Grouping visual features during binocular rivalry

During binocular rivalry, portions of one eye's view may be perceptually dominant while other portions are suppressed; at any given moment, overall dominance often resembles a patchwork mixture of the two eyes' views. This study investigates the potency of two Gestalt grouping cues--good continuation and common fate--to promote synchronous fluctuations in dominance of two, spatially separated rival targets. Two grating patches were presented to the left eye paired dichoptically with random-dot patches presented to corresponding right eye locations. The orientations of the two gratings were either collinear, parallel or orthogonal. Gratings underwent contrast modulations that were either correlated (identical contrast changes) or uncorrelated (independent contrast changes). Over 60 s trials, observers pressed one key when the left grating predominated, another when the right grating predominated and both keys when both were concurrently visible. Correlated contrast modulation promoted joint grating predominance relative to the uncorrelated conditions, an effect strongest for collinear gratings. Joint predominance depended strongly on the angular separation between gratings and the temporal phase-lag in contrast modulations. These findings may reflect neural interactions subserved by lateral connections between cortical hypercolumns.