Interhemispheric asymmetry of the interaction of transcallosal and ascending flows of excitation in the visual cortex of the cat.

Interhemispheric interrelationships under conditions of the combination of transcallosal stimulation and monocular photostimulation with varied time intervals have been studied in acute experiments on 20 curarized cats with topographic recording of evoked potentials (EP) from homotypical areas of the visual cortex of both hemispheres. Interhemispheric asymmetry was established in the amplitude-temporal parameters of the visual and transcallosal EP, as well as of the resulting EP in the entire range of lags between the heteromodal stimuli. The asymmetry of the viral EP was greatest in magnitude, the asymmetry of the transcallosal EP was medium in magnitude, and the minimal magnitude was that of the visual EP with photostimulation the contralateral eye. With the combination of transcallosal and visual stimulation, dynamics were found of the magnitude of the resulting EP which reaches a maximum of the magnitude and has a monohemispheric directivity in conditions of the model experiments which correspond to the most natural conditions of the transcallosal interrelationship of the hemispheres. It is hypothesized that the transcallosal interrelationship is an important factor of the formation of the relative specialization of the cerebral hemispheres.