tVNS Responsiveness Testing With Pupil Size

NCT ID: NCT06335199

Last Updated: 2025-10-29

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

21 participants

Study Classification

INTERVENTIONAL

Study Start Date

2024-11-14

Study Completion Date

2025-10-27

Brief Summary

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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.

Detailed Description

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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 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.

Conditions

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Stroke

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

SINGLE_GROUP

Primary Study Purpose

BASIC_SCIENCE

Blinding Strategy

DOUBLE

Participants Outcome Assessors

Study Groups

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Unilateral Left tVNS

Electrical stimulation to the vagus nerve area of the outer ear on the left side.

Group Type EXPERIMENTAL

Unilateral Left tVNS stimulation

Intervention Type PROCEDURE

Electrical stimulation to the cymba concha or tragus (depending on the ear dimension) of the outer ear on the left side after successful trials.

Bilateral tVNS

Electrical stimulation to the vagus nerve area of the outer ear on both sides.

Group Type EXPERIMENTAL

Bilateral tVNS stimulation

Intervention Type PROCEDURE

Electrical stimulation to the cymba concha or tragus (depending on the ear dimension) of the outer ear on both sides after successful trials.

Unilateral Left Sham

Electrical stimulation to the non-vagus nerve area of the outer ear on the left side.

Group Type SHAM_COMPARATOR

Unilateral Left Sham stimulation

Intervention Type PROCEDURE

Electrical stimulation to the earlobe of the outer ear on the left side after successful trials.

Bilateral Sham

Electrical stimulation to the non-vagus nerve area of the outer ear on both sides.

Group Type SHAM_COMPARATOR

Bilateral Sham stimulation

Intervention Type PROCEDURE

Electrical stimulation to the earlobe of the outer ear on both sides after successful trials.

Unilateral Right tVNS

Electrical stimulation to the vagus nerve area of the outer ear on the right side.

Group Type EXPERIMENTAL

Unilateral Right tVNS stimulation

Intervention Type PROCEDURE

Electrical stimulation to the cymba concha or tragus (depending on the ear dimension) of the outer ear on the right side after successful trials.

Unilateral Right Sham

Electrical stimulation to the non-vagus nerve area of the outer ear on the right side.

Group Type SHAM_COMPARATOR

Unilateral Right Sham stimulation

Intervention Type PROCEDURE

Electrical stimulation to the earlobe of the outer ear on the right side after successful trials.

Interventions

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Unilateral Left tVNS stimulation

Electrical stimulation to the cymba concha or tragus (depending on the ear dimension) of the outer ear on the left side after successful trials.

Intervention Type PROCEDURE

Bilateral tVNS stimulation

Electrical stimulation to the cymba concha or tragus (depending on the ear dimension) of the outer ear on both sides after successful trials.

Intervention Type PROCEDURE

Unilateral Left Sham stimulation

Electrical stimulation to the earlobe of the outer ear on the left side after successful trials.

Intervention Type PROCEDURE

Bilateral Sham stimulation

Electrical stimulation to the earlobe of the outer ear on both sides after successful trials.

Intervention Type PROCEDURE

Unilateral Right tVNS stimulation

Electrical stimulation to the cymba concha or tragus (depending on the ear dimension) of the outer ear on the right side after successful trials.

Intervention Type PROCEDURE

Unilateral Right Sham stimulation

Electrical stimulation to the earlobe of the outer ear on the right side after successful trials.

Intervention Type PROCEDURE

Eligibility Criteria

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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
Minimum Eligible Age

18 Years

Maximum Eligible Age

89 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

Yes

Sponsors

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Emory University

OTHER

Sponsor Role collaborator

Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)

NIH

Sponsor Role collaborator

Georgia Institute of Technology

OTHER

Sponsor Role lead

Responsible Party

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Responsibility Role SPONSOR

Principal Investigators

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Minoru Shinohara, Ph.D.

Role: PRINCIPAL_INVESTIGATOR

Georgia Institute of Technology

Locations

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Human Neuromuscular Physiology Lab

Atlanta, Georgia, United States

Site Status

Countries

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United States

Provided Documents

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Document Type: Informed Consent Form

View Document

Other Identifiers

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5P2CHD086844-09

Identifier Type: NIH

Identifier Source: secondary_id

View Link

H24109

Identifier Type: -

Identifier Source: org_study_id

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