is shown that alpha rigidity is present in the newborn kitten while gamma rigidity develops later, appearing first in the forelimbs around a fortnight after birth and in the hindlimbs after three weeks. The missing gamma rigidity in the newborn animal is readily explained by the observation that no tonic stretch reflexes, as revealed by electromyography can be obtained from the muscles concerned with decerebrate rigidity. The tonic stretch reflex develops in a proximo‐distal direction in the limbs as revealed by electromyography and is earlier obtained in the alpha than the gamma animal and earlier in the forelimbs than the hindlimbs. This development thus precedes the gamma rigidity which in its development closely follows that of the animal's ability to use its limbs for walking and standing. It also runs in a cranio‐caudal direction.