Abstract
Complex memory of personal events is thought to depend on coordinated reinstatement of cortical representations by the medial temporal lobes (MTL). MTL-cortical theta and gamma coupling is believed to mediate such coordination, but which cortical structures are critical for retrieval and how they influence oscillatory coupling is unclear. We used magnetoencephalography (MEG) combined with continuous theta burst stimulation (cTBS) to (i) clarify the roles of theta and gamma oscillations in network-wide communication during naturalistic memory retrieval, and (ii) understand the causal relationship between cortical network nodes and oscillatory communication. Retrieval was associated with MTL-posterior neocortical theta phase coupling and theta-gamma phase-amplitude coupling relative to a rest period. Precuneus cTBS altered MTL-neocortical communication by modulating theta and gamma oscillatory coupling. These findings provide a mechanistic account for MTL-cortical communication and demonstrate that the precuneus is a critical cortical node of oscillatory activity, coordinating cross-regional interactions that drive remembering.
Highlights
Detailed, complex memories of personal events can last a lifetime and be brought to mind at will
The present study revealed three main findings: (1) Recall of complex personal memories involves the precuneus as a critical cortical node; (2) Complex memory retrieval is supported by medial temporal lobes (MTL)-cortical communication mediated by theta phase coupling and theta-gamma phase-amplitude coupling (PAC); (3) Inhibitory precuneus stimulation leads to network-level alteration of MTL-driven oscillatory coupling, both with the precuneus itself and with other posterior cortical structures
We identified phase-amplitude coupling between MTL theta and precuneus gamma during memory elaboration compared to rest which was sensitive to vividness ratings, but did not find PAC between the MTL and medial prefrontal cortex (mPFC) or temporoparietal junction (TPJ)
Summary
Complex memories of personal events can last a lifetime and be brought to mind at will. There is little empirical evidence indicating which neocortical structures are crucially involved in the reinstatement of detailed personal memories. Causal evidence is lacking for a mechanistic account of how such coordinated reactivation occurs during complex personal memory retrieval. While previous studies have shown that MTL and medial parietal structures are associated with spatial aspects of personal memory retrieval (Freton et al, 2014; Hebscher et al, 2018; St Jacques et al, 2017), they are unable to determine whether these regions are critical for retrieval, or how they may communicate with one another to allow for information transfer
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