Ocular dominance in layer IV of the cat's visual cortex and the effects of monocular deprivation.

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Abstract
The relation between the physiological pattern of ocular dominance and the anatomical distribution of geniculocortical afferents serving each eye was studied in layer IV of the primary visual cortex of normal and monocularly deprived cats. One eye was injected with radioactive label. After sufficient time for transneuronal transport, micro-electrode recordings were made and the geniculocortical afferents serving the injected eye were located autoradiographically. In layer IV of normal cats, cells were clustered according to eye preference, and fewer cells were binocularly driven than in other layers. Points of transition between groups of cells dominated by one eye and those dominated by the other were marked with electrolytic lesions. A good correspondence was found between the location of cells dominated by the injected eye and the patches of radioactively labeled geniculocortical afferents. Following prolonged early monocular deprivation, the patches of geniculocortical afferents in layer IV serving the deprived eye were smaller and those serving the non-deprived eye larger than normal. There was a coincidence between the patches of radioactively labeled afferents and the location of cells dominated by the injected eye. The deprived eye dominated a substantial fraction (22%) of cortical cells in the fourth layer. In other cortical layers, only 7% of the cells were dominated by the deprived eye. The thalamocortical projection apparently is physically rearranged as a consequence of monocular deprivation as demonstrated for layer IVc of the monkey''s visual cortex (Hubel, Wiesel and LeVay).