An electrophysiological analysis of maintenance and manipulation in working memory

Although maintenance and manipulation are generally recognized as the most basic processes underlying the online use of information, the temporal characteristics of these two processes are still to be clarified. In this study, brain activity associated with reflecting or maintaining a visual stimulus (manipulation and maintenance conditions) was investigated with a delayed-matching-to-sample task using event-related potentials (ERPs). Compared with maintenance, manipulation elicited more positive ERPs at 400-750 ms after delay-period onset, an effect distinct from what has been observed with mental rotation. Negative slow waves were also found at left central-parietal regions at 1750-2400 ms and were more negative for manipulation than for maintenance, which indicated that subjects may repeat the reflecting strategy to obtain accurate spatial information.