Effects of visual deprivation on polyribosome aggregation in visual cortex of the cat

Neurons in the visual cortex of 48 normal and visually deprived kittens and cats were examined electron microscopically for the presence of absence of polyribosomes in their perikaryal cytoplasm. In normal animals at most ages the ribosomes of cortical neurons were aggregated into polysomes, but during the second and third months of life -- a period corresponding approximately to the physiologically defined critical period -- variable numbers of cells were found which contained ribosomes only in the monomeric form. The affected cells were spiny stellate neurons in the fourth layer of the cortex. Even within the critical period, however, cells with dispersed ribosomes were not found in every animal examined.