EXTENT OF RECOVERY FROM THE EFFECTS OF VISUAL DEPRIVATION IN KITTENS

Abstract

In kittens monocular or binocular deprivation by lid suture for the 1st 3 months of life leads to virtual blindness, marked morphological changes in the lateral geniculate body, and a severe deterioration of innate cortical connections. In 7 kittens whose eyes had been sutured, 6 unilaterally and 1 bilaterally, an attempt was made to assess the extent of recovery, by reopening an eye and allowing the animals to live for another 3-15 months. In 2 of the monocular closures the deprived eye was opened and the normal eye closed. In all kittens there was some slight behavioral recovery during the 1st 3 months, but the animals remained severely handicapped and never learned to move freely using visual cues. There was no morphological improvement in the lateral geniculate body. Our previous impression that atrophy can develop with deprivation beginning at 3 months was confirmed. In monocularly deprived animals a few cells in the striate cortex developed responses to stimulation of the originally deprived eye, but in many of these cells the responses were abnormal. In the binocularly deprived kitten there was a marked increase in the proportion of cells responding abnormally to the eye that was reopened, without any obvious increase in the total number of cells responding to that eye. We conclude that the animal''s capacity to recover from the effects of early monocular or binocular visual deprivation, whether measured be-haviorally, morphologically, or in terms of single-cell cortical physiology, is severely limited, even for recovery periods of over a year.