Morphological and functional types of visual cortical neurons in rabbits during postnatal development.

Abstract

1. Eight types of responses of visual cortical neurons are distinguished in rabbits to flashes, and the representative of each type is identified morphologically. 2. It is shown that primary excitation spreads mainly to nonpyramidal neurons in the middle layers of the visual cortex, whereas inhibition predominates in the initial responses of pyramidal cells. 3. Closest agreement between the intracellular response and the primary EP in laminar recordings is observed with nonpyramidal neurons, and secondary responses of the pyramids correspond to the slow surface-negative potential. 4. In early ontogeny (before the animals are able to see) most neurons give responses that cannot be subdivided into types, with the exception of cells responsible for reception of the afferent flow. 5. The absence of reversal of EP in the depth of the visual cortex at an early age can be explained by immaturity of the nonpyramidal neurons which play an important role in the genesis of visual cortical EPs. 6. Maturation of the function of the afferent stellate cells by the moment of acquisition of vision and of the inhibitory interneurons in the second week of postnatal life leads to increased complexity of the responses of the pyramidal cells and to qualitative changes in the organization of the visual cortex.