Cortical Hemodynamics and GABAergic Inhibition. Resting GABA Levels in Human Visual Cortex Correlate with BOLD, ASL-Measured CBF and VASO-Measured CBV Reactivity

Manus Joseph Donahue^1,2, Jamie Near^1,2, Peter Jezzard^1,2

Neurovascular coupling between neuronal activity, energy metabolism and cerebral blood flow (CBF) is supported by synaptic excitation and inhibition. We show inverse correlations between synaptic inhibition (GABA concentration) and BOLD (R=0.68) and cerebral blood volume (CBV)-weighted VASO reactivity (R=0.75) in human visual cortex. A negative correlation between baseline GABA and baseline CBV (R=0.75) is found; however, a positive relationship between GABA and ASL reactivity (R=0.38) and baseline CBF (R=0.67) is found, which we attribute to blood velocity discrepancies. Results provide information on the relationship between cortical activity, GABAergic inhibition, and multimodal fMRI contrast. First two authors are equal contributors.