Figure 6.

Grand average source waves, latencies, and amplitudes for Experiment 3. The data represent an average over 6 subjects, where each trace is based on 200 (1:1, 400) replications per subject. The activity is averaged over right and left hemispheres. (A) Control condition: periodic unipolar (black) and alternating-polarity (gray) CTs were alternated with irregular CTs. (B) Continuous alternation of unipolar and alternating-polarity CTs (not interspersed with irregular CTs). The baseline was set 100 ms before the onset of the unipolar CT (black curves), corresponding to the schematic stimulus (t = 0 ms is aligned to the onset of the unipolar CT). For comparison, the baseline was also set before the onset of the alternating-polarity CT (gray curves, no corresponding scheme), and the onset was aligned to the same position. The duration of unipolar and alternating-polarity CTs was 720:720 ms (1:1), 1440:1440 ms (2:2), 720:2160 ms (1:3), or 2160:720 ms (3:1). (C) Mean latencies of the N₁m and P₂m at the transition from alternating polarity to unipolar (black) and at the transition from unipolar to alternating polarity (gray). N₁m measurement interval 100-250 ms, P₂m measurement interval 150-350 ms. (D) Amplitudes of the sustained field shift (average in the interval 400-720 ms), (E) Peak-to-peak amplitudes (N₁m-P₂m) for the transient response evoked at the transition from alternating polarity to unipolar, and (F) at the transition from unipolar to alternating polarity. Small circles indicate the unipolar/alternating transition and large circles the alternating/unipolar transition. Error bars indicate the standard error of the mean. Symbols connected by solid lines represent values measured without high-pass filtering (like the source waves in A); those connected by dashed lines were measured with a 3-Hz high-pass filter (Butterworth, zero-phase shift).