Figure 3.
Relation between perception and oscillatory activity. A, Statistical significance of the power difference at channel Fz between hits and misses (left panel), evaluated with a resampling test. Alpha power (6–12 Hz) preceding stimulus onset was significantly stronger for misses than for hits. The color map represents uncorrected p values and the white outline delimits significant effects corresponding to an FDR of 5%. The right panel shows the relationship between spectral power in the alpha band (8.2 Hz) at −492 ms and performance after single trials were pooled in 10 power bins. The horizontal line indicates average performance (standardized to 1) across all bins. Error bars represent SEM. Performance is superior on trials with lowest alpha power (1-way ANOVA, p < 0.0165). B, Statistical significance of phase bifurcation between hits and misses at channel Fz (left panel); axes and conventions are as in A. At ∼7 Hz and −120 ms prestimulus, hits and misses are associated with different phase angles. Top inset, The circular histograms of mean phase angles at 7.1 Hz and 120 ms for hits and misses across participants. Phases were pooled into four phase bins. The distance from the origin indicates the number of subjects falling within a bin, and the angles indicate the lower bound of each phase bin. Bottom inset, Close-up on the 55 time–frequency points with significant phase bifurcation that satisfy an FDR of 5%. The right panel shows the relationship between phase (at 7.1 Hz; −120 ms) and standardized performance after phases were aligned for each subject so that the optimal phase corresponds to a zero phase angle. Performance declines to a minimum at the opposite phase angle (1-way ANOVA, p < 0.01).