[Asymmetric nature of a focus of maximal activity of transcallosal responses]

In immobilized cats, transcollosal (TCR) and direct cortical responses (DCR) from 170 points of the motor cortex, were recorded. The TCR maximal activity focus (MAF) is shifted in relation to the point symmetrical to stimulation (PSS) in oral--caudal direction. Ablation of the cortex around the stimulating electrode is followed by disappearance of TCR in MAF and of PSS and DCR beyond the ablation limits. Ablation of PSS entails diminishing of TCR in MAF. Transection of the corpus callosum eliminates TCR in MAF and PSS. The MAF shift seems to be due to a relatively strengthened convergence of several excitation flows in PSS, the flows spreading over the callosal fibers and intrahemisphere projections of both hemispheres.