HealhtyNCT07095218
Gamma Transcranial Alternating Current Stimulation in Healthy Adults
A study testing Application of Tacs in people with Healhty, run by Medipol University at 1 site in Turkey (Türkiye).
Trial summary
Transcranial Alternating Current Stimulation (tACS), particularly at gamma frequencies, may enhance fast brain oscillations (especially gamma and possibly beta), while reducing slower rhythms such as theta. Read more about this study
- Who is it for?
- Ages 18 to 40 yearsHealthy volunteers can take part
- Conditions the study is for
- Healhty
- What is being tested?
- Application of Tacs
- Type of treatment
- Medical device
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 60 participants
- Where
- 1 siteTurkey (Türkiye)
- Study dates
- 1 Jun 2025to 30 May 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 40 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Being between 18 and 40 years of age
- Scoring above 25 on the Montreal Cognitive Assessment (MoCA)
- Being right-handed
- Having no history of neurological or psychiatric diagnosis
Who cannot join
- Having a neurological or psychiatric disorder
- Use of medications with sedative or stimulant effects
- Presence of metal brain implants or a pacemaker
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
About this study
Official title: Modulation of Cross-Frequency Theta-Gamma Coupling Via Gamma Transcranial Alternating Current Stimulation in Healthy Adults
Transcranial Alternating Current Stimulation (tACS), particularly at gamma frequencies, may enhance fast brain oscillations (especially gamma and possibly beta), while reducing slower rhythms such as theta. These effects are not confined to the stimulation site (e.g., the precuneus) but can extend to structurally and functionally connected regions, including the default mode network (DMN). Notably, 40 Hz gamma tACS applied to the left dorsolateral prefrontal cortex (DLPFC) has been associated with improvements in working memory and motor learning during reaction time tasks. While beta-frequency stimulation often shows no significant effect, gamma-frequency tACS has been shown to reduce response times.
Gamma oscillations are commonly disrupted in neuropsychiatric disorders. These rhythms depend on a balance between excitation and inhibition, possibly linked to interneuron dysfunction. Abnormal gamma activity has been proposed as a biomarker for cognitive impairment. In this context, non-invasive rhythmic stimulation aiming to restore gamma activity is a promising cognitive enhancement strategy, though unlike pharmacological approaches, gamma-tACS has not yet been widely adopted in clinical practice.
Read more
A meta-analysis of 56 studies emphasized that tACS outcomes vary with stimulation frequency, brain region, and timing protocols. Research suggests that the susceptibility of gamma oscillations to external modulation may provide insights into cognitive reserve, domain-specific processes, and Alzheimer's disease progression. Oscillatory changes may help predict conversion from MCI to Alzheimer's disease. However, evidence on the neural mechanisms of tACS remains limited and heterogeneous, and outcomes appear to depend on task type, frequency, and intensity.
In this study, we will deliver a single 20-minute tACS session over the bilateral DLPFC using gamma frequencies (40 Hz, 80 Hz, and individualized gamma), and a theta-gamma coupling range (6-80 Hz). A sham group will also be included. The anodal electrode will be placed over F3, and the cathodal electrode over F4 (10-20 system). Cognitive performance will be assessed pre- and post-stimulation using neuropsychological tests, and EEG will measure theta-gamma phase-amplitude coupling and changes in oscillatory activity.
- Conditions
- Healhty
- Being tested
- Application of Tacs
- Keywords
- gamma, tACS, theta-gamma coupling
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Application of TacsDevice
In this study, a single 20-minute session of tACS will be administered over the bilateral dorsolateral prefrontal cortex (DLPFC) at various gamma frequencies (40 Hz, 80 Hz, individual gamma frequency) and in a theta-gamma coupling range (6-80 Hz). A sham stimulation group will also be included. The anodal surface electrode will be placed over the left DLPFC (F3 according to the 10-20 system), and the cathodal electrode over the right DLPFC (F4). Pre- and post-stimulation cognitive performance will be assessed using neuropsychological tests, while EEG will be used to evaluate theta-gamma phase-amplitude coupling and oscillatory changes.
| Study group | Role | What they receive |
|---|---|---|
| 80 Hz Group | Experimental | transcranial alternating current stimulation (tACS) at 80 Hz gamma frequency will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. Receives: Device: Application of Tacs |
| 40 Hz Group | Experimental | transcranial alternating current stimulation (tACS) at 40 Hz gamma frequency will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. Receives: Device: Application of Tacs |
| Individual gamma Group | Experimental | transcranial alternating current stimulation (tACS) at ındividual (Hz) gamma frequency will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. Receives: Device: Application of Tacs |
| 6-80 Hz Group | Experimental | transcranial alternating current stimulation (tACS) at 6-80 Hz will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. Receives: Device: Application of Tacs |
| Sham Group | Placebo comparator | transcranial alternating current stimulation (tACS) at sham will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. Receives: Device: Application of Tacs |
What is being measured
The primary outcome is the main question the study is designed to answer.
Öktem Verbal Memory Test
Öktem Verbal Memory Test is a test of verbal memory processes, developed and validated by Öktem in 1992. It is designed to measure various variables related to memory.
Measured: Before and immediately after applying Tacs
Resting State EEG and TASK EEG
The EEG recordings of the participants will be conducted using a BrainAmp 64-channel DC system. A 64-channel EasyCap will be used. AFz will serve as the ground electrode, and FCz will be used as the reference electrode. Impedance values will be maintained below 10 kOhm. EEG data will be recorded using the BrainVision Recorder software (Brain Products, Munich, Germany) with a band-pass filter set between 0.01 and 250 Hz.A 4-minute eyes-open and a 4-minute eyes-closed resting-state EEG recording will be conducted. EEG will also be recorded during the 2-back task and the memory task.
2-back Task: A visual n-back task will be administered to assess working memory. The task load will consist of 8-minute sessions.
Memory Task:
The memory task, which involves both encoding and retrieval of episodic information, will be examined using a visual memory paradigm presented to the participants.
Measured: Before and immediately after applying Tacs
Forward and Backward Digit Span
This test, which is a subtest of the Wechsler Memory Scale, was developed to assess overall attention. It consists of two stages. The first stage evaluates the forward digit span, composed of random sequences ranging from 2 to 8 digits. In the second stage, the backward digit span is assessed using random sequences of 2 to 7 digits. In the first stage, numbers are read aloud with one-second intervals, and participants are expected to repeat the sequences exactly as presented. In the second stage, numbers are again read with one-second intervals, but participants are required to repeat the digits in reverse order. The test is terminated if the participant makes consecutive errors. The forward digit span assesses sustained attention, while the backward span also evaluates working memory performance.
Measured: Before and immediately after applying Tacs
Verbal fluency tests
Verbal fluency tests measure the ability to generate words within a specific category over a limited time period. Verbal fluency performance has been associated not only with general language skills and semantic memory functions but also with executive functions such as attention, working memory, and processing speed. In this study, semantic and phonemic fluency tasks will be used.
Measured: Before and immediately after applying Tacs
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted31 Jul 2025
- Study start1 Jun 2025
- Primary completion30 Dec 2026 (estimated)
- Study completion30 May 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HealhtyStudies of the same condition, open and under way.
- More trials run by Medipol UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Factorial
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 60 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Medipol University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, FATMA AYDIN, Medipol University
- Investigators
- Lütfü Hanoğlu, Study director, Medipol University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07095218
- Sponsor's protocol ID
- E-10840098-202.3.02-2205
- Status last verified
- Jul 2025
- First submitted
- 7 Jul 2025
- Last updated
- 31 Jul 2025
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 31 Jul 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Modulation of Cross-Frequency Theta-Gamma Coupling Via Gamma Transcranial Alternating Current Stimulation in Healthy Adults
- ClinicalTrials.gov ID
- NCT07095218
- Acronym / sponsor ID
- E-10840098-202.3.02-2205
- Conditions
- Healhty
- Keywords
- gamma, tACS, theta-gamma coupling
- Study type
- Interventional
- Recruitment status
- Enrolling by invitation
- Enrolment
- 60 participants (estimated)
- Lead sponsor
- Medipol UniversityUniversity, hospital or other
- Study start
- 1 Jun 2025 (actual)
- Primary completion
- 30 Dec 2026 (estimated)
- Study completion
- 30 May 2027 (estimated)
- First posted
- 31 Jul 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Transcranial Alternating Current Stimulation (tACS), particularly at gamma frequencies, may enhance fast brain oscillations (especially gamma and possibly beta), while reducing slower rhythms such as theta. These effects are not confined to the stimulation site (e.g., the precuneus) but can extend to structurally and functionally connected regions, including the default mode network (DMN). Notably, 40 Hz gamma tACS applied to the left dorsolateral prefrontal cortex (DLPFC) has been associated with improvements in working memory and motor learning during reaction time tasks. While beta-frequency stimulation often shows no significant effect, gamma-frequency tACS has been shown to reduce response times.
Gamma oscillations are commonly disrupted in neuropsychiatric disorders. These rhythms depend on a balance between excitation and inhibition, possibly linked to interneuron dysfunction. Abnormal gamma activity has been proposed as a biomarker for cognitive impairment. In this context, non-invasive rhythmic stimulation aiming to restore gamma activity is a promising cognitive enhancement strategy, though unlike pharmacological approaches, gamma-tACS has not yet been widely adopted in clinical practice.
A meta-analysis of 56 studies emphasized that tACS outcomes vary with stimulation frequency, brain region, and timing protocols. Research suggests that the susceptibility of gamma oscillations to external modulation may provide insights into cognitive reserve, domain-specific processes, and Alzheimer's disease progression. Oscillatory changes may help predict conversion from MCI to Alzheimer's disease. However, evidence on the neural mechanisms of tACS remains limited and heterogeneous, and outcomes appear to depend on task type, frequency, and intensity.
In this study, we will deliver a single 20-minute tACS session over the bilateral DLPFC using gamma frequencies (40 Hz, 80 Hz, and individualized gamma), and a theta-gamma coupling range (6-80 Hz). A sham group will also be included. The anodal electrode will be placed over F3, and the cathodal electrode over F4 (10-20 system). Cognitive performance will be assessed pre- and post-stimulation using neuropsychological tests, and EEG will measure theta-gamma phase-amplitude coupling and changes in oscillatory activity.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Factorial
- Masking
- Single blind (participant)
- Number of arms
- 5
| Arm | Type | Receives |
|---|---|---|
| 80 Hz Group | Experimental | Device: Application of Tacstranscranial alternating current stimulation (tACS) at 80 Hz gamma frequency will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. |
| 40 Hz Group | Experimental | Device: Application of Tacstranscranial alternating current stimulation (tACS) at 40 Hz gamma frequency will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. |
| Individual gamma Group | Experimental | Device: Application of Tacstranscranial alternating current stimulation (tACS) at ındividual (Hz) gamma frequency will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. |
| 6-80 Hz Group | Experimental | Device: Application of Tacstranscranial alternating current stimulation (tACS) at 6-80 Hz will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. |
| Sham Group | Placebo comparator | Device: Application of Tacstranscranial alternating current stimulation (tACS) at sham will be applied to the bilateral dorsolateral prefrontal cortex (DLPFC) in a single 20-minute session. |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Being between 18 and 40 years of age
- Scoring above 25 on the Montreal Cognitive Assessment (MoCA)
- Being right-handed
- Having no history of neurological or psychiatric diagnosis
Key exclusion criteria (3 listed)
- Having a neurological or psychiatric disorder
- Use of medications with sedative or stimulant effects
- Presence of metal brain implants or a pacemaker
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Application of TacsIn this study, a single 20-minute session of tACS will be administered over the bilateral dorsolateral prefrontal cortex (DLPFC) at various gamma frequencies (40 Hz, 80 Hz, individual gamma frequency) and in a theta-gamma coupling range (6-80 Hz). A sham stimulation group will also be included. The anodal surface electrode will be placed over the left DLPFC (F3 according to the 10-20 system), and the cathodal electrode over the right DLPFC (F4). Pre- and post-stimulation cognitive performance will be assessed using neuropsychological tests, while EEG will be used to evaluate theta-gamma phase-amplitude coupling and oscillatory changes. | Device | 40 Hz Group, 6-80 Hz Group, 80 Hz Group, Individual gamma Group, Sham Group |
Primary outcome
Öktem Verbal Memory Test
Time frame: Before and immediately after applying Tacs
Öktem Verbal Memory Test is a test of verbal memory processes, developed and validated by Öktem in 1992. It is designed to measure various variables related to memory.
Resting State EEG and TASK EEG
Time frame: Before and immediately after applying Tacs
The EEG recordings of the participants will be conducted using a BrainAmp 64-channel DC system. A 64-channel EasyCap will be used. AFz will serve as the ground electrode, and FCz will be used as the reference electrode. Impedance values will be maintained below 10 kOhm. EEG data will be recorded using the BrainVision Recorder software (Brain Products, Munich, Germany) with a band-pass filter set between 0.01 and 250 Hz.A 4-minute eyes-open and a 4-minute eyes-closed resting-state EEG recording will be conducted. EEG will also be recorded during the 2-back task and the memory task. 2-back Task: A visual n-back task will be administered to assess working memory. The task load will consist of 8-minute sessions. Memory Task: The memory task, which involves both encoding and retrieval of episodic information, will be examined using a visual memory paradigm presented to the participants.
Forward and Backward Digit Span
Time frame: Before and immediately after applying Tacs
This test, which is a subtest of the Wechsler Memory Scale, was developed to assess overall attention. It consists of two stages. The first stage evaluates the forward digit span, composed of random sequences ranging from 2 to 8 digits. In the second stage, the backward digit span is assessed using random sequences of 2 to 7 digits. In the first stage, numbers are read aloud with one-second intervals, and participants are expected to repeat the sequences exactly as presented. In the second stage, numbers are again read with one-second intervals, but participants are required to repeat the digits in reverse order. The test is terminated if the participant makes consecutive errors. The forward digit span assesses sustained attention, while the backward span also evaluates working memory performance.
Verbal fluency tests
Time frame: Before and immediately after applying Tacs
Verbal fluency tests measure the ability to generate words within a specific category over a limited time period. Verbal fluency performance has been associated not only with general language skills and semantic memory functions but also with executive functions such as attention, working memory, and processing speed. In this study, semantic and phonemic fluency tasks will be used.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 31 Jul 2025.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Lütfü Hanoğlu study director
Medipol University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Application of Tacs in people with Healhty, run by Medipol University at 1 site in Turkey (Türkiye).
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: enrolling by invitation, as of the sponsor's last update on 31 Jul 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Öktem Verbal Memory Test (time frame: Before and immediately after applying Tacs). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 31 Jul 2025.