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

Abstract

SUMMARY1. 1127 single units were recorded during oblique penetrations in area 17 of one normal, three monocularly deprived and four reverse sutured monkeys.2. 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.3. The presence in layer IV c of non-oriented, monocularly driven units, organized in alternating right-eye and left-eye 'stripes' (LeVay, Hubel & Wiesel, 1975) was confirmed.4. Early monocular deprivation (2-5j weeks) caused a strong shift of ocular dominance towards the non-deprived eye. However, 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 JVc the non-deprived eye's stripes were almost three times wider, on average, than the deprived.5. Later monocular deprivation (11-16 months) had no detectable influence on layer Ic but seemed to cause a small shift in ocular dominance outside IVc.Deprivation for 61 months in an adult had no such effect.6. After early reverse suturing (at 51 weeks) 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. 7. The later reverse suturing was delayed, the less effective was recapture by the originally deprived eye. Reversal at 8 weeks 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 weeks and most of them were non-oriented; reversal at 38j weeks had no effect.8. Binocular cells, though rare in reverse sutured animals, always had very similar preferred orientations in the two eyes. The columnar sequences of preferred orientation were not interrupted at the borders of ocular dominance columns.

Postnatal development of the visual cortex and the influence of environment

“…From these and similar experiments by us 13 , 15 and others 14,27 we conclude that the macaque monkey is highly susceptible to monocular deprivation during the first six weeks of life, at which age the sensitivity declines progressively, so that at 1½ to 2 years the monkey loses this type of neural plasticity. The length of the critical period varies between species.…”

“…10 we showed that the monkey was also susceptible to visual deprivation, 11 a finding subsequently confirmed and extended. 12,13,14,15 Further advances in our understanding of the nature of and mechanism underlying the deprivation phenomena depended on working out some of the functional architecture of the visual cortex. This was done through further physiological experiments in the normal animal and by using newly developed anatomical methods.…”

Rapid recovery from the effects of early monocular deprivation is enabled by temporary inactivation of the retinas

“…These findings establish 7 d of early MD in mice as a useful protocol to investigate strategies for reversing ocular dominance plasticity and promoting recovery from amblyopia. It has been known for many years from work in kittens and monkeys that deprivation-induced synaptic depression can be reversed if normal vision is restored in the weak (amblyopic) eye and the fellow eye is occluded (11,12). However, gains in the amblyopic eye often come at the expense of vision in the fellow eye, may be temporary, and are rarely accompanied by improvement in binocularity (9,(17)(18)(19).…”

“…This "reverse occlusion" approach has been validated in animals (11,12) and represents the cornerstone of current treatment (patching therapy) of human amblyopia (13)(14)(15)(16). However, this treatment has well-known limitations that include poor compliance, potential loss of vision through the newly patched eye, failure to recover binocular vision, and a declining treatment efficacy with age (15,(17)(18)(19)(20)(21).…”

Neural mechanisms of recovery following early visual deprivation

“…The extent to which the initial effects of deprivation can be reversed and the speed of the changes depend upon the age at which reverse occlusion begins (Blakemore & Van Sluyters 1974;Movshon 1976a;Blakemore et al 1978Blakemore et al , 1981. Indeed, it has been argued that the temporal profile of the declining ability to reverse prior deprivation-induced effects represents a separate critical period for recovery (Daw 1998(Daw , 2002(Daw , 2003Lewis & Maurer 2005).…”