Episodic memory involves transient and sparse connectivity aligned to both internal and external events
Adam J. O. Dede, Zachariah R. Cross, Samantha M. Gray, Joseph P. Kelly, Qin Yin, Parisa Vahidi, Eishi Asano, Stephan U. Schuele, Joshua M. Rosenow, Joyce Y. Wu, Sandi K. Lam, Jeffrey S. Raskin, Jack J. Lin, Olivia Kim McManus, Shifteh Sattar, Ammar Shaikhouni
TL;DR
This study shows that episodic memory relies on short-lived, sparsely connected brain states that change between encoding and retrieval.
Contribution
The study reveals dynamic shifts in brain connectivity and timing between encoding and retrieval of episodic memories.
Findings
PFC-MTL theta connectivity is aligned with internal PFC peaks during encoding and external stimuli during retrieval.
Anterior cingulate cortex connectivity is aligned only with internal HFB peaks, indicating an evaluative role.
Successful memory performance is linked to transient, sparse whole-brain network states.
Abstract
Episodic memory depends on the coordination of local processing, indexed by high-frequency broadband (HFB) activity, with global organization, indexed by theta oscillations. However, theta and HFB exhibit asynchronous timing, raising the question of how results of local processing are communicated. Using intracranial EEG in patients performing a recognition memory task, we examined this coordination across medial temporal (MTL) and prefrontal (PFC) regions. HFB peaks occurred earlier in the MTL than in the PFC. Contrasting analyses were anchored either to these internally driven HFB peaks or to the external event of stimulus presentation. We discovered three key results. First, the role of the PFC changed from encoding to retrieval. Specifically, PFC-MTL theta connectivity was aligned with internal PFC peaks during encoding, suggesting top-down initiation. By contrast, this connection…
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Taxonomy
TopicsFunctional Brain Connectivity Studies · Neural and Behavioral Psychology Studies · Neural dynamics and brain function