Evidence for a loss of afferent axons in the visual cortex of monocularly deprived cats

The retrograde transport of horseradish peroxidase (HRP) was used to study the distribution of axonal terminals from the deprived and active laminae of the lateral geniculate nucleus (LGN) to the visual cortex in monocularly deprived cats. In two cats deprived from before natural lid opening, after injection of HRP in the visual cortex far fewer cells were labelled in the deprived than in the normal laminae of the LGN, implying that the distribution of their axons within the cortex had been reduced. One cat, deprived after an initial period in which both eyes were open, had much more equal labelling of deprived and normal laminae. These results suggest that a change in the ocular dominance of cortical neurones is sometimes, but not always, due to an actual loss of afferent fibres. © 1975.