Functional MRI using blood oxygenation level dependent (BOLD) contrast identifies brain regions for task-induced (de)activation paradigms. We investigated the metabolic basis of these paradigms in activated (visual cortex, VC) and deactivated (posterior cingulate cortex, PCC) network nodes using concurrent acquisitions of J-edited lactate/GABA(γ-aminobutyric acid)/Glx(pooled glutamate and glutamine) and diffusion-weighted BOLD signal. In VC, we detected increased BOLD/lactate/glutamate, and decreased GABA, whereas in PCC BOLD decreased, GABA increased but lactate/glutamate did not change. These results suggest that BOLD responses in (de)activated areas is regulated by relatively rapid GABAergic inhibition, whereas aerobic glycolysis and glutamatergic activity dominate in activated nodes.
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