Parahippocampal Reactivation Signal at Retrieval after Interruption of Rehearsal

Behavioral paradigm. A sequence of five consonant letters was presented on a screen, each for 750 msec separated by 250 msec interval. Subjects rehearsed the letters during an unfilled delay period ranging from 8 to 16 sec. Subsequently, five numbers were presented, each for 600 msec separated by 200 msec interval. Subjects had to add the numbers cumulatively. Then, after 200 msec, an arithmetic probe for the cumulative sum of the five numbers was presented for 800 msec, which the subjects had to confirm or disagree with by pressing a yes or no button. Then, after 1 sec, a memory probe followed, in which two letters were presented. The subjects judged whether the order of the two letters was the same as or different from the remembered sequence and responded by pressing the yes or no button. The four trial types (Mem–Dist, Mem–NoDist, NoMem–Dist, and NoMem–NoDist) were intermixed pseudorandomly and presented 15 trials each.