Instantaneous alpha
We extracted instantaneous alpha, according to Cohen’s method, as a within-participant measure for time resolved changes in peak alpha frequency between trials. We computed instantaneous alpha for the electrode used in the previous analysis, B7 and, following the protocol of the original study, also for electrode C16, which had the highest amplitude in the alpha band for most participants in the pre-stimulus EEG data. We then compared pre-stimulus instantaneous alpha frequency between correct and incorrect responses. The mean instantaneous alpha extracted from electrode B7 was 10.361 Hz (SD = 0.023) for correct responses and 10.363 Hz (SD = 0.025) for incorrect responses. For electrode C16, mean instantaneous alpha frequency for correct answers was 10.318 Hz (SD = 0.039). For incorrect answers it was 10.326 Hz (SD = 0.026). Cluster-based permutation testing revealed no time clusters with a statistically significant difference in instantaneous alpha between correct and incorrect answers for either electrode (Fig 4).
Figure 4: Within subject analysis of instantaneous alpha for correct (blue) versus incorrect (orange) responses. Left: instantaneous alpha extracted from electrode C16. Right: instantaneous alpha extracted from electrode B7. Shaded regions indicate ± standard error of the mean.