Examining the role of adaptation in spontaneous perceptual reversals of ambiguous motion stimuli

Dundas, Kimberley

Abstract

The cause of spontaneous perceptual reversals of visually ambiguous stimuli has been attributed to several different mechanisms. One hypothesis suggests that adaptation, or “neural fatigue”, builds up while one interpretation is dominant and eventually triggers a reversal. Although there is behavioural evidence that adaptation to an unambiguous stimulus (e.g., directional motion) can bias subsequent perception of an ambiguous one, it is unclear whether that adaptation plays a role in spontaneous reversals. In three experiments, we used psychophysical, ERP and multivariate pattern analysis (MVPA) of EEG data. Our behavioural results confirmed that adaptation to directional motion does indeed bias subsequent perception of ambiguous motion. We then used MVPA of EEG data to test whether that adaptation is involved in spontaneous perceptual reversals. We did this by training a machine-learning classifier on the pattern of EEG scalp voltage during adaptation-induced reversals. We then tested this classifier on spontaneous reversal data and found above-chance decoding and similar activity patterns. To shed light on the statistical power of the MVPA technique used to generate our results, we ran a series of simulations that manipulated effect size and sample size. We found that statistical power of the MVPA pipeline employed in this thesis and commonly in the wider literature, indeed increased when larger sample sizes were used as well as when larger effect sizes were added to the simulated data. Taken together, the results from this thesis suggest that similar brain mechanisms mediate perceptual adaptation and spontaneous perceptual reversals, providing support for the “neural fatigue hypothesis” of multi-stable perception. Additionally, the analyses used to generate this claim have been shown to be sufficiently powerful in which to detect these effects.

Citation

Dundas, K. Examining the role of adaptation in spontaneous perceptual reversals of ambiguous motion stimuli. (Thesis). Keele University. Retrieved from https://keele-repository.worktribe.com/output/956391

• Thesis Type: Thesis
• Deposit Date: Oct 28, 2024
• Publicly Available Date: Oct 28, 2024
• Public URL: https://keele-repository.worktribe.com/output/956391
• Award Date: 2024-10