Atypical Binocular Rivalry Dynamics of Simple and Complex Stimuli in Autism
Objectives: First, we hoped to replicate our previous finding of a slower rate of rivalry with longer mixed percepts in ASC in a new, expanded sample of participants. Second, we tested whether this finding was selective for stimuli of a particular level of visual complexity.
Methods: 53 participants (26 with ASC) completed twelve 40s trials of binocular rivalry (6 with object stimuli, 6 with grating stimuli) and 24 control trials. Participants continuously reported either dominant or mixed percepts throughout the trial. We analysed the rate of perceptual transitions and average percept durations as well as ratios of percept durations.
Results: We tested rivalry dynamics with Stimulus Type as between-subject factor and ASC Diagnosis as within-subject factor in repeated measures ANOVA. ASC subjects perceived a lower rate of switches (F(1, 51) = 4.3, p < 0.043) with longer mixed percepts (F(1, 51) = 14.7, p < 0.001). The differences in average mixed percepts and proportion of mixed percepts were confirmed with non-parametric comparisons of means to be significant in both stimulus conditions, while the difference in switch rate was significant only in the grating condition.
Conclusions: We replicate our previous findings of a slower rate of binocular rivalry with increased mixed percepts in ASC, and show that these effects are present at low levels of stimulus complexity. These results are predicted by an increased ratio of excitatory/inhibitory synaptic transmission in autism, and suggest that this imbalance may manifest as early as V1.