Abstract Details

Title Interactions of Resting State Brain Networks, Dopamine, and Working Memory Behavior: A Resting State Functional MRI Study

Topic Behavioral Neurology

Presentation(s) S54 - (-)

Poster/Presentation
Number 003

Objective

Background Resting state brain networks have a modular structure that is thought to reflect global and local efficiency of parallel information processing, and emerging evidence suggests that properties of these networks are correlated with cognitive processing. The dopamine neurotransmitter system plays an important role in complex cognitive functions such as working memory. We hypothesized that functional brain network organization in humans would be modulated after administration of a dopaminergic agonist, and that the magnitude of network reorganization would capture changes in individual variation of working memory performance.

Design/Methods We collected resting-state functional MRI (rs-fMRI) data and behavior on a working memory task in healthy young adults following the administration of bromocriptine, a dopamine agonist, or placebo in a randomized, double-blind procedure. Pairwise correlations of blood-oxygen dependent signal time series between atlas regions were used to create a correlation matrix for each subject. Matrices were thresholded to create undirected, unweighted graphs, which were partitioned into modules by optimizing Newman's modularity, a measure of the density of intra- versus inter-modular connections. Behavioral variability was measured as the inter-individual coefficient of variation of reaction time.

Results Modularity in either the drug or placebo session showed no relationship with RT variability in the same session. However, drug-induced decreases in modularity were correlated with drug-induced increases in RT variability. Furthermore, greater modularity in the placebo session predicted greater drug-induced RT variability.

Conclusions Our findings are consistent with a role of dopamine in modulating the large-scale organization of brain networks. Moreover, they suggest that individual differences in baseline brain organization may be an important factor in determining the effects of dopamine on behavior.

Authors/Disclosures
Robert White, MD, PhD (Washington University) PRESENTER	No disclosure on file
	No disclosure on file
Mark T. D'Esposito, MD, FAAN (University of California)	No disclosure on file
Josemir W. Sander, MD, PhD (UCL Queen Square Institute of Neurology)	No disclosure on file

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