UNIT ANALYSIS OF VISUAL INPUT TO POSTERIOR LIMBIC CORTEX. II. INTRACEREBRAL STIMULI

Publisher Website
Google Scholar
Abstract
The experiments reported here were performed in conjunction with those described in the preceding paper, showing that a brief, intense flash of light activates units in certain areas of the posterior limbic cortex. The purpose was to obtain information about pathways relaying visual impulses to these areas. Experiments were performed on squirrel monkeys anesthetized with chloralose or sitting awake in a special chair. Observations were made on unit responses to electrical stimuli applied to the optic shiasm, lateral geniculate bodies, and striate cortex with bilaterally implanted electrodes. In addition, an attempt was made to learn if limbic afferents of various origin converged on units responding to visual stimulation. Most significant, if anatomically confirmed, was evidence in the waking animal suggestive of direct connections between the ipsilateral geniculate body with limbic cortex near the junction of the posterior hippocampal and lingual gyri and with the presubicular retrosplenial cortex. In anesthetized animals there was also evidence of geniculate influence on units in the hippocampus and in the posterior cingulate gyrus and adjoining parietal cortex. Some units in the latter 2 areas responded both to ipsi- and contralateral stimulation. Unit discharges in all the above areas were also evoked by chiasmal stimulation but usually requiredactivationbya stimulus train. Stimulation of the posteromedial striate cortex evoked unit responses in the ipsi- and contralateral cingulate gyrus. Two units in the hippocampal gyrus and adjoining lingual cortex were unresponsive. Stimulation with electrodes in the anterior cingulate gyrus and in n. lateralis dorsalis activated a few units near the cingulate sulcus that were also responsive to photic stimulation. Three photically driven units in the hippocampal gyrus and one in the prosubiculum also responded, respectively, to stimulation within n. medialis dorsalis and n. ventralis anterior. In conclusion, this study gives further significance to the findings on photic stimulation by indicating a close relationship between the posterior limbic cortex and the geniculostriate system.

This publication has 1 reference indexed in Scilit: