Theta-gamma coupling during a working memory task as compared to a simple vigilance task.

Theta-gamma coupling (TGC) is known to reflect working memory processes, but it is unclear whether TGC as measured by scalp electroencephalography (EEG) reflects working memory processes or nonspecific attentional processes. In this study, we examined the degree of TGC during a visuo-spatial working memory task (2-back task) vs. a simple vigilance task in 13 young participants. During the working memory task, TGC increased in the frontal area at approximately 40 Hz. In addition, TGC was also significantly different at high-gamma frequency despite no differences in gamma power between the two tasks, and a correlation between TGC only during the working memory task and hit rate was observed. These results suggest that TGC reflects working memory processes and may be a useful bio-physiological marker of working memory.