Grand-average ERP waveforms of the current Experiment.

<p>(A) Grand average waveforms elicited by the four conditions at selected electrode sites. Waveforms are time-locked to the onset of the critical words and negative amplitude is plotted up. (B) Topographies of the difference wave formed by subtracting ERPs to the topic shifted/congruent from topic shifted/incongruent (a), and ERPs to the topic maintained/congruent from topic maintained/incongruent (b) in selected time periods.