Neural Activity in Human Hippocampal Formation Reveals the Spatial Context of Retrieved Memories

TLDR

Place cells fire when an animal occupies specific locations, supporting spatial navigation across species. The study asks whether location‑specific neural activity contributes to the spatiotemporal context of episodic memory encoding. Medial temporal lobe activity was recorded from epilepsy patients during a hybrid spatial‑episodic task, and place‑responsive cells identified during virtual navigation were examined for reactivation during memory recall without navigation. Place‑responsive cells reactivated during episodic recall, with firing patterns matching those that encoded the original spatial locations.

Abstract

In many species, spatial navigation is supported by a network of place cells that exhibit increased firing whenever an animal is in a certain region of an environment. Does this neural representation of location form part of the spatiotemporal context into which episodic memories are encoded? We recorded medial temporal lobe neuronal activity as epilepsy patients performed a hybrid spatial and episodic memory task. We identified place-responsive cells active during virtual navigation and then asked whether the same cells activated during the subsequent recall of navigation-related memories without actual navigation. Place-responsive cell activity was reinstated during episodic memory retrieval. Neuronal firing during the retrieval of each memory was similar to the activity that represented the locations in the environment where the memory was initially encoded.