Updating of context in working memory: an event-related potential study.

Flexible control of behavior depends on the representation, maintenance, and updating of context information in working memory, which is thought to rely on the prefrontal cortex (PFC). However, in contrast to maintenance, the dynamics of context activation and updating have not been well studied. To identify neural signals associated with context updating, we compared event-related potentials associated with cues that did or did not provide task-relevant context information. The earliest effect of context was detected 200 msec following cue onset and had a scalp topography consistent with a generator in the PFC. Subsequent effects of context were detected at 400-700 msec following cue onset (P3b), with a broad scalp distribution spanning posterior areas, and during the final 300 msec preceding the target, with a probable generator in the medial frontal cortex. We propose that the effect of context on P2 is consistent with the onset of context updating in the PFC. Subsequent components may be indicative of activation of task-relevant posterior regions and context maintenance.