Frontal theta activity in humans increases with memory load in a working memory task

TLDR

Recent theoretical work has suggested that brain oscillations in the theta band are involved in active maintenance and recall of working memory representations. The study aimed to test this framework by recording neuromagnetic responses from 10 subjects while they performed a Sternberg task. Subjects retained lists of 1, 3, 5, or 7 visually presented digits during a 3‑second retention period, with neuromagnetic activity recorded over frontal brain areas. Frontal theta activity (7–8.5 Hz) increased with memory load during the retention and scanning periods and diminished afterward, indicating an active role in memory maintenance.

Abstract

Abstract Recent theoretical work has suggested that brain oscillations in the theta band are involved in active maintenance and recall of working memory representations. To test this theoretical framework we recorded neuromagnetic responses from 10 subjects performing the Sternberg task. Subjects were required to retain a list of 1, 3, 5 or 7 visually presented digits during a 3‐s retention period. During the retention period we observed ongoing frontal theta activity in the 7–8.5‐Hz band recorded by sensors over frontal brain areas. The activity in the theta band increased parametrically with the number of items retained in working memory. A time–frequency analysis revealed that the task‐dependent theta was present during the retention period and during memory scanning. Following the memory task the theta activity was reduced. These results suggest that theta oscillations generated in frontal brain regions play an active role in memory maintenance.