Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Kinesiology

Supervisor

Shoemaker, Kevin

Abstract

Prefrontal cortical regions play an essential role in generating appropriate cardiovascular adjustments, particularly in cardio-vagally mediated heart rate (HR) responses to active tasks. Functional imaging studies provide correlational evidence that this region coordinates HR responses to exercise, however, direct experimental evidence of prefrontal cortical HR regulation in humans is not available. Seven persons with epilepsy implanted with intracranial electroencephalography (iEEG) completed 2-second isometric handgrip (IHG) contractions at no-stimulation (NO-STIM) or sham-stimulation (SHAM) conditions, and during direct electrical stimulation (STIM) of the orbitofrontal and medial prefrontal cortex. HR responses to IHG during NO-STIM and SHAM increased HR by Δ4.9±2.7 bpm, compared to an attenuated HR response of Δ1.7±3.1 bpm during STIM (P = 0.024). Using a novel electrical stimulation model, these preliminary data support the role of prefrontal cortices as a key node in the transient cardio-vagal response to IHG task, and are in agreement with previous neuroimaging and animal literature.

Summary for Lay Audience

Changes to our hearts rate are modified on a beat to beat basis, by a branch of the nervous system that operates involuntarily – called the autonomic nervous system. Through this system, signals arriving at the heart can increase or decrease heart rate when necessary. For example, your heart rate might increase if you encounter a grizzly bear in the wild or if you have to deliver a presentation in front of a large crowd. On the contrary, laying down on the couch after a big meal may decrease your heart rate. Higher regions of your brain have been shown to influence changes in heart rate, but this “brain-heart” relationship is poorly understood in the context of health and disease. This dissertation provides new information on the ability of higher brain regions to modify heart rate. We showed that modifying activity in this region of the brain via direct electrical stimulation reduced the ability of heart rate to rapidly increase during exercise. This mode of study was possible thanks to volunteering persons with epilepsy with clinically indicated brain electrode implants.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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