Changes in the Visual Cortex of Rats after Unilateral Deprivation

It is shown that the volume of the visual cortex was diminished in the deprived hemisphere, layers II–IV being most affected, and a significantly higher cell density was found in layer IV on the deprived side.

Abstract

THE visual system, is especially suitable for showing the effects of sensory deprivation on the morphology of the corresponding brain centres. In this system, different types of deprivation or excessive stimulation induce changes in cell density1,2, dendritic branching3 and formation of dendritic spines4–7. We have been able to show quantitative morphological changes in cortical as well as subcortical visual centres after unilateral visual deprivation in rats8. As a result of this treatment, the volume of the visual cortex was diminished in the deprived hemisphere, layers II–IV being most affected. A significantly higher cell density was, however, found in layer IV on the deprived side. This relative increase in the density of neurones was thought to be the result of diminished dendritic branching of receptive neurones in this layer. The field of contact could result in a reduced number of receptive spines on the apical dendrites of the pyramids in layer V, passing through layer IV.