[Common pathway principle in the organization of callosal connections]

The direct cortical responses and transcallosal potentials were recorded in 170 symmetrical points of the cat motor cortex during the electrical stimulation of one hemisphere. The area of the direct responses was larger than that of transcallosal responses. The latter was concentrated in the center of the motor area, while the direct responses were located in peripheral areas. Thresholds for the direct responses were lower than those for the transcallosal responses. Variation of the strength of the stimulation led to the changes of localization of the EPs in both hemispheres. Callosotomy abolished or decreased the transcallosal potentials and increased or decreased the direct cortical potentials. This suggests the principle of the common pathway for the callosal system activity.