Functional organization of the callosal connections of the cat auditory cortex.

In acute experiments on immobilized cats, using a method of topographical recording of homotopic and heterotopic transcallosal responses, the functional organization of the callosal connections of the auditory cortex was investigated. It was established that the homotopic potentials of the primary projection field (AI) have the greatest amplitude, minimal temporal parameters, and the maximal stability of these characteristics as compared with the associative fields of the auditory cortex (AII, AIV, Ep). The heterotropic transcallosal responses in field AI appeared during stimulation of the analogous field, while in field Ep, they were recorded both during stimulation of the analogous field, and of fields AI and AII of the opposite hemisphere. It is hypothesized that the structure of the transcallosal connections of the primary projection field s of the auditory cortex is characterizised by homotopy, whereas in the associative auditory fields the role of heterotopic transcallosal interactions increases. It is possible that such a structure of the transcallosal connections assures a significant role for interhemispheric interactins in the mechanisms of spatial audition.