The relationship between relative eye usage and ocular dominance shifts in cat visual cortex

A novel modification of the alternate monocular deprivation paradigm was used to quantitatively define the relationship between relative eye usage and the shift in visual cortical ocular dominance toward the advantaged eye. Both eyes of cats were alternately occluded by contact lenses during daily visual exposure sessions with varying ratios of relative eye usage: 1:1, 1.7:1, 3:1, 7:1, 50:1, 100:0. Only 100:0 and 50:1 ratios produced an ocular dominance shift in favor of the more experienced eye. The ocular dominance shift in 100:0 cats occurred in all cortical layers but only in extragranular layers of 50:1 cats. A steep power function described the data, indicating that an extreme imbalance in relative eye usage (>90%) is required for an ocular dominance shift.