Laminar distribution of geniculo-cortical afferents in visual cortex of the postnatal kitten

Abstract

The intracortical distribution of degenerating processes in immature visual cortex has been examined with light (Fink-Heimer method) and electron microscopy following the production of electrolytic lesions in the lateral geniculate body or perigeniculate regions in kittens ranging in age from 4 days to 2 weeks. In very young kittens (less than 2 weeks of age) degenerating processes were largely confined to superficial layers of cortex (layers I and II). The distribution of degeneration in layer IV was noticeable in older kittens. A close correspondence was observed between light and electron microscopic findings in respect to the distribution of degeneration. The data obtained suggest that the development of geniculo-cortical afferents occurs as a two-stage temporally overlapping process consisting of an early phase of axodendritic input to superficial cortical elements and a later developing input to layer IV. These morphological observations are discussed in relation to postnatal alterations in the electrographic characteristics of visual evoked responses in the kitten.