The Impact of Improved Vagal Function on Periaqueductal Gray Connectivity

Functional magnetic resonance imaging (fMRI) will be performed to measure activation of the PAG region during the looming task

Functional magnetic resonance imaging (fMRI) will be performed to measure activation of the PAG region while at rest

HRV will be measured using an ear clip and/or wristband and results will be recorded automatically in the app

The Fatigue Severity Scale (FSS) is a method of evaluating the impact of fatigue by asking participants to answer 9 statements that rate the severity of their fatigue symptoms in the past week by selecting their answer on a 1-7 point Likert scale. Sum scores range from 9-36. A low value (e.g., 1) indicates strong disagreement with the statement (lower symptom severity), whereas a high value (e.g., 7) indicates strong agreement (higher symptom severity).

The Generalized Anxiety Disorder Scale (GAD-2) is a method of evaluating anxiety symptoms by asking participants to answer 2 statements that rate the severity of their anxiety symptoms in the past 2 weeks by selecting their answer a 0-3 point Likert scale (0- not at all, 1- several days, 2 - more than half the days, 3 - nearly every day). Sum scores range from 0-6. A low value (e.g., 0) indicates no or less severe anxiety symptoms, whereas a high value (e.g. 3), indicates more severe anxiety symptoms.

The Adverse Childhood Experiences (ACE) questionnaire is a method of evaluating childhood adversities such as emotional, physical, and sexual abuse/neglect by asking participants to answer 10 statements that describe events that happened during the first 18 years of their life. Participants indicate if this event occurred by selecting a Yes or No answer. Sum scores range from 0-10. Less "Yes" responses indicate less ACE occurrences, and more "Yes" responses indicate more ACE occurrences.

The Pain Catastrophizing Scale (PCS) is a method of evaluating pain catastrophizing, measuring pain-related cognitions and the dimensions of helplessness, rumination and magnification by asking participants to answer 13 items that describe different thoughts and feelings that may be associated with their pain. Participants rate how strong their feelings are about pain on a 5 point scale (0- Not at all, 1- To a slight degree, 2- To a moderate degree, 3- To a great degree, 4- All the time). Sum scores range from 0-52. Higher scores indicate higher levels of pain catastrophizing. A total PCS score of 30 represents a clinically relevant level of catastrophizing.

The Patient Health Questionnaire (PHQ-9) objectifies and assesses degree of depression severity via questionnaire by asking participants to answer 9 items that rate the severity of depression symptoms over the past 2 weeks on a 0-3 point Likert scale (0- not at all, 1- several days, 2 - more than half the days, 3 - nearly every day). Sum scores range from 0-36. A low value (e.g., 0) indicates no or less severe depression symptoms, whereas a high value (e.g. 3), indicates more severe depression symptoms.

The Pittsburgh Sleep Quality Index (PSQI) measures quality and patterns of sleep in adults. It differentiates "poor" from "good" sleep quality by measuring seven areas (components): subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medications, and daytime dysfunction over the past month. Participants are asked to answer 19 items. 5 items are free response and ask questions about sleep duration. The remaining 14 items are answered on a 0-3 point Likert scale (0 - not during the past month, 1- less than once a week, 2- once or twice a week, 3- three or more times a week) that describe the frequency of the listed events. A global score is calculated from the sum of 7 component scores and ranges from 0-21, with lower scores indicating lower sleep dysfunction and higher scores indicating higher sleep dysfunction.

The PROMIS Physical Function (PROMIS 8b) instrument measures self-reported capability of physical activities by asking participants to respond to 8 items on a 5-point Likert scale. The scale for the first 4 items is as follows: 5- Without any difficulty, 4- With a little difficulty, 3- With some difficulty, 2- With much difficulty, 1- Unable to do. The scale for the last 4 items is as follows: 5- Not at all, 4- Very little, 3- Somewhat, 2- Quite a lot, 1- Cannot do. Raw sum scores range from 8-40 and are converted into a T-score ranging from 20.3 to 60.1, with higher scores indicating better physical function and lower scores indicating poorer physical function.

The Perceived Stress Scale (PSS) measures how different situations affect feelings and perceived stress. Participants are asked to answer 10 items that describe the frequency of their feelings and thoughts described in each item during the last month on a 0-4 point Likert scale (0 - never, 1- almost never, 2- sometimes, 3- fairly often, 4- very often). Sum scores range from 0-40, with lower scores indicating less perceived stress levels and higher scores indicating higher perceived stress levels.

The PCL-5 assesses the 20 DSM-5 symptoms of PTSD. Participants are asked to answer 5 free response questions about the worst & more stressful event to which they were exposed, then 20 items about the event on a 0-4 point Likert scale (0- not at all, 1- a little bit, 2- moderately, 3- quite a bit, 4- extremely). Sum scores of the 20 Likert-format items range from 0-80, with lower scores indicating less severe PTSD symptoms and higher scores indicating more severe PTSD symptoms.

The Pain, Enjoyment of Life, and General Activity (PEG-3) scale assesses pain levels and interference with enjoyment of life and activity. Participants are asked to answer 3 items on a 0-10 point Likert scale. For item 1, the scale is as follows: 0- no pain, 10- pain as bad as you can imagine. For items 2-3, the scale is as follows: 0- does not interfere, 10- completely interferes. Sum scores range from 0-30, with lower scores indicating less pain and/or interference and higher scores indicating more pain and/or interference.