Dissertations, Theses, and Capstone Projects

Date of Degree

9-2026

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy

Program

Psychology

Advisor

Marom Bikson

Committee Members

Jack Martin

Lucas Parra

Jacek Dmochowski

Subject Categories

Cognitive Neuroscience | Other Neuroscience and Neurobiology

Keywords

transcutaneous auricular vagus nerve stimulation, vagus nerve stimulation, autonomic nervous system, neuromodulation, cranial nerves, neurotechnology

Abstract

Cranial nerves provide afferent pathways that enable bottom-up modulation of central autonomic and cognitive neural pathways. Because these pathways project to brainstem nuclei such as the nucleus tractus solitarius and engage neuromodulatory systems, including the locus coeruleus, electrical stimulation offers a mechanistically grounded approach to influencing brain function. This thesis tested whether active transcutaneous auricular vagus nerve stimulation (taVNS) produces physiological responses indicative of parasympathetic engagement, defined as decreases in heart rate, increases in heart rate variability, and decreases in respiration relative to a dose-matched earlobe control condition. Using cardiac and respiratory measures as physiological markers, taVNS at the tragus was compared to an anatomically distinct earlobe control across multiple waveform conditions.

Heart rate variability (HRV) showed selective modulation: the 25 Hz waveform increased HRV during tragus stimulation relative to control, consistent with parasympathetic engagement, whereas other waveforms did not. Respiration and heart rate had no significant effects. These findings indicate that vagal pathway activation depends on stimulation parameters and identify HRV as a sensitive marker of vagal parasympathetic modulation.

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