The nature of transcallosal responses in the parietal cortex of kittens.

The nature of transcallosal responses in the parietal cortex was studied in experiments with kittens age 2 to 18 days, immobilized with Diplacin. The recorded potentials were represented by a positive-negative complex that was often accompanied by a latent negative oscillation. It was established that the earlier positive-negative oscillation was callosal in nature, and the later, extracallosal. As the kittens developed, we noted that currents responsible for the appearance of early and late negative oscillations converged in time. The results of layer-by-layer analysis of transcallosal responses showed that as the kittens developed, discharge of the surface positive component shifted from layer V to layer III, and discharge of the surface-negative remained at the II-III layer level. The late negative component was recorded only to the level of layers III-IV, having a discharge in layers I-II. Thus, the interhemispheric interrelations in the parietal cortex of kittens are realized by both callosal and extracallosal systems, and an increase in the degree of their interaction can be observed as the kittens grow.