Theta Oscillations Support Prefrontal-hippocampal Interactions in Sequential Working Memory

The prefrontal cortex and hippocampus may support sequential working memory beyond episodic memory and spatial navigation. This stereoelectroencephalography (SEEG) study investigated how the dorsolateral prefrontal cortex (DLPFC) interacts with the hippocampus in the online processing of sequential information. Twenty patients with epilepsy (eight women, age 27.6 +/- 8.2 years) completed a line ordering task with SEEG recordings over the DLPFC and the hippocampus. Participants showed longer thinking times and more recall errors when asked to arrange random lines clockwise (random trials) than to maintain ordered lines (ordered trials) before recalling the orientation of a particular line. First, the ordering-related increase in thinking time and recall error was associated with a transient theta power increase in the hippocampus and a sustained theta power increase in the DLPFC (3-10 Hz). In particular, the hippocampal theta power increase correlated with the memory precision of line orientation. Second, theta phase coherences between the DLPFC and hippocampus were enhanced for ordering, especially for more precisely memorized lines. Third, the theta band DLPFC -> hippocampus influence was selectively enhanced for ordering, especially for more precisely memorized lines. This study suggests that theta oscillations may support DLPFC-hippocampal interactions in the online processing of sequential information.

Automated summary

This study investigated the interaction between the dorsolateral prefrontal cortex (DLPFC) and the hippocampus in the online processing of sequential information using stereoelectroencephalography (SEEG). The results showed that increases in thinking time and recall errors were associated with theta power increases in the hippocampus and the DLPFC. Theta phase coherences between the DLPFC and hippocampus were enhanced for ordering, and the DLPFC->hippocampus influence in the theta band was selectively enhanced for more precisely memorized lines. This suggests that theta oscillations may play a role in supporting the interaction between the DLPFC and hippocampus during the online processing of sequential information.