Changes in the distribution of geniculocortical projections following monocular deprivation in tree shrews

We examined changes in the percentages and distribution of labelled geniculate (LGN) cells following injection of HRP into the striate cortices of normal and monocularly deprived tree shrews. Results show that deprivation does not affect the percentage of labelled cells but does alter the distribution. The projection column of labelled cells is much narrower in deprived than in non-deprived layers suggesting that the axons of non-deprived LGN cells either extend across greater distances in cortex to reach the injection sites or have more peripheral terminal sites available for transport than deprived counterparts. This finding indicates that, although ocular input to tree shrew striate cortex is organized in the form of horizontal strips, not columns, binocular competition still results in alterations in the growth of geniculocortical axons.