Abstract
Mutual binocular inhibition is unequal in people with sensory eye dominance (SED). We found SED can be reduced using a Push-Pull perceptual training paradigm where the weak eye was cued before the two eyes were stimulated with a pair of orthogonal gratings (Xu et al, Neurosci. Abst, 2009). The pre-cueing ensured the grating in the weak eye was perceived so that the observer could discriminate its orientation, while the strong eye was interocularly suppressed. The impact of the training was limited to the trained retinal location and grating orientation. However it is unknown whether top-down attention, which directs orientation discrimination in the weak eye, is required for the learning. We investigated this by implementing a 10-day Push-Pull training. During the training, two pairs of orthogonal grating discs (vertical/horizontal, 1.25deg, 3cpd, 35cd/m2) simultaneously stimulated two different retinal locations (2 deg from the fovea). While both retinal locations in the weak eye were pre-cued, observers were instructed to attend to and discriminate the grating orientation in one location (attended), and ignore the other (unattended). We found SED gradually reduced with training, both at the attended and unattended locations. This indicates top-down attention is not required for the learning. Top-down attention, however, is facilitative as the reduction in SED was larger at the attended location. The consequences of reduced SED are also evident in two unrelated binocular visual tasks. One, using a binocular rivalry tracking task, we found the predominance of seeing the dominant image in the weak eye was significantly enhanced. The enhanced predominance effect was slightly larger at the attended location than at the unattended location. Two, we found the training caused a similar improvement in stereoacuity at both locations. These findings show that with the Push-Pull training paradigm, top-down attention is not obligatory, but can facilitate perceptual learning.