Timing of goal match enhancement in the hippocampus revealed by human intracranial recording

Abstract

Hippocampus is involved in the memory encoding and retrieval, and its ability is influenced by the incoming events which match or mismatch the stored representation. Previous fMRI studies have reported that goal match enhancement, a component of working memory involving object identity and location, significantly activates the posterior hippocampus. However, information regarding the timing of this process is limited. In the current study, facilitated by the high spatial and temporal resolution of intracranial recording from human patients, we confirmed that the left posterior hippocampus plays an important role in the goal match enhancement effect. We also found that this effect occurs within 600 to 650 milliseconds of probe onset, about 200 ms later than perceptual effects such as the physical match enhancement effect or the P300. More specifically, within individuals, goal match enhancement latency is positively correlated with mean reaction time. The results suggest that the hippocampus plays an important role in working memory in tasks involving feature-location binding. The results further suggest that goal match enhancement effects occur after perceptual processes, implying a dissociation of different working memory components in the hippocampus.