Relationship between the PAF and bistable perceptual grouping.

(A) The normalized amplitude obtained through an FFT from all the bistable trials (from –800 to 0 ms relative to the onset of the first frame) collapsed over all electrodes in all the participants revealed a clear peak at the alpha frequency. The gray shading indicates ±1 SEM. The light gray rectangle indicates the selected frequency band. (B) The amplitude topographic map of the selected alpha frequency band (8–13 Hz) revealed a clear posterior scalp distribution. The selected posterior electrodes are indicated with white dots. (C) The frequency of occipital alpha in each individual subject, derived from the prestimulus alpha activity, was significantly correlated with the individual transition IFI threshold. Dashed lines indicate 95% confidence intervals around the linear fit line. (D) Within-subject analysis of the instantaneous PAF revealed higher alpha frequency preceding the bistable GM trials than the bistable EM trials. Significant time points are indicated by the horizontal black bar (cluster-based correction, p https://osf.io/tze94/. a.u., arbitrary unit; EM, element motion; FFT, Fast Fourier Transform; GM, group motion; IFI, interframe interval; PAF, prestimulus alpha frequency; SEM, standard error of the mean.