Abstract
Halos around lines, patches of coherent dominance, and traveling waves have been observed during binocular rivalry, which all imply some spatial spread in the interocular inhibition field of competing regions of space. The current series of experiments show that the range across which a target bar is rendered invisible during rivalry depends greatly on the luminance pattern defining the bar. Rectangular target bars, which were of uniform luminance, random noise, or filled with gratings oriented either parallel or perpendicular to the orientation of the target bar, were presented to one eye. Presented to the other eye were two rectangular suppressor bars equidistant from the center of the target bar. For horizontal target bars, the range of suppression was approximately 1 deg for target bars of uniform luminance or filled with a grating of parallel orientation, but only 0.5 deg for target bars filled with random noise or a grating of perpendicular orientation. For vertical target bars, the total time of suppression decreased by 20% or more, but the pattern of results with regards to the luminance profile of the target bar was very similar. Nevertheless, the inclusion of a small gap between the suppressor bars and the central portion of the target bar greatly reduced the frequency with which the target bar was rendered invisible. Also, the spread of suppression is likely not due to traveling waves in dominance, as no change in the time until suppression was observed as a function of the separation of the suppressor bars. Consistent with all of the results is that interocular inhibition fields extend 1–2 deg, but that the likelihood of interocular suppression occurring is mitigated by the nature of the luminance pattern perpendicular in orientation to the suppressors. The implications for models of interocular suppression will be explored.
Work supported by NSERC Grant OP227224 and Canadian Institute for Advanced Research.