1. Hippocampal ripples and their coordinated dialogue with the default mode network during recent and remote recollection
- Author
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Josef Parvizi, Yitzhak Norman, Omri Raccah, Su Liu, and Rafael Malach
- Subjects
Adult ,Male ,Neocortex ,Recall ,Autobiographical memory ,General Neuroscience ,Memory, Episodic ,Hippocampus ,Hippocampal formation ,Brain Waves ,Semantics ,medicine.anatomical_structure ,Mental Recall ,medicine ,Semantic memory ,Humans ,Female ,Psychology ,Neuroscience ,Episodic memory ,Default mode network - Abstract
Hippocampal ripples are prominent synchronization events generated by hippocampal neuronal assemblies. To date, ripples have been primarily associated with navigational memory in rodents and short-term episodic recollections in humans. Here, we uncover different profiles of ripple activity in the human hippocampus during the retrieval of recent and remote autobiographical events and semantic facts. We found that the ripple rate increased significantly before reported recall compared to control conditions. Patterns of ripple activity across multiple hippocampal sites demonstrated remarkable specificity for memory type. Intriguingly, these ripple patterns revealed a semantization dimension, in which patterns associated with autobiographical contents become similar to those of semantic memory as a function of memory age. Finally, widely distributed sites across the neocortex exhibited ripple-coupled activations during recollection, with the strongest activation found within the default mode network. Our results thus reveal a key role for hippocampal ripples in orchestrating hippocampal-cortical communication across large-scale networks involved in conscious recollection.
- Published
- 2021