Gamma Transcranial Alternating Current Stimulation in Healthy Adults
For patients and families
In plain language
An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.
- What is being studied
- The protocol lists: Application of Tacs.
- Who it may be relevant to
- Registry conditions: Healhty. Basic parameters: 18 years — 40 years · All.
- What needs checking
- Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
- Where it takes place
- Turkey (Türkiye)
- Next step
- Save the trial, show it to the treating physician, and confirm current recruitment with the study center. Costs, documents and travel →
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Official title
Modulation of Cross-Frequency Theta-Gamma Coupling Via Gamma Transcranial Alternating Current Stimulation in Healthy Adults
Overview
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.
Interventions
- Device Application of Tacs
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 wi
Primary outcome measures
- Öktem Verbal Memory Test [Time frame: Before and immediately after applying Tacs]
- Resting State EEG and TASK EEG [Time frame: Before and immediately after applying Tacs]
- Forward and Backward Digit Span [Time frame: Before and immediately after applying Tacs]
- Verbal fluency tests [Time frame: Before and immediately after applying Tacs]
Eligibility criteria
Inclusion criteria
- 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
Exclusion criteria
Having a neurological or psychiatric disorder
Use of medications with sedative or stimulant effects
Presence of metal brain implants or a pacemaker
Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.
Healthy volunteers: Yes
Study design
- Allocation
- Randomized
- Model
- Factorial
- Masking
- Single blind
- Primary purpose
- Basic science
Study locations
Turkey (Türkiye) · 1 center
- Medipol University — Istanbul
Identifiers
NCT: NCT07095218 · E-10840098-202.3.02-2205