Causal Relationships Underlying Episodic Memory Network Dynamics in Older Adults

BioRxiv : the Preprint Server for Biology
Simon W DavisRoberto Cabeza

Abstract

The most reliable finding in functional neuroimaging studies of cognitive aging is a more widespread brain activity pattern in older than younger adults. The additional regions recruited by older adults are functionally connected to core task-network regions, and frequently contribute to task performance in this group, suggesting that older adults may compensate for core task-network deficits by expanding the task-related network. This hypothesis is difficult to resolve with functional neuroimaging alone, because it is unclear both how to define reliable causal trends in which connections are important (e.g., local versus indirect connections). To address this problem we examined functional connectivity measures as quantified by a region's local within-module degree (WMD), or their between-module degree (BMD) between distant cortical communities. We combined these graph theoretical measures with diffusion tensor imaging (DTI) and repetitive transcranial magnetic stimulation (rTMS) in order to resolve the central hypothesis. We applied enhancing (5Hz) or impairing (1Hz) rTMS to a core episodic encoding region, the left prefrontal cortex (PFC) and predicted that (1) if older adults compensate for local deficits by boosting BMD, t...Continue Reading

Related Concepts

Prefrontal Cortex
Functional Neuroimaging
Diffusion Weighted Imaging
Neurons
Brain
Memory, Episodic
Structure of Cortex of Kidney
Transcranial Magnetic Stimulation, Repetitive
FMRI
Left Prefrontal Cortex

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