Relationship between amblyopia, LGN cell "shrinkage" and cortical ocular dominance in cats.

Six cats were reared with surgically produced squint or atropinisation of one eye during the sensitive period of development. Five cats were reared without an ocular interference but in the same environment as the experimental cats. Four of these normally reared cats provided control data for perikaryal size. When the cats were 5-8 months old, the ocular dominance distribution of cells in area 17 of the visual cortex was determined, and measurements of visual acuity of cells in the LGN receiving inputs from the area centralis were carried out. Following the neurophysiological experiments, the perikaryal sizes of LGN cells receiving fibres from the area centralis of the left and right eye were measured from Nissl stained sections of the brain of each cat. Cats which showed greater amblyopia (loss of acuity) of LGN cells driven from the area centralis of the experimental eye, showed a greater degree of apparent "shrinkage" of Nissl stained LGN cells and greater proportion of cortical cells excited by the control eye than by the experimental eye. All experimental cats showed a loss of binocularly driven cells, regardless of whether their LGN cells were amblyopic or not, and whether they had "shrunk" or not. However, when LGN cell amblyopia was present, the degree of amblyopia and "shrinkage" of the LGN cells were correlated with the degree of loss of binocular cells also.