LACK OF PROJECTIONS FROM MEDIAL GENICULATE-BODY TO SUPRASYLVIAN CORTEX IN CAT - A STUDY WITH HORSERADISH-PEROXIDASE

Because both electrophysiological and behavioral methods have implicat ed the suprasylvian cortex of cat in audition, its afferents were stud ied using retrograde transport of horseradish peroxidase. The bulk-fil ling method was used to maximize the likelihood that virtually all aff erents to the area would be labeled. Despite the vivid retrograde labe ling of many thalamic cells with this procedure, no direct auditory pr ojections to the suprasylvian cortex could be found in the thalamus (i .e. in medial geniculate body or in the dorsolateral part of the poste rior nucleus). Furthermore, very few cells were labeled in the primary auditory cortex of the nearby ectosylvian gyrus. The source of affere nts to the suprasylvian cortex originate mostly from the pulvinar-late ral posterior complex and to a lesser extent from ventral lateral and ventral anterior nuclei of the thalamus.