The physiological effects of monocular deprivation and their reversal in the monkey's visual cortex.

Abstract

Single units (1127) were recorded during oblique penetrations in area 17 of 1 normal, 3 monocularly deprived and 4 reverse sutured monkeys [Cercopithecus aethiops, Erythrocebus patas and Macaca fascicularis]. In all animals most cells outside layer IVc were orientation-selective, and preferred orientation usually shifted from cell to cell in a regular progressive sequence. The presence in layer IVc of non-oriented monocularly driven units, organized in alternating right-eye and left-eye stripes (LeVay, Hubel et Wiesel, 1975) was confirmed. Early monocular deprivation (2-5 1/2 wk) caused a strong shift of ocular dominance towards the non-deprived eye. Even outside layer IVc, neural background and some isolated cells could still be driven from the deprived eye in regularly spaced, narrow columnar regions. In layer IVc the non-deprived eye''s stripes were on the average almost 3 times wider than the deprived. Later monocular deprivation (11-16 mo.) had no detectable influence on layer IVc but seemed to cause a small shift in ocular dominance outside IVc. Deprivation for 6 1/4 mo. in an adult had no such effect. After early reverse suturing (at 5 1/2 wk) the originally deprived eye gained dominance over cells outside layer IVc just as complete as that originally exercised by the eye that was first non-deprived. The later reverse suturing was delayed, the less effective was recapture by the originally deprived eye. Reversal at 8 wk led to roughly equal numbers of cells being dominated by each eye; fewer cells became dominated by the newly open eye after reverse suturing at 9 wk and most of them were non-oriented; reversal at 38 1/2 wk had no effect. Binocular cells, though rare in reverse sutured animals, always had very similar preferred orientations in the 2 eyes. The columnar sequences of preferred orientation were not interrupted at the borders of ocular dominance columns. Even within layer IVc there was evidence for re-expansion of physiologically determined ocular dominance stripes. After early reverse suture, stripes for the 2 eyes became roughly equal in width. Possible mechanisms for these changes are discussed.