Vagus Nerve Stimulation
Conditions
Brief summary
This study aims to understand the role of the vagus nerve in promoting social bonding by using a non-invasive stimulation technique called transcutaneous vagal nerve stimulation (tVNS). The investigators will investigate whether tVNS can improve emotional, physiological, and behavioral experiences during and after social interactions. Couples will be randomly assigned to receive either tVNS or a sham stimulation during gratitude expression and problem-solving discussions. The investigators will measure their subjective evaluations of the interactions and capture their physiological and behavioral synchrony. This research will shed light on the processes involved in social connection and explore the potential of tVNS as a tool to enhance bonding in close relationships.
Detailed description
As fundamental as the need to belong is to human survival and functioning, decades of research have shown that social connection is critical to emotional well-being. The current investigation seeks to use the knowledge and technological advances in the biomedical field to examine the causal role of the vagus nerve in promoting social bonding. Specifically, building on the recent evidence suggesting the effects of transcutaneous vagal nerve stimulation (tVNS) on improving social cognitive functioning, this study will examine the utility of tVNS in modulating emotional, physiological, and behavioral experiences during and after social interactions. The investigators will examine if romantic couple assigned to receive tVNS vs. active sham stimulation during two types of conversations (i.e., gratitude expression and problem-solving discussion) show differences in their experiences of the interactions. The study outcomes will include subjective evaluations of the interaction (e.g., felt emotions) and their physiological synchrony. This investigation will provide insights into the mechanistic processes that undergird social connection and, importantly, be the first to examine the potential utility of tVNS as an intervention tool for promoting social bonding within close relationships.
Interventions
The intervention consists of neurostimulation device that is programmed to a stimulus intensity at 0.5mA with a stimulation frequency of 25 Hz at the outer auditory canal.
Sponsors
National Institute on Aging (NIA)
University of California, San Francisco
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Masking description
Participant couples will be blinded to their condition. Experimenters running the study will not be blinded since tVNS administration currently requires their knowledge of the condition.
Intervention model description
Couple dyads will be randomly assigned to receive either tVNS or sham stimulation.
Eligibility
Sex/Gender
ALL
Age
18 Years to 39 Years
Healthy volunteers
Yes
Inclusion criteria
* Fluent in English * Having been in a relationship with the partner for at least a year * Within the age range of 18-39
Exclusion criteria
* Major chronic disease. self-reported autoimmune disease; severe asthma; lung disease (such as chronic bronchitis; history of stroke, heart attack, epilepsy, brain injury); cardiovascular disease. * Cancer: if not in remission. * Substance dependence-current or long history (5 years of more). * Current psychiatric diagnosis that is not being treated with medication * Confounding medications, including those used to treat hypertension and cardiovascular conditions; psychoactive substances; and medications known to directly affect autonomic functioning.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Self-reported Positive Affect | Once, self-reported in a survey immediately following conflict interaction, up to 10 minutes | During the conversation, overall, I felt… (1: not at all positive, 7: extremely positive) |
| Self-reported Negative Affect | Once, self-reported in a survey immediately following conflict interaction, up to 10 minutes | During the conversation, overall, I felt… (1: not at all negative, 7: extremely negative) |
| Respiratory Sinus Arrhythmia | Continuously throughout conflict conversation | RSA was assessed continuously throughout the conversation. |
| Interbeat Interval | Continuously throughout the conflict conversation | IBI was assessed continuously throughout the conversation. |
Countries
United States
Participant flow
Recruitment details
A total of 80 couples (i.e., 160 participants) were recruited from February 2024.
Pre-assignment details
Couples were randomly assigned to either the active or sham stimulation condition after confirming their eligibility and completing a background questionnaire at home. Although all sessions were completed, technical issues (e.g., tVNS device malfunction) occurred in some cases. When this happened, the affected couple was excluded from the random assignment, and the next couple was reassigned to that condition.
Participants by arm
| Arm | Count |
|---|---|
| Active tVNS We delivered stimulation at the individually calibrated intensity continuously during the interactions, and the default device settings we adopted were as follows: frequency = 30Hz, phase duration = 250μs, interphase interval = 50μs, and max voltage = 65V. In the active stimulation condition, both partners will have the stimulation clip attached to the outer auditory canal. | 63 |
| Sham tVNS In the sham condition, both partners will have electrodes attached to the center of the left ear lobe. They will still receive stimulation but at a placement that should not activate the vagus nerve. | 71 |
| Total | 134 |
Baseline characteristics
| Characteristic | Active tVNS | Sham tVNS | Total |
|---|---|---|---|
| Age, Continuous | 28.17 years STANDARD_DEVIATION 4.33 | 27.65 years STANDARD_DEVIATION 4.26 | 27.90 years STANDARD_DEVIATION 4.29 |
| Race (NIH/OMB) American Indian or Alaska Native | 1 Participants | 2 Participants | 3 Participants |
| Race (NIH/OMB) Asian | 27 Participants | 35 Participants | 62 Participants |
| Race (NIH/OMB) Black or African American | 0 Participants | 3 Participants | 3 Participants |
| Race (NIH/OMB) More than one race | 1 Participants | 4 Participants | 5 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 1 Participants | 4 Participants | 5 Participants |
| Race (NIH/OMB) White | 33 Participants | 23 Participants | 56 Participants |
| Relationship duration | 4.23 Years STANDARD_DEVIATION 3.06 | 4.41 Years STANDARD_DEVIATION 2.41 | 4.33 Years STANDARD_DEVIATION 2.73 |
| Sex/Gender, Customized Female/Male/Other Female | 30 Participants | 34 Participants | 64 Participants |
| Sex/Gender, Customized Female/Male/Other Male | 32 Participants | 34 Participants | 66 Participants |
| Sex/Gender, Customized Female/Male/Other Other | 1 Participants | 3 Participants | 4 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | 0 / 0 | 0 / 0 |
| other Total, other adverse events | 0 / 160 | 0 / 160 |
| serious Total, serious adverse events | 0 / 0 | 0 / 0 |
Outcome results
Primary
Interbeat Interval
IBI was assessed continuously throughout the conversation.
Time frame: Continuously throughout the conflict conversation
Population: Our analysis included 134 participants with complete physiological and self-report data. Missing data resulted from session failures (e.g., unstable or missing physiological measurements) or survey non-response
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Active tVNS | Interbeat Interval | 793.71 ms | Standard Deviation 101.74 |
| Sham tVNS | Interbeat Interval | 808.20 ms | Standard Deviation 100.63 |
Primary
Respiratory Sinus Arrhythmia
RSA was assessed continuously throughout the conversation.
Time frame: Continuously throughout conflict conversation
Population: Our analysis included 134 participants with complete physiological and self-report data. Missing data resulted from session failures (e.g., unstable or missing physiological measurements) or survey non-response
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Active tVNS | Respiratory Sinus Arrhythmia | 6.47 ms | Standard Error 0.74 |
| Sham tVNS | Respiratory Sinus Arrhythmia | 6.54 ms | Standard Error 0.89 |
Primary
Self-reported Negative Affect
During the conversation, overall, I felt… (1: not at all negative, 7: extremely negative)
Time frame: Once, self-reported in a survey immediately following conflict interaction, up to 10 minutes
Population: Our analysis included 134 participants with complete physiological and self-report data. Missing data resulted from session failures (e.g., unstable or missing physiological measurements) or survey non-response
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Active tVNS | Self-reported Negative Affect | 5.79 units on a scale | Standard Deviation 1.18 |
| Sham tVNS | Self-reported Negative Affect | 5.62 units on a scale | Standard Deviation 1.32 |
Primary
Self-reported Positive Affect
During the conversation, overall, I felt… (1: not at all positive, 7: extremely positive)
Time frame: Once, self-reported in a survey immediately following conflict interaction, up to 10 minutes
Population: Our analysis included 134 participants with complete physiological and self-report data. Missing data resulted from session failures (e.g., unstable or missing physiological measurements) or survey non-response
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Active tVNS | Self-reported Positive Affect | 5.89 units on a scale | Standard Deviation 0.92 |
| Sham tVNS | Self-reported Positive Affect | 5.69 units on a scale | Standard Deviation 1.15 |