Sexual dimorphism of the interhemispheric asymmetry dynamics during the processing of the transcallosal signal.

Abstract

The characteristics of the dynamics of the functional interhemispheric asymmetry (FIAs) of the transcallosal influences in male and female rats were compared in this study through an analysis of the amplitude-temporal parameters of the homotopic transcallosal responses (TCR) in the course of their multiple topographical pickup from the dorsolateral surface of the cortex of both hemispheres in the time interval of the realization of the components of the responses. Two principal types of patterns of hemispheric dominance have been distinguished. The first type was described in accordance with the rule of the right-left-right shift of FIAs; the second type was described in accordance with the rule of its left-right-left shift. The changes in the FIAs of the temporal parameters of the positive components and the amplitude parameters of the positive and negative fluctuations were characterized by the identical type of dynamics in rats of both sexes. The dynamics of the FIAs of the temporal parameters of the negative components unfolded in accordance with the first type in the females, but in accordance with the second type in the males. The dominance of the investigated zones of the cortex of the right hemisphere was expressed more markedly in the females at the initial and terminal stages of the processing of transcallosal information. The phases of the dominance of the left hemisphere, by contrast, were identified and detected in a relatively larger territory of the neocortex examined in the males by comparison with the females. The results obtained suggest the relatively greater participation of the cortex of the right hemisphere in the females, but of the left hemisphere in the males during the processing of a transcallosal signal.