[Some aspects of modular organization of the cat primary visual cortex: cytochrome oxidase activity pattern]

Distribution of enzyme cytochrome oxidase (CO) activity was studied in a continuous series of parasagittal sections of cortical area 17 and frontal sections of dorsal lateral geniculate nucleus (LGNd) in kittens of different age and adult cats. In all the kittens except the newborns, in layer IV of area 17, regular alternating areas of CO activity, exceeding the background activity ("spots"), were detected. During the period between postnatal days 13 and 21 a significant increase of "spots" contrast took place, while between postnatal days 48 and 93 contrast was significantly decreased. This contrast changes coincided with the dynamics of visual system plasticity during ontogenesis. No differences in CO activity were detected between layers A and A1 in LGNd. It is suggested that non-uniform distribution of functional activity of area 17 neurons reflects the development of cortical columns during the critical period of postnatal ontogenesis.