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.