A method to study changes in eye-related columns in the visual cortex of kittens during and following early periods of monocular deprivation.

An immunohistochemical method that exploits the rapid light-evoked expression of Fos, the protein product of the immediate early gene, c-fos, to visualize eye-related columns in the visual cortex, has been used to provide preliminary data on the relative innervation of the cortex by the two eyes of monocularly deprived kittens and the speed of the changes that occur afterward during reverse occlusion. In contrast to conventional anatomical techniques, the method allows both cellular resolution and documentation of the dimensions of eye-related columns through the depth of the cortex. In kittens monocularly deprived from near birth, Fos-immunoreactive neurones were observed in oval or circular patches, the size of which decreased as the duration of deprivation was increased from 4 to 6 weeks. Following reverse occlusion at 5 weeks of age, the size of the patches increased rapidly so that after 4 days their area had approximately tripled. In addition to providing possible insights into the anatomical underpinnings of the puzzling behavioural effects that occur following termination of short periods of reverse occlusion, the method can be used to investigate the temporal order of the anatomical effects of monocular deprivation in different cortical layers.