Single cell analysis of sensory interaction in anterior lateral and suprasylvian gyri of the cat cerebral cortex

Abstract

Patterns of neuronal responsiveness to visual, auditory and somatosensory stimuli were studied in association cortex of cats anesthetized with chloralose anesthesia. With all types of stimuli the convergence of subthreshold excitatory activity upon neurons was demonstrated during the passage of current through the recording microelectrode (tip positive). Long-duration (100–300 msec) inhibitory responses were common at these cortical sites and were sometimes followed by a burst of spike activity. This postinhibitory burst discharge apparently was responsible for facilitatory interactions between stimuli at long conditioning-test intervals. Unequal blocking effects between stimuli also were observed during interactions. When peripheral stimuli were employed (light flash, auditory click, and forepaw shock) most cells in anterior lateral gyrus exhibited preferential responsiveness to auditory click stimulation. This preferential responsiveness, however, was dependent upon the types of stimuli employed; when cells were activated by electrical stimulation of optic and auditory nerves and the dorsal column of the spinal cord, equal responses to the stimuli were most prevalent. A comparison of response characteristics in anterior lateral and anterior middle suprasylvian gyri revealed that responses to sensory stimuli were not identical in these two association areas, irrespective of the types of stimuli. The data suggest that association areas have different sources of input and that cellular mechanisms are available in these areas for the interaction of sensory-specific information.