OBSERVATIONS ON THE RÔLE OF THE CEREBRAL CORTEX IN THE CONTROL OF THE POSTURAL REFLEX

Abstract

This is a report on the electrical exploration of the cat''s cortex followed by an analysis of the influence of such areas, motor and silent, on the locomotor and postural mechanisms. Both acute and chronic experiments were made. Under ether anesthesia responses were elicited from the lateral portion of the area frontalis agranularis, the anterior sigmoid gyrus and the posterior sigmoid gyrus. Removal of these areas resulted only in a transient weakness which disappeared after 48 hrs. The anterior part of the area frontalis agranularis and the gyrus proreus are referred to as the "frontal lobe." This area was silent and its removal gave no motor weakness. After such removal, however, postural and tonic abnormalities could be demonstrated in the contralateral extremities. At first the legs tended to take positions of extreme extension. Later walking was more normal but delicate movements were impossible. The contralateral hind-legs offered strong resistance to passive flexion. The threshold of sensitivity of the foot-pad was greatly increased. On suspension by neck and tail hyperextension of both fore- and hind-leg on the opposite side was observed. Hyperextension was not noted in controls nor in animals with only the motor cortex removed. Since it persisted for 3 mos. it did not appear due to irritation. The extensor hypertonus is interpreted by the author as a release phenomenon following removal of a specific area of the cerebral cortex. The influence normally arising in this area appears to inhibit extensor tonus in the crossed extremities.