[Connection of the auditory cortex secondary zones with the auditory subcortical cerebral centers in the cat]

As it has been demonstrated microscopically, the corticofugal fibers in the AII and Ep zones of the auditory cortex in all the auditory subcortical centers (medial geniculate body, posterior colliculi of the tectum mesencephali and the superior olive nuclei) terminate by means of single axodendritic synapses, having an asymmetrically active zone, and mixed (by their form) synaptic vesicles. Small and middle dendrites make their postsynaptic part. A comparison has been carried out on distribution and form of synapses, completing the projection fibers from the zone of the primary acoustic responses (AI) and of the primary acoustic zone (AIV). Basing on the morphological data, concerning distribution and form of the synaptic terminals, a suggestion is made that physiological influence of each acoustic cortex zone is different for the medial geniculate body and posterior colliculi of the tectum mesencephali, but it is unitypical for the superior olive level.