The Sensory Cortex of the Chimpanzee. ∗

Abstract

The location, extent and subdivision of the sensory cortex is not known exactly in any species higher than the macaque.

By local cortical strychninization and clinical observation of the animal the location, extent and subdivision of the macaque's sensory cortex was mapped in 1924. 1 By local cortical strychninization and recording of the electrical activity of the leg, arm and face sensory thalamic nuclei, which had been diagnosed physiologically, 2 the original findings were confirmed. 3 Finally, by local strychninization of the cortex this time combined with recording of the typical and typically distributed changes in the electrical activity of the cortex itself (strychnine-spikes) the functional organization of the macaque's sensory cortex was delineated in detail. 4 , 5

This functional organization is so characteristic that it should be recognizable in higher species, such as the chimpanzee, even if details there should prove to be different.

The methods initially used in the macaque would be dangerous with an animal as strong as an anthropoid ape. The sensory thalamic nuclei have not as yet been diagnosed physiologically in the anthropoid and to do it would be equally dangerous. We have, therefore, employed the third procedure, that of local cortical strychninization combined with the recording of the electrical activity of the cortex itself; this can be done in the fully anesthetized animal. When this combination of methods is utilized to study the functional organization of the chimpanzee's cortex it discloses a large region the functional organization of which is comparable to that of the sensory cortex of the macaque. The obvious inference is that the region so disclosed is sensory.

Thus far 4 chimpanzees' brains have been so investigated with essentially similar results.