Quantitative Time-Series Analysis of Sympathetic Responses Across Laboratory-Induced Stressors

Long term, chronic exposure to stress and elevated sympathetic nervous system activation has been correlated with hypertension and associated comorbidities such as obesity, heart failure, and stroke. While central autonomic measures of sympathetic activation such as heart rate variability (HRV) and blood pressure (BP) have been reported, there is a lack of detailed time-series assessment of how broader sets of cardiovascular features are modulated across different laboratory-induced stressors in peripheral sympathetic signals. We hypothesize that there exist features in both electrodermal activity (EDA) and photoplethysmography (PPG) indicative of both transient and sustained active stressors. Healthy adult male and female human participants (n = 15) were recruited and presented with laboratory-induced stressors in the form of either a single-pulse electrocutaneous stimulation over the median nerve, an auditory startle, or a Stroop Interference task. All participants were instrumented with sensors for recording a Lead II electrocardiogram (ECG), photoplethysmogram (PPG), or electrodermal activity (EDA). Additionally, beat-by-beat mean arterial pressure (MAP), heart rate (HR) and respiratory rate (RR) were recorded from the middle finger of the left hand (VitalStream, Caretaker Medical). Electrocutaneous stimulation was delivered using single cathodal pulses (30 mA and 200 µs pulse width), while auditory startle was evoked using 500 millisecond pure tones at 95 dB intensity. Finally, for mental stressors, the Stroop interference task was performed for a period of 2 minutes followed by 2 minutes of controlled breathing. Our results indicate that there is an initial “startle-like” response in peripheral EDA and PPG across all stressor modalities. Across these laboratory-induced stressors, there was a clear delineation in response magnitude between baseline and stressor periods. While electrocutaneous stimulation and auditory startle conditions induced peak evoked response magnitudes in EDA and PPG on the order of 5-10 seconds, Stroop interference induced sustained evoked magnitudes above baseline for EDA over the entire stressor block. Finally, our results show temporal and spectral features dependent on the given laboratory-induced stressor modality. In addition, these signals demonstrated fixed temporal relationships with one another. In-depth understanding of the effects of individual variability, external psychosocial factors, and habituation on these features could be leveraged to motivate new diagnostic or evaluative metrics of stress in the future. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.