Electrophysiological Correlates of Reversal Processes in Ambiguous Figure Perception

Ambiguous figures provide an opportunity to study fluctuations in perceptual experience without corresponding changes in sensory input. Researchers have taken great interest in the mechanisms that generate them using electrophysiology because of the potential to track these processes across time as perceptual reversals of these figures unfold. This work has highlighted brain activity both before and after perceptual reversals involving a wide range of mechanisms. Some of the known electrophysiological correlates of perceptual reversals, like the Reversal Negativity (RN) and Reversal Positivity (RP), have the potential to be explained by demands of the tasks used to elicit them. In addition, many findings on perceptual reversals and ambiguous figure interpretation originate from studies using univariate analyses that do not take full advantage of the multivariate nature of EEG data. In four experiments, I used psychophysics, ERP, and multivariate pattern analysis (MVPA) of EEG data to address the interpretation of two reversal-related ERP components and to identify new multivariate correlates of perceptual reversals. First, I found that the reversal-related RP only appears when reversals are response targets. This result suggests that the RP is not a pure correlate of perceptual processing of endogenous perceptual reversals but rather may reflect response-related monitoring processes. Second, using MVPA, I found that activity linked to perceptual reversals in the post-stimulus period is an ongoing process that involves a wide range of frequency bands (1-30Hz) and spans over a substantial amount of time (~550 ms). Finally, I found that I was able to isolate in time and frequency pre- stimulus activity that is predictive of the upcoming subjective interpretation of the ambiguous stimulus and of perceptual reversals. Overall, these results provide a new interpretation for some extant reversal-related electrophysiological markers as well as identify a set of new phenomena to guide neural theories of perceptual reversals going forward.