Forebrain Network Associated With Cardiovascular Control in Exercising Humans

Figure 1. Time course of changes in heart rate (HR) and mean arterial pressure (MAP) during repeated 30-s bouts of handgrip exercise performed at 35% of maximal voluntary contraction (MVC) strength in a representative individual. Notice the reproducible changes in HR and MAP with minimal changes in efferent sympathetic nerve activity.

Figure 2. Averaged time course of the heart rate (HR) (top panel) and cortical responses during repeated 30-s trials of 5% and 35% exercise. The imaging panels show the averaged activity at the left motor cortex (M1), right insula (IC), ventral medial prefrontal cortex (vMPFC) and posterior cingulate cortex (PCC). Activity within the vMPFC and PCC were reduced during the exercise. Differences between the 5% and 35% trials were observed in the HR response and vMPFC activity but not PCC activity. The bars representing standard errors are only shown at the end of the exercise for clarity. The red-orange and blue-white brain highlights represent the activation and deactivation clusters, respectively. (Reprinted from (3). Copyright © 2007 Elsevier. Used with permission.)

Figure 3. Summary of common regions associated with the handgrip exercise task. Data represent nine groups (n = 124) from four published articles (3,25,27,47) and two unpublished studies from our laboratory. These participants each performed repeated bouts (27,47–50) of moderate intensity (35%–40% maximal strength) handgrip tasks, each lasting 30s. Right panels: Cortical areas of decreased activation relative to baseline in response to short-duration, moderate intensity isometric handgrip exercise. Left panels: Cortical areas of increased activation relative to baseline in response to short-duration, moderate intensity isometric handgrip exercise. False Discovery Rate pN = 0.01; minimum volume (mm3) = 200. Analysis performed using GingerALE (Version 2.3.2; BrainMap) and Mango (Version 3.1.2; Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX) (48–50). dACC, dorsal anterior cingulate cortex; HC, hippocampus; IC, insula cortex; MC, motor cortex; MPFC, medial prefrontal cortex; PCC, posterior cingulate cortex; SC, sensory cortex; TH, thalamus. Images are in radiological presentation with right side of the brain (R) on left, and left side of the brain (L) on…

Figure 4. BOLD responses in the insula (Top Panel) as well as cingulate and ventral medial prefrontal cortex (vMPFC) during sub-motor threshold stimulation (SUB), motor threshold stimulation (MOT), 5% MVC volitional wrist flexion (VOL5%), and 35% MVC volitional handgrip exercise (VOL35%) versus rest. IC, insular cortex; ACC, anterior cingulate cortex; PCC, posterior cingulate cortex; MCC, middle cingulate cortex. SUB and Motor conditions were induced by Transcutaneous Electrical Stimulation (TENS). Volitional handgrip assessed by a magnetic resonance imaging-compatible bladder (inset) or force transducer device (see Figure 2). (Adapted from [47]. Copyright © 2011 Elsevier. Used with permission.)

Figure 5. Illustration of an approach to conduct simulated orthostatic stress using lower body negative pressure while removing body movement when used during magnetic resonance imaging studies. Medical antishock trousers are fitted to the participant inside the lower body negative pressure chamber. By venting the trousers either to atmospheric or intrachamber pressures, they can be filled or emptied against a background of constant lower body suction. In this manner, the cardiovascular stress of the simulated orthostatic stress can be applied in box-car experimental models with minimal body movement at the onset or offset of suction.

Figure 6. Schematic of proposed neurocircuitry associated with the rapid heart rate response at the exercise onset that includes the integration of ascending somatosensory information from the Type I and II afferents from the contracting muscle. See text for description. aIC, anterior IC; Amyg, amygdala; dACC, dorsal anterior cingulate cortex; DMN, dorsal motor nucleus; HC, hippocampus; MC, motor cortex; MPFC, medial prefrontal cortex; NA, nucleus ambiguous; NTS, nucleus tractus solitarius; pIC, posterior IC; RVLM, rostral ventrolateral medulla; represent key regions in this pathway in the context of rapid heart rate changes at the exercise onset.