[Role of several subcortical nuclei in the conduction of visual afferentation during early ontogeny]

Characteristics of EPs in different areas of the visual cortex elicited by stimulation of subcortical nuclei (LGB, posterior thalamic nuclei and superior colliculi) were studied in cat's fetuses during the last 10 days of their antenatal development. It was shown that both in the striate and in accessory visual areas the EPs are negative oscillations with a small initial positivity. Latencies of the EPs to stimulation of the thalamic nuclei make from 18 to 25 msec in different cortical areas and those to the stimulation of the superior colliculi--from 40 to 45 msec. Laminar analysis of EPs elicited in the occipital cortical area by the stimulation of LGB revealed two foci of depolarization; the one with shorter EP latency is localized in the depth of the cortex. The role of the extrageniculate ascending system and of different groups of fibers of the geniculocortical system in the formation of the main EP components in the visual cortex in early ontogenesis is discussed.