tVNS Responsiveness Testing With Pupil Size
August 27, 2026 updated by: Georgia Institute of Technology
Movement-Associated tVNS and Responsiveness Testing for Personalized Rehabilitation
The goal of this study is to learn about the acute pupil response to transcutaneous vagus nerve stimulation (tVNS) in stroke survivors and healthy adults.
The main question it aims to answer is whether pupil size response is greater with bilateral tVNS compared to unilateral tVNS.
Participants will receive tVNS and sham at the outer ear unilaterally and bilaterally in resting condition.
The pupil size of the participants will be recorded during tVNS.
Study Overview
Status
Completed
Conditions
Detailed Description
Participants will wear surface electrodes on the outer ear on both sides and a finger device that monitors heart rate.
The attachment sites are the tragus or the cymba concha (depending on the shape and size of the ear) for tVNS and the ear lobe for sham.
The electrical current will have a pulse duration of 0.1 ms at 30 Hz with an intensity below the pain threshold or 5 milliamp, whichever is lower, for a duration of 0.5 s.
The experimental stimulation intensity will be determined as just below the pain threshold.
Participants will receive multiple blocks of unilateral left, unilateral right, and bilateral stimulations to the sham or tVNS electrodes at rest, during which their pupil size will be recorded.
The order of unilateral/bilateral and sham/tVNS stimulation will be randomized.
Study Type
Interventional
Enrollment (Actual)
21
Phase
- Not Applicable
Contacts and Locations
This section provides the contact details for those conducting the study, and information on where this study is being conducted.
Study Locations
-
-
Georgia
-
Atlanta, Georgia, United States, 30318
- Human Neuromuscular Physiology Lab
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-
Participation Criteria
Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.
Eligibility Criteria
Ages Eligible for Study
- Adult
- Older Adult
Accepts Healthy Volunteers
Yes
Description
Inclusion Criteria:
- 18-89 years old across all races, genders, and ethnicities.
- Post-stroke subjects will have persistent hemiparesis on the upper extremity (UE) with some residual UE voluntary movement.
Exclusion Criteria:
Able-bodied subjects:
- Younger than 18 years old or older than 89 years old
- Current or history of cardiac disease
- Have a vision problem not corrected by glasses or contact lenses
- Have an implanted device such as a neurostimulator or cochlear implant
- Current or history of tympanic membrane perforation
- Had a stroke or lesion (including tumor) in your brain
- Had a head injury or brain surgery
- Suffer from frequent or severe headaches
- Had a fainting spell or syncope
- Have any metal in the head such as shrapnel, surgical clips, or fragments from welding or metal work
- Have any implanted device such as cardiac pacemakers, medical pumps, or intra-cardiac lines
- Had any brain-related conditions (i.e. multiple sclerosis, Parkinson, Alzheimer)
- Had any illness that caused brain injury (i.e. meningitis, aneurysm, brain tumor)
- Had any head trauma that was associated with a loss of consciousness or diagnosed as a concussion
- Being treated for any psychiatric condition (i.e. depression, anxiety, PTSD, schizophrenia)
- Suspected of pregnancy
Post-stroke subjects:
- Younger than 18 years old or older than 89 years old
- Current or history of cardiac disease
- Have a vision problem not corrected by glasses or contact lenses
- Have any implanted devices such as a neurostimulator or cochlear implant
- Current or history of tympanic membrane perforation
- No persistent hemiparesis on the upper extremity (UE)
- No residual UE voluntary movement
- A first stroke less than 4 months prior to the participation
- Serious uncontrolled medical conditions
- Excessive pain in any joint of the more affected extremity
- Unable to stand independently for 2 min., transfer independently to and from the toilet or perform sit-to-stand
- Suffer from frequent or severe headaches
- Had a fainting spell or syncope
- Have any metal in the head such as shrapnel, surgical clips, or fragments from welding or metal work
- Have any implanted device such as cardiac pacemakers, medical pumps, or intra-cardiac lines
- Had any illness that caused brain injury (i.e. meningitis, aneurysm, brain tumor)
- Had any head trauma that was associated with a loss of consciousness or diagnosed as a concussion
- Being treated for any psychiatric condition (i.e. depression, anxiety, PTSD, schizophrenia)
- Suspected of pregnancy
- A score of less than 24 on the Folstein Mini-Mental State Examination
- Excessive frailty or lack of stamina (e.g., cannot attend to instructions, stay awake, engage in functional activities, etc.)
- Excessive pain in any joint of the more affected extremity that could limit ability to cooperate with the intervention
Study Plan
This section provides details of the study plan, including how the study is designed and what the study is measuring.
How is the study designed?
Design Details
- Primary Purpose: Basic Science
- Allocation: N/A
- Interventional Model: Single Group Assignment
- Masking: None (Open Label)
Arms and Interventions
Participant Group / Arm |
Intervention / Treatment |
|---|---|
|
Experimental: Repeated-Measures Stimulation Protocol
All participants receive all six stimulation conditions: unilateral left sham, unilateral right sham, bilateral sham, unilateral left transcutaneous vagus nerve stimulation (tVNS), unilateral right tVNS, and bilateral tVNS.
Each participant completes 12 blocks during a single testing session, with each block containing one trial of each of the six stimulation conditions.
Twelve blocks with different predefined orders of the six conditions were established before testing began.
For each participant, the order of the 12 predefined blocks is randomized.
Thus, each participant receives each of the six stimulation conditions once per block and 12 times in total.
|
Electrical stimulation to the cymba concha and tragus of the outer ear on the left side.
Electrical stimulation to the cymba concha and tragus of the outer ear on both sides.
Electrical stimulation to the earlobe of the outer ear on the left side.
Electrical stimulation to the earlobe of the outer ear on both sides.
Electrical stimulation to the cymba concha and tragus of the outer ear on the right side.
Electrical stimulation to the earlobe of the outer ear on the right side.
|
What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
|
Peak Percent Change in Pupil Diameter During Stimulation
Time Frame: During one study visit (within 1 day)
|
For each stimulation trial, pupil diameter is recorded continuously.
The outcome is the maximum percent change in pupil diameter during the stimulation period relative to the mean pupil diameter measured immediately before stimulation within the same trial.
|
During one study visit (within 1 day)
|
|
Mean Percent Change in Pupil Diameter During Stimulation
Time Frame: During one study visit (within 1 day)
|
For each stimulation trial, pupil diameter is recorded continuously.
The outcome is the mean percent change in pupil diameter during the stimulation period relative to the mean pupil diameter measured immediately before stimulation within the same trial.
|
During one study visit (within 1 day)
|
Collaborators and Investigators
This is where you will find people and organizations involved with this study.
Sponsor
Collaborators
Investigators
- Principal Investigator: Minoru Shinohara, Ph.D., Georgia Institute of Technology
Study record dates
These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.
Study Major Dates
Study Start (Actual)
November 14, 2024
Primary Completion (Actual)
October 27, 2025
Study Completion (Actual)
October 27, 2025
Study Registration Dates
First Submitted
March 15, 2024
First Submitted That Met QC Criteria
March 27, 2024
First Posted (Actual)
March 28, 2024
Study Record Updates
Last Update Posted (Actual)
September 14, 2026
Last Update Submitted That Met QC Criteria
August 27, 2026
Last Verified
March 1, 2025
More Information
Terms related to this study
Additional Relevant MeSH Terms
Other Study ID Numbers
- H24109
- 5P2CHD086844-09 (U.S. NIH Grant/Contract)
Plan for Individual participant data (IPD)
Plan to Share Individual Participant Data (IPD)?
YES
IPD Plan Description
De-identified individual participant data on pupil size change will be available to other researchers outside the primary research group.
IPD Sharing Time Frame
The data will become available after the publication of all papers from the study.
IPD Sharing Access Criteria
The scientific data will be made available by a data repository after approval.
IPD Sharing Supporting Information Type
- STUDY_PROTOCOL
- SAP
- ICF
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
No
Studies a U.S. FDA-regulated device product
No
product manufactured in and exported from the U.S.
No
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