Dynamic Theta Oscillation in Frontotemporal systems Process Object and Time in Working Memory

In working memory (WM), we need coordination of multiple brain regions to process different types of information, such as prefrontal cortex (PFC) and medial temporal lobe (MTL, including the hippocampus) involve in processing of object task and temporal task. In both tasks, however, it is unclear at which period PFC and MTL function in memory. We addressed this question by presenting object task memory and temporal task memory to eight subjects with stereotaxic electrodes implanted in PFC and MTL. The results showed significant increase in theta power in PFC during post-cue (proc) delay phase of temporal task compared to post-cue delay phase of object task. And compared with encoding and maintenance (encmain) phases of object task, theta power in MTL was significantly increased during encmian phases of temporal task. This result suggested that PFC and MTL have temporal specificity in processing object task and temporal task, and this specificity is mainly concentrated in theta frequency band.