HUMAN FRONTAL MIDLINE THETA AND ITS SYNCHRONIZATION TO GAMMA OSCILLATIONS DURING VERBAL WORKING MEMORY

The involvement of oscillatory activity, especially theta and gamma oscillations, in human working memory has been reported repetitively. Therefore, we investigated whether frontalmidline theta activity is linked to gamma oscillations during the performance of a verbal working memory task and whether it might be attributable to a specific cognitive process. The electroencephalogram was recorded from 15 subjects while they performed a delayedmatch to sample task with two different conditions (manipulation, retention). The results of the study indicated higher frontal midline theta activity for the manipulation compared to the retention condition. Moreover, cross-frequency phase synchronization between frontal midline theta activity and gamma activity was predominant during manipulation of verbal stimulus material compared to pure retention of verbal stimulus material. This effect was mainly apparent at frontal brain areas and was restricted to the first part of the delay period.We suppose that frontal midline theta:gamma coupling reflects some kind of updating process in the context of executive processes.