Taylor J. Knickel^1,2, Stephen A. Engel^1,2; ¹University of Minnesota, Minneapolis, MN, United States., ²Center for Applied and Translational Sensory Science, University of Minnesota, Minneapolis, MN, United States.

Purpose: In binocular rivalry, two incompatible images are presented one to each eye, and perception alternates between the two. The primary hypothesis behind switches is adaptation, involving the weakening of the dominant stimulus. An alternative theory proposes that information from the suppressed eye accumulates, and switches occur when a threshold is reached. Here, we test for accumulation by transiently increasing the contrast of the suppressed stimulus to see whether this added information shortens the time to the subsequent switch (“dominance duration”), even if a switch was not immediately produced. Methods: Six observers viewed mid-contrast (0.15) orthogonal grating patterns presented one to each eye and reported their perception. Rivalry was measured in 80 second runs during which a one second Gaussian “pulse” was added to the suppressed stimulus. Five different pulse contrast levels (0.05, 0.1, 0.2, 0.4, 0.8) were used in different runs and could occur at two different onsets (zero or one second after a switch). 250 runs were collected over 10 sessions. Results: Dominance durations followed the gamma distributions typical of rivalry. For analysis, we only considered dominance periods that ended after the end of the pulse, effectively removing “breakthroughs” where a visible pulse caused an immediate switch. Overall, as the contrast of the pulse increased, mean dominance durations decreased monotonically from 3.77 seconds (no-pulse) to 2.504 seconds at 0.8 contrast. These effects were statistically significant within all observers for the highest contrast levels, (K-S Test, p < 0.001). Even the longest twenty percent of dominance durations, when switches occurred long after the pulse end, were reliably shortened. The effect of the pulse was relatively consistent between the two pulse onsets. Conclusion: The simplest account of these results is that information from the suppressed eye persists and can influence rivalry as it accumulates.

Acknowledgements: 5T32EY025187-09