Individual Differences in Stressor-Evoked Blood Pressure Reactivity Vary with Activation, Volume, and Functional Connectivity of the Amygdala

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Abstract
Individuals who exhibit exaggerated blood pressure reactions to psychological stressors are at risk for hypertension, ventricular hypertrophy, and premature atherosclerosis; however, the neural systems mediating exaggerated blood pressure reactivity and associated cardiovascular risk in humans remain poorly defined. Animal models indicate that the amygdala orchestrates stressor-evoked blood pressure reactions via reciprocal signaling with corticolimbic and brainstem cardiovascular-regulatory circuits. Based on these models, we used a multimodal neuroimaging approach to determine whether human individual differences in stressor-evoked blood pressure reactivity vary with amygdala activation, gray matter volume, and functional connectivity with corticolimbic and brainstem areas implicated in stressor processing and cardiovascular regulation. We monitored mean arterial pressure (MAP) and concurrent functional magnetic resonance imaging BOLD signal changes in healthy young individuals while they completed a Stroop color-word stressor task, validated previously in epidemiological studies of cardiovascular risk. Individuals exhibiting greater stressor-evoked MAP reactivity showed (1) greater amygdala activation, (2) lower amygdala gray matter volume, and (3) stronger positive functional connectivity between the amygdala and perigenual anterior cingulate cortex and brainstem pons. Individual differences in amygdala activation, gray matter volume, and functional connectivity with corticolimbic and brainstem circuits may partly underpin cardiovascular disease risk by impacting stressor-evoked blood pressure reactivity.