Morphological and physiological changes in the monkey visual system after short-term lid suture.

The effects of short-term unilateral form vision deprivation by suturing the lids in macaques were evaluated in terms of cortical neuronal electrophysiology and cell sizes in the lateral geniculate nucleus (LGN). The results show that cell shrinkage in the LGN is proportional to the duration of lid closure, with the parvocellular laminae being somewhat more sensitive than the magnocellular layers. Conversely, the electrophysiologically demonstrable shift of cortical dominance in favor of the nondeprived eye occurs after only 1 week of deprivation, with equal severity in short-term and long-term deprived monkeys, and precedes the appearance of histological abnormalities in the LGN. This increased cortical vs. geniculate sensitivity to visual deprivation is further demonstrated by the findings that (1) lid closure near the end of the second month of life does not affect the LGN cell size but causes the cortical electrophysiological deprivation effect and (2) the cortical eye dominance but not the size of the geniculate cells can be reversed in favor of the previously deprived eye by surgical closure of the formerly dominant eye.