Modulating Oscillations and Working Memory in Patients With Subdural Electrodes

March 16, 2026 updated by: University of North Carolina, Chapel Hill

Purpose: To investigate whether rhythmic direct electrical stimulation (DES) causes entrainment of endogenous neural oscillatory activity and whether such activity improve cognition.

Participants: Drug-resistant epilepsy patients undergoing epilepsy surgery cortical mapping with continuous electrocorticography (ECoG) with intracranial electrodes.

Procedures (methods): Rhythmic electrical stimulation will be delivered via intracranial electrodes during routine extra-operative cortical mapping. Long-term ECoG, Pre-stimulation ECoG, peri-stimulation ECoG, and post-stimulation ECoG data will be analyzed to assess for entrainment of neural oscillations.

Study Overview

Status

Status

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Withdrawn

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

The aim of this study is to characterize the entrainment of endogenous neural oscillatory activity using direct electrical stimulation (DES) of the brain and understand the effects on cognition.

In this study, the investigators will apply rhythmic DES to patients who are undergoing routine DES for cortical mapping as a part of their epilepsy surgery evaluation with the aim of entraining cortical neural oscillations at specific frequencies relevant to cognitive processing and neuropsychiatric disease. The investigators hypothesize that rhythmic DES within a naturally occurring oscillatory frequency will cause entrainment at that frequency (e.g. 10Hz rhythmic DES will entrain a 10 Hz alpha oscillation). Also, the investigators posit that rhythmic DES at the theta (5Hz), alpha(10Hz), and gamma (50Hz) frequencies will cause enhancement of neural oscillations in the gamma band.

The study follows a within-participant crossover design. Participants will perform one of the tasks described below and each task consists of multiple trials of varying difficulty. Stimulation will be applied concurrently through electrodes implanted for clinical determination of seizure focus. Equal number of stimulation and sham trials will be pseudo-randomly interleaved to get a balanced design (balanced across trial difficulty and trial type).

The investigators will apply electrical stimulation in the form of pulse trains. The applied electrical stimulation intensity, duration and frequency follow the parameters used for clinical assessments of language and seizure focus and fall below the clinically approved limits.

The investigators will measure participants performance on a simple working memory task during the above-described cortical electrical stimulation protocol. Alternately, participants can perform a face recognition task.

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

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

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

18 years to 80 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  1. History of medically intractable epilepsy
  2. Capable of giving informed consent
  3. Aged 18 - 80 years, either sex

Exclusion Criteria:

  1. Past or current history of other neurological illnesses including ischemic stroke, intracerebral hemorrhage, brain neoplasm.
  2. Major systemic illness
  3. Severe cognitive impairment defined as mini-mental state examination of less than 20
  4. Severe psychiatric illness
  5. Excessive use of alcohol or other substances

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: Non-Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Single

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.
Sham Comparator: Sham
Device: Direct Cortical Stimulation Sham. Trials in which stimulation is not applied. These trials are initiated using a generic trigger generator.
Device: Direct Cortical Stimulation Sham
Sham trials where no electric pulse is delivered
Active Comparator: Stimulation
Device: Direct Cortical Stimulation. 150 stimulations with stimulations lasting 5 seconds at different target electrodes at two target frequencies (e.g. 5 Hz and 10 Hz) 2 milliampere in amplitude (Pulse shape - Biphasic square pulse 200 microsecond in duration per phase). Stimulation will be applied concurrently with the task and stimulation trials will be randomly interleaved with sham trials.
Device: Direct Cortical Stimulation
A train of periodic electrical pulses is delivered between two local electrodes implanted in the brain

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
Working Memory Task Performance - Accuracy
Time Frame: 1 Hour
In this task, a sequence of items (alphabets or numerals) is presented followed by a delay. Following this, a single item which may or may not have been in the sequence is presented and the subject will be asked to indicate whether the item was in the previously presented sequence. A total of 150 trials will be performed with randomly interleaved sham trials where no stimulation is applied. Accuracy will be quantified in percentage correct.
1 Hour
Working Memory Task Performance - Reaction Time
Time Frame: 1 Hour
In this task, a sequence of items (alphabets or numerals) is presented followed by a delay. Following this, a single item which may or may not have been in the sequence is presented and the subject will be asked to indicate whether the item was in the previously presented sequence. A total of 150 trials will be performed with randomly interleaved sham trials where no stimulation is applied. Reaction times will be quantified in milliseconds.
1 Hour

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Intracranial EEG
Time Frame: Intracranial EEG will be collected simultaneously when the participants perform the task. 1 Hour
Spectral analysis and functional connectivity analysis of electrophysiology data will be performed using methods like multi-taper fft, wavelets, phase locking, Granger causality etc. The measures will be compared between sham and stimulation trials to identify if stimulation enhances neuronal entrainment. The correlation between the measures described above and the task performance will also be estimated.
Intracranial EEG will be collected simultaneously when the participants perform the task. 1 Hour

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Facial Recognition Task Performance - Accuracy
Time Frame: 1 Hour
Participants who consent will be administered this task. On a given trial, participants will be presented with images of two faces side-by-side. The faces will either match in terms of emotion category (e.g., 2 anger faces) or not (e.g., an anger face and a fear face). Faces presented together will always be of the same gender but different identities. Participants will be asked to determine whether the two faces presented depict the same emotion category. Participants will have 5 seconds to make the decision and indicate by pressing a key in the keyboard. Accuracy will be quantified in percent correct.
1 Hour
Facial Recognition Task Performance - Reaction Time
Time Frame: 1 Hour
Participants who consent will be administered this task. On a given trial, participants will be presented with images of two faces side-by-side. The faces will either match in terms of emotion category (e.g., 2 anger faces) or not (e.g., an anger face and a fear face). Faces presented together will always be of the same gender but different identities. Participants will be asked to determine whether the two faces presented depict the same emotion category. Participants will have 5 seconds to make the decision and indicate by pressing a key in the keyboard. Reaction times will be quantified in milliseconds.
1 Hour

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.
University of North Carolina, Chapel Hill

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.
National Institute of Neurological Disorders and Stroke (NINDS)

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: Hae Won Shin, MD, University of North Carolina, Chapel Hill
  • Principal Investigator: Flavio Frohlich, PhD, University of North Carolina, Chapel Hill

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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.
January 1, 2014

Primary Completion (Estimated)

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.
March 15, 2017

Study Completion (Estimated)

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.
March 15, 2017

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).
February 22, 2017

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.
April 6, 2017

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.
April 12, 2017

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.
March 19, 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.
March 16, 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.
January 1, 2025

More Information

Terms related to this study

Keywords

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.
  • 13-2710
  • 1R21NS094988 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified electrophysiology data and task information (e.g. timing of each trial, timing of responses) will be shared at the end of the study in a central repository (e.g. zenodo)

Study Data/Documents

  1. Summary Data Set
    Information comments: Dataset supporting Alagapan et al. 2016 PLoS Biology

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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