Theta reset, in which the rhythmic firing of neurons stops and then restarts to the onset of a stimulus, is believed to improve encoding and retrieval of stimuli by causing stimuli to be time-locked to waves of depolarization in the HPC. Recent research by Williams et al. (in preparation) has demonstrated that, in rats, theta reset occurs 1) in several cortical areas including the anterior cingulate (AC), 2) occurs during different phases of a working memory task for different cortical areas, and 3) can be predictive of working memory task performance. In the current study, human participants received EEG recording of the AC while performing a working memory task. Participants viewed a picture of a random dot arrangement for four seconds (encoding), viewed a blank screen for eight seconds in which the dots disappeared (delay), and viewed a second picture that was either the same or slightly different from the previous picture (retrieval). Participants decided if the second picture was the same or different and then made a choice on a response box. While no significant main effects were revealed, several trends were present. Greater theta reset occurred during the encoding phase of the task for participants who were high in overall accuracy than those who were low in accuracy for midline recording. In contrast, greater theta reset occurred during the retrieval phase for those who were low in accuracy than those who were high in accuracy for midline recording. Greater theta reset occurred in the retrieval phase of the task for both left and right AC recording. It is possible that increased focus on encoding stimuli, visible by an increase in theta reset, caused better encoding and, consequently, better accuracy for these participants. Lower accuracy may have resulted from misplaced focus on the retrieval stimulus (as evidenced by an increase in theta reset) instead of the encoding stimulus. This study provides insight into the role of theta reset in the memory functioning of the AC of humans.
Smith '03, Stephen W., "The Role of Prefrontal Theta Reset in Learning and Memory" (2003). Honors Projects. Paper 34.