Neocortico-hippocampal ripple-based coordination during naturalistic encoding

Abstract

AbstractMemory formation relies on effective communication between the hippocampus and neocortical areas. Ripples have been proposed as a key neural signature facilitating information transmission in the brain. However, their role in human memory encoding during naturalistic scenarios remains unexplored. Here, we recorded intracranial electrophysiological data from ten epilepsy patients watching a movie. Ripples were analyzed in the hippocampus and in neocortical regions (i.e., temporal and frontal cortex). Our results revealed a coordinated neocortico-hippocampal ripple-based interaction during encoding. However, this interaction exhibited distinct timing patterns: ripples in the temporal cortex preceded those from the hippocampus which then preceded those from frontal cortex. Additionally, enhanced hippocampal ripple recruitment was observed at event boundaries, reflecting hippocampal involvement in event segmentation. These findings shed light on the neural mechanisms underlying memory encoding and provide insights into the role of ripples in event segmentation, suggesting their potential role in forming long-term memories of distinct episodes.