Schizotypy, Symmetry Processing and EEG Aperiodic Activity: Behavioral and Electrophysiological Associations

Attenuated schizophrenia traits vary continuously in the general population and may be associated with altered perceptual organization and background neural activity. One proposed contributor to perceptual aberrations is variability in ongoing neural activity, or neural noise, for which EEG aperiodic activity has been investigated as a potential electrophysiological correlate. This study examined the associations between schizotypy, resting-state EEG aperiodic activity and symmetry perception. Seventy-eight healthy adults completed the O-LIFE-S questionnaire, two resting-state EEG recordings and a symmetry detection task with varied dot numerosity. Aperiodic exponent and offset were extracted from the resting state power spectra, and the Sustained Posterior Negativity (SPN) amplitude was quantified as the mean symmetry and asymmetry ERP difference from 250 to 600 ms. Trial-level binomial generalized linear mixed-effects models characterized the nonlinear relationship between dot numerosity and accuracy and tested moderation by aperiodic activity. Aperiodic exponent and offset were stable across the session, a clear SPN was elicited, and accuracy showed a significant inverted-U-shaped relationship with dot numerosity. However, total schizotypy did not significantly predict aperiodic exponent, offset, or SPN amplitude. Neither exponent nor offset significantly moderated the nonlinear accuracy function, and secondary analyses provided no evidence for associations with individual schizotypy dimensions. These results may reflect the sample characteristics, possible compensatory mechanisms in schizotypy or incomplete correspondence between aperiodic activity and neural noise. Larger and more diverse samples, as well as spectral rotation analysis and separation of SPN phases may clarify the relationships.