Recovery from monocular deprivation in the monkey. III. Reversal of anatomical effects in the visual cortex

Transneuronal autoradiography was used to study the effects of visual deprivation on the ocular dominance stripes in layer IV c of the striate cortex of Erythrocebus patas (Old World) monkeys. The animals were studied after: (a) 21–28 days of monocular deprivation starting at, or within, a few days of birth; (b) the same treatment followed by a further 3, 6, 15 or 126 days of monocular vision through the originally closed eye (reverse suturing), or followed by 15 or 96 days of vision through both eyes (reopening). One other monkey was monocularly deprived from birth to 189 days. In most cases the behaviour of the ocular dominance stripes formed by the initially closed eye was studied. After 24 days of monocular deprivation from birth, the input from the normal eye was distributed uniformly within layer IV c, with no periodicity evident. After 21 days of deprivation, the deprived eye’s input formed narrow stripes occupying about 38% of layer IV c in the operculum. Seven months of monocular deprivation reduced this to about 29%. Opening the closed eye after the deprivation produced no change in the area innervated: when periods of 15 or 96 days of binocular vision followed the deprivation, the areas innervated by the initially deprived eye were 26 and 30% respectively. However, in both cases the deprived eye’s input formed blobs and spots, rather than uniformly narrow stripes. In contrast to reopening, reverse suturing increased the fraction of layer IV c occupied by input from the initially deprived eye. In the operculum, the effects of reverse suturing appeared to be fully developed after only 6 days of reversal: the initially deprived eye’s stripes having expanded to occupy about 50% of layer IV c. A further 9 days’ reversal produced little change in this. In the visual cortex in the calcarine fissure, the effect of the initial deprivation was more severe, and the expansion induced by reverse suturing more pronounced. The initial deprivation caused the stripes to shrink to occupy 24% of layer IV c; after 6 days of reverse suture the proportion increased to 52%, while after 15 days of reverse suture about 88% of IV c was occupied. These results show that reverse suturing can cause fresh growth of afferent axons in regions of layer IV c from which they had been at least partially removed, either by the normal process of segregation, or as a consequence of monocular deprivation. Taken in conjunction with the findings of the accompanying two papers (Blakemore et al. 1981; Garey & Vital-Durand 1981) they also suggest (a) that there is a close relationship between the extent of layer IV c innervated and cell size in the lateral geniculate nucleus, and (b) that many of the physiological consequences of deprivation experiments are secondary to anatomical changes in the distribution of afferents from the lateral geniculate nucleus.