The rate of recovery of vision after early monocular deprivation in kittens

Abstract

3. The initial effects of monocular deprivation were graded in severity according to the age at which the deprivation was imposed, ranging from apparent blindness in animals deprived at 6 weeks of age to only a small loss of acuity in kittens deprived at 12 weeks of age.4. The effects of deprivation imposed from birth were particularly severe, leading to a temporary blindness. Nevertheless after a period of time that became progressively longer with increasing deprivation, all animals showed some recovery of pattern vision over the course of the next 2 or 3 months. The extent of this recovery became progressively less as the period of deprivation was prolonged. There was even some recovery of vision (an acuity of 2-5 cycles/deg) in animals that were deprived throughout the duration of the 'critical period' to 4 months of age.5. Direct comparison of the rate of behavioural recovery between animals that were reverse sutured with that of litter-mates that received binocular input after monocular occlusion to either 45 or 60 days of age proved to be remarkably similar, although the acuity that was eventually attained by the reverse sutured animals was always slightly higher.6. The recoveries observed after reverse suturing were reasonably well correlated with changes observed in the ocular dominance of visual cortical cells under similar circumstances. 7. Although the recovery in these animals can be accounted for by the simple notion of a competitive interaction between the two eyes, the recovery observed in animals that had both eyes open after the initial period of deprivation cannot be so readily explained. Evidently there must be an additional non-competitive mechanism of recovery.

Neural mechanisms of recovery following early visual deprivation

“…The anatomical and physiological changes observed in V1 as a consequence of early monocular deprivation are accompanied by a loss of visual acuity in the DE, the severity of which depends on when the deprivation began and its duration (Giffin & Mitchell 1978). On the other hand, the loss of binocularly excitable cells in animals reared with exotropia is accompanied by a loss of stereoscopic vision without any appreciable impairment of the vision of either eye (Mitchell 1988).…”

Initial recovery of vision after early monocular deprivation in kittens is faster when both eyes are open

“…The challenge to models based on binocular competition stems from the fact that restoration of normal visual input to the deprived eye without concurrent manipulation of the visual input to the nondeprived eye does little or nothing to reduce the very substantial competitive advantage of this eye. Past measurements of the speed of recovery of visual acuity of the deprived eye after MD during BR suggest that it may rival that observed with reverse lid-suture (RLS), where the formerly nondeprived eye is deprived to provide a competitive advantage to the formerly deprived eye (5,7,9).…”

“…However, not all experimental findings can be readily accommodated by mechanisms based on binocular competition. A striking case in point is the substantial recovery of both ocular dominance in the visual cortex of cats and of the vision of the deprived eye in cats and humans after MD in the situation (binocular recovery, BR) where both eyes are open during the recovery period (5)(6)(7)(8). The challenge to models based on binocular competition stems from the fact that restoration of normal visual input to the deprived eye without concurrent manipulation of the visual input to the nondeprived eye does little or nothing to reduce the very substantial competitive advantage of this eye.…”

Enhancement of Vision by Monocular Deprivation in Adult Mice

“…A classic finding of mammalian visual plasticity studies is that monocular deprivation (MD) causes lasting physiological effects, a shift of ocular dominance (OD) away from the deprived eye in binocular primary visual cortex (V1) (Wiesel and Hubel, 1963;Hubel and Wiesel, 1970), and behavioral changes, a loss of spatial vision (amblyopia) through the deprived eye (Giffin and Mitchell, 1978), only if deprivation occurs during a "critical" period in juvenile life. Recent physiological studies in mice (Sawtell et al, 2003;Pham et al, 2004;Hofer et al, 2006) have challenged the notion of a restricted period of OD plasticity in cortex by showing that MD in adulthood causes a transient enhancement of responses selectively through the nondeprived eye.…”