Event-related Potentials Repetition Effect Research Articles

Modulation of event-related potentials (ERPs) by word repetition in a task with inconsistent mapping between repetition and response

ERPs were recorded during 5 blocks of a continuous recognition memory task. In each block words were shown twice, separated by an average of 6 intervening items, and the task was to respond discriminatively on the basis of whether each word was appearing in that block for the first (first presentations) or the second (second presentations) time. In blocks 2–5, half of the words had also been shown in the immediately preceding block, and half were new to the experiment. Subjects were slower and less accurate at identifying first presentations of words that had appeared in the preceding block, as compared to first presentations of entirely new words. In the latency ranges of the N400 and late positive components, ERPs to words that had previously been presented were more positive-going than were ERPs to new words. These ‘across-block’ ERP repetition effects were qualitatively very similar to, and additive with, those evoked by words repeated within a block. These findings suggest that the effects of word repetition on ERPs are not dependent on an invariant mapping between repetition and response and are not a consequence of facilitated decision/response processing for repeated items.

A developmental study of event-related potentials during explicit and implicit memory

Event-related potentials (ERPs) were recorded from children, adolescents and adults in response to drawings of common objects or their printed names. Explicit memory was assessed in a continuous recognition paradigm, where each item had (old) or had not (new) been presented earlier. Implicit memory was assessed in separate blocks of pictures and words where item repetition was incidental to the assigned task of identifying stimuli in a given semantic category. Accuracy measures replicated the finding that word memory decays more rapidly than picture memory. A larger anterior negativity to pictures than words in children, but not adolescents or adults, suggested the existence of separate picture/word processing mechanisms that undergo developmental change. ERP repetition effects involved at least two components: a negativity that was larger to new items in both tasks, and a subsequent centroparietal positivity, most likely P3b, that was larger in response to old items for the explicit task only. Both components did not appear to undergo developmental change.

The contributionof task-related factors to ERP repetition effects at short and long lags

Event-related potentials (ERPs) were used to assess the relative contribution of task-related decision-making processes to the repetition effect at Lags 0 and 15. Electrophysiological activity was recorded from 16 subjects in two tasks. Task A required a lexical decision: subjects were instructed to silently count infrequently occurring nonwords in a list of words and nonwords. Task B, a recognition memory task presented in four blocks, required subjects to distinguish between old and new probes in each block. Significant ERP repetition effects, equivalent in both tasks, were found at Lag 0. In contrast, at Lag 15, the repetition effect was significant only in Task A. These results suggest that ERPs are sensitive primarily to poststimulus-identification sources of the repetition effect, such as the recovery of episodic traces related to stimulus-categorization and decision-making processes.