EEG time-frequency analysis.

(A) The upper panel shows spectral power from 5 to 50 Hz averaged over all 57 scalp electrodes for the first four ratings (data for later ratings are missing for some participants, who always responded earlier), baseline corrected to the 500 ms before the first rating. The white, horizontal lines indicate the range of beta frequencies (14–30 Hz). The lower panel shows the power in the beta-band. A general negative trend in the signal and the alternation between de- and increases at every rating are clearly visible. (B) Position of scalp electrodes. The 37 labeled electrodes show the expected effect in the beta band (i.e., lower average signal in the first half of each rating than in the second half) at p<.001. Note that all EEG analyses are restricted to ratings at which no response was made.