Intracranial EEG Investigation of Long-Term memory: Coding of Associations in the Human Medial Temporal Lobe

The role of the hippocampus has been fairly established in memory processes, yet there is still much controversy around what functions it precisely performs. In this study we further explored this matter by using human intracranial electroencephalography (iEEG) in patients suffering from epilepsy, allowing us to dive deeper into this issue with high precision in both temporal and spatial domains. Our results showed hippocampal involvement both at encoding and retrieval, both for “single item processing” and for processing its associated context (before it was shown to the participants). Moreover, we found “hippocampal Gamma” to play a unique role related to associating an item with a scene, in addition to merely “encoding “the information. This suggests that different roles proposed for how the hippocampus contributes to memory formation and retrieval (including scene processing, item processing, pattern completion, etc.) may not necessarily be mutually exclusive and in fact, the hippocampus may fulfill them all, perhaps through different neuronal populations and in different time windows.