Brain systems for baroreflex suppression during stress in humans

The arterial baroreflex is a key mechanism for the homeostatic control of blood pressure (BP). In animals and humans, psychological stressors suppress the capacity of the arterial baroreflex to control short-term fluctuations in BP, reflected by reduced baroreflex sensitivity (BRS). While animal studies have characterized the brain systems that link stressor processing to BRS suppression, comparable human studies are lacking. Here, we measured beat-to-beat BP and heart rate (HR) in 97 adults who performed a multisource interference task that evoked changes in spontaneous BRS, which were quantified by a validated sequence method. The same 97 participants also performed the task during functional magnetic resonance imaging (fMRI) of brain activity. Across participants, task performance (i) increased BP and HR and (ii) reduced BRS. Analyses of fMRI data further demonstrated that a greater task-evoked reduction in BRS covaried with greater activity in brain systems important for central autonomic and cardiovascular control, particularly the cingulate cortex, insula, amygdala, and midbrain periaqueductal gray (PAG). Moreover, task performance increased the functional connectivity of a discrete area of the anterior insula with both the cingulate cortex and amygdala. In parallel, this same insula area showed increased task-evoked functional connectivity with midbrain PAG and pons. These novel findings provide human evidence for the brain systems presumptively involved in suppressing baroreflex functionality, with relevance for understanding the neurobiological mechanisms of stressor-related cardiovascular reactivity and associated risk for essential hypertension and atherosclerotic heart disease.