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Meyer, N. H.

Publications and source records attributed to Meyer, N. H..

2 recordsLinked to original sources

Embodiment in episodic memory through premotor-hippocampal coupling

Episodic memory (EM) allows us to remember and relieve past events and experiences, depending on cortical-hippocampal reinstatement involved during encoding. Although it has been claimed that EM is fundamental to establish a sense of self across time, this has never been shown experimentally. Here we combine immersive virtual reality and fMRI and report stronger hippocampal reinstatement for scenes encoded under preserved sense of self, reflecting later recall performance. We further link the sense of self to EM showing that hippocampal reinstatement is coupled with reinstatement in premotor cortex, a key sense of self region. We extend these findings in a severe amnesic patient (caused by bilateral hippocampal damage), whose memory and re-experiencing lacked the normal dependency on the sense of self. Premotor-hippocampal coupling in EM describes how the self at encoding is neurally reinstated during the retrieval of past episodes, enabling a sense of self across time. TeaserPremotor-hippocampal coupling reveals how the self is reinstated when retrieving past episodes.

neuroscience↗

Differential impact of brain network efficiency on post-stroke motor and attentional deficits

BackgroundMost studies on stroke have been designed to examine one deficit in isolation, yet survivors often have multiple deficits in different domains. While the mechanisms underlying multiple-domain deficits remain poorly understood, network-theoretical methods may open new avenues of understanding. Methods50 subacute stroke patients (7{+/-}3days post-stroke) underwent diffusion-weighted magnetic resonance imaging and a battery of clinical tests of motor and cognitive functions. We defined indices of impairment in strength, dexterity, and attention. We also computed imaging-based probabilistic tractography and whole brain connectomes. Overlaying individual lesion masks onto the tractograms enabled us to split the connectomes into their affected and unaffected parts and associate them to impairment. ResultsTo efficiently integrate inputs from different sources, brain networks rely on a "rich-club" of a few hub nodes. Lesions harm efficiency, particularly when they target the rich-club. We computed efficiency of the unaffected connectome, and found it was more strongly correlated to impairment in strength, dexterity and attention than efficiency of the total connectome. The magnitude of the correlation between efficiency and impairment followed the order attention > dexterity {approx} strength. Network weights associated with the rich-club were more strongly correlated to efficiency than non-rich-club weights. ConclusionsAttentional impairment is more sensitive to disruption of coordinated network activity between brain regions than motor impairment, which is sensitive to disruption of localized network activity. Providing more accurate reflections of actually functioning parts of the network enables the incorporation of information about the impact of brain lesions on connectomics contributing to a better understanding of underlying stroke mechanisms.

neuroscience↗