Abstract
During binocular rivalry, two incompatible monocular images compete for perceptual dominance, with each being in turn visible for a few seconds while the other is suppressed. Why a percept should persist in awareness despite strong competition is unclear. Here, we investigated the hypothesis that a mnemonic process is involved in perceptual maintenance by measuring brain activity during temporary removal of rivalrous stimuli, when the stimulus perceived on reappearance tends to be the one in awareness as they disappeared.
In a behavioral experiment, we demonstrated in 14 human subjects that percept maintenance across periods of stimulus removal was specific to binocular rivalry between monocularly presented face and grating stimuli, compared to a replay condition where the same stimuli where shown in physical alternation.
The same group of subjects also underwent fMRI at 3T. During both rivalry and replay, activity in the fusiform face area (FFA) was greater during face as compared to grating perception, replicating previous findings. Critically, FFA activity during periods of stimulus removal was higher when the last stimulus in awareness before disappearance was a face, rather than a grating. This face-specific signal was specific to rivalry, as FFA activity following physical alternations of the stimuli did not show such a difference. Moreover, the individual tendency to maintain a face percept across periods of stimulus removal strongly correlated with activity in prefrontal and parietal regions previously implicated in working memory.
In conclusion, our findings provide evidence for a new type of involuntary perceptual memory that stabilizes rivalrous visual perception.
This work was supported by the German Research Society (PS) and the Wellcome Trust (GR)