Figure 3. Pre- and peristimulus alpha suppression determine perceptual accuracy.
(a) Frequency spectra show prestimulus alpha suppression (interval [–1 0] s before target onset) for detected (hits, green) versus undetected targets (misses, yellow) averaged over bilateral parieto-occipital sensors (see inset). (b) Left panel shows the topographic distribution of normalized prestimulus power differences between detected and undetected targets (i.e., hits and misses). ROI channels with significant alpha-band differences (computed between [Arnal and Giraud, 2012; Busch and VanRullen, 2010] 8–13 Hz) for the contrast hits> misses are marked. Right panel shows the corresponding group-level t values from cluster-corrected permutation testing. Significant channels are marked for reference. (c) TFR shows power difference for the contrast hits> misses averaged across ROI sensors. Differences were computed on a frequency range of 5–40 Hz within a time frame of [–1 0.2] s around target onset, red frame indicates alpha frequencies (8–13 Hz). (d) Population statistic quantifying TFR differences (see panel (c)) on the sensor level. For each frequency at each time point, the heatmap illustrates which ratio of the n=82 ROI channels showed a significant difference for the contrast hits> misses (cluster-corrected, see main text).
Figure 3—figure supplement 1. Band-specific topographies over time.
