Hippocampal ripples signal contextually mediated episodic recall
Abstract
High-frequency oscillatory events, termed ripples, represent synchrony of neural activity in the brain. Recent evidence suggests that medial temporal lobe (MTL) ripples support memory retrieval. However, it is unclear if ripples signal the reinstatement of episodic memories. Analyzing electrophysiological MTL recordings from 245 neurosurgical participants performing episodic recall tasks, we find that the rate of hippocampal ripples rises just prior to the free recall of recently formed memories. This prerecall ripple effect (PRE) is stronger in the CA1 and CA3/dentate gyrus (CA3/DG) subfields of the hippocampus than the neighboring MTL regions entorhinal and parahippocampal cortex. PRE is also stronger prior to the retrieval of temporally and semantically clustered, as compared with unclustered, recalls, indicating the involvement of ripples in contextual reinstatement, which is a hallmark of episodic memory.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 26, 2022
- Source ID
- 10.1073/pnas.2201657119
Entities
People
- John J Sakon
- Michael J. Kahana
Organizations
- National Institute of Neurological Disorders and Stroke
- University of Pennsylvania