Abstract
Binocular combination of monocular inputs transpires within cortical neurons that vary in ocular dominance, owing to developmental and experiential influences that govern the strengths of innervation from the two eyes1. Accordingly, binocular experience may vary within the visual field due to regional imbalances that impact effective signal strengths from the two eyes. Rather than having a single dominant eye, people may have regional differences in sensory eye dominance (SED)2,3. Using binocular rivalry, a competitive phenomenon with dynamics sensitive to the stimulus strength of competing monocular images, we mapped patterns of SED in observers’ visual fields. Observers tracked perceptual alternations while dichoptically viewing dissimilar monocular stimuli imaged at various visual field locations. Results reveal that the relative predominance of the two eyes can vary widely across the visual field, with some locations promoting equal balance and others strongly biased toward one eye (see Figure). Results were reliable across sessions (r=0.55, p< 0.0001), especially for regions of strong SED imbalance (locations with >10% difference in predominance on both runs, r=0.70, p< 0.0001). Importantly, SED appears to function like a reduction in effective contrast for the weaker eye – the amount of balancing contrast required by the weaker eye to equate predominance for the two eyes is closely predicated by the magnitude of SED imbalance (r=0.85, p< 0.01). These results indicate that SED relies on local mechanisms that are idiosyncratic within the visual fields of typical observers. Such naturally occurring variability in the effective contrast contributed by the two eyes may have widespread impact on binocular functions such as stereopsis, where contrast imbalances produce impaired stereoacuity. Within a subset of observers tested, stereopsis is indeed impaired in regions of the visual field with pronounced SED. Continuing investigations are exploring the impact of regional inter-ocular contrast variations on other binocular functions.
Meeting abstract presented at VSS 2015