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

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

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

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
21

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • 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 Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • United States
    • Georgia
      • Atlanta, Georgia, United States, 30318
        • Human Neuromuscular Physiology Lab

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

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

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
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.
Procedure: Unilateral Left tVNS stimulation
Electrical stimulation to the cymba concha and tragus of the outer ear on the left side.
Procedure: Bilateral tVNS stimulation
Electrical stimulation to the cymba concha and tragus of the outer ear on both sides.
Procedure: Unilateral Left Sham stimulation
Electrical stimulation to the earlobe of the outer ear on the left side.
Procedure: Bilateral Sham stimulation
Electrical stimulation to the earlobe of the outer ear on both sides.
Procedure: Unilateral Right tVNS stimulation
Electrical stimulation to the cymba concha and tragus of the outer ear on the right side.
Procedure: Unilateral Right Sham stimulation
Electrical stimulation to the earlobe of the outer ear on the right side.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
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

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Georgia Institute of Technology

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
Emory University

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • 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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
November 14, 2024

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
October 27, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
October 27, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
March 15, 2024

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
March 27, 2024

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
March 28, 2024

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 14, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 27, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
March 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant 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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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