40 Hz Transcranial Alternating Current Stimulation for Inducing Gamma Oscillations

Induction and Stabilization of Gamma Oscillations With 40 Hz Transcranial Alternating Current Stimulation in Healthy Elderly

This study aims to compare the efficacy of different 40 Hz tACS protocols in entraining gamma oscillations, which are linked to various cognitive functions and play a significant role in cognitive impairments like Alzheimer's disease. Specifically, it examines the effects of 40 Hz tACS applied to frontal brain regions versus fronto-temporal regions on gamma oscillations and working memory in healthy elderly individuals.

Study Overview

• Status: Completed
• Conditions: Alzheimer Disease; Cognitive Decline
• Intervention / Treatment: Device: Transcranial alternating current stimulation; Device: Sham Transcranial alternating current stimulation

• Study Type: Interventional
• Enrollment (Actual): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Iran
  • Tehran, Iran
    • Institute for Research in Fundamental Sciences

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• healthy elderly between 50-80 years of age
• normal or corrected to normal eye vision
• right-handed
• non-smokers
• at least 70 % accuracy in working memory training task

Exclusion Criteria:

• history of neurological or psychiatric disorders including seizures or epilepsy,
• Taking CNS, blood pressure and other medications
• having metal implants in the head and neck
• significant cognitive decline meassured by The Montreal Cognitive Assessment (MoCA)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: 40 Hz prefrontal Transcranial alternating current stimulation; During prefrontal tACS, an alternating electrical current with a 1 milliamp peak-to-peak amplitude will be delivered, featuring a 15-second ramp-up at the start and a 15-second ramp-down at the end. The stimulation duration is 20 minutes and four channels are used for delivering sinusoidal alternating currents to the head. The alternating current was delivered to the prefrontal cortex bilaterally with the electrodes at F3 and F4 and the return electrodes were placed at the ipsilateral mastoids at TP9 and TP10 (international 10-20 EEG electrode placement system).	Device: Transcranial alternating current stimulation; Transcranial alternating current will be delivered utilizing a Starstim 8-channel constant current, battery-powered electric stimulator (Neuroelectrics, Barcelona, Spain). Circular carbon rubber electrodes (2cm radius, 12,57 cm2) are used throughout the stimulation.
Active Comparator: 40 Hz frontal-temporal Transcranial alternating current stimulation; During frontal-temporal tACS, an alternating electrical current with a personalized peak-to-peak stimulation intensity will be delivered, featuring a 15-second ramp-up at the start and a 15-second ramp-down at the end. The stimulation duration is 20 minutes and four channels are used for delivering sinusoidal alternating currents to the head. The alternating current was delivered to the prefrontal and temporal cortices with the active electrodes at AF3-T7 and the return electrodes over AF4-T8 (according international 10-20 EEG electrode placement system).	Device: Transcranial alternating current stimulation; Transcranial alternating current will be delivered utilizing a Starstim 8-channel constant current, battery-powered electric stimulator (Neuroelectrics, Barcelona, Spain). Circular carbon rubber electrodes (2cm radius, 12,57 cm2) are used throughout the stimulation.
Sham Comparator: sham Transcranial alternating current stimulation; During sham tACS, an alternating artificial electrical current will be delivered, only ramping the current for 15 seconds up and 15 seconds down at the beginning and end of the stimulation respectively.	Device: Sham Transcranial alternating current stimulation; Sham tACS will be applied by only ramping the current for 15 seconds up and 15 seconds down at the beginning and end of the stimulation respectively.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Working Memory behavioral performance	Participants view a continuous sequence of alphabet letters, presented as stimuli in Arial font, size 120pt, on a tube screen positioned at 60cm eye distance. The stimuli are shown with a time interval of two seconds between them. The task consisted of six blocks with 70 stimuli, including 12 possible hit trials. Participants were instructed to press the left key on a response box if the presented stimulus matched either the one presented one trial prior (1-Back) or three trials prior (3-Back). In all other cases, participants press the right key. The left button is pressed with the index finger, while the right button is pressed with the middle finger of the right hand, with buttons aligned horizontally. The response condition varied by block, with three blocks for 3-Back and three for 1-Back, and the order was counterbalanced across participants and sessions.	During procedure (20 minutes)
electroencephalogram (EEG) oscillatory power	Change in the EEG power in the gamma band	up to 2 hours after the intervention
electroencephalogram (EEG) functional connectivity	Change in EEG functional connectivity, specifically global efficiency, coherence, and phase-locking value at gamma frequency	up to 2 hours after the intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
electroencephalogram (EEG) oscillatory power	Change in the EEG power in alpha, delta, theta and beta bands	up to 2 hours after the intervention

Collaborators and Investigators

• Sponsor: The National Brain Mapping Laboratory (NBML)
• Collaborators: Leibniz Research Centre for Working Environment and Human Factors; Technical University of Dortmund; Institute for Research in Fundamental Sciences (IPM)

Study record dates

Study Major Dates

• Study Start (Actual): June 1, 2024
• Primary Completion (Actual): February 1, 2025
• Study Completion (Actual): June 1, 2025

Study Registration Dates

• First Submitted: December 14, 2024
• First Submitted That Met QC Criteria: December 14, 2024
• First Posted (Actual): December 18, 2024

Study Record Updates

• Last Update Posted (Actual): March 18, 2026
• Last Update Submitted That Met QC Criteria: March 15, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Mental Disorders; Neurocognitive Disorders; Cognition Disorders; Dementia; Tauopathies; Neurodegenerative Diseases; Cognitive Dysfunction; Alzheimer Disease; Therapeutics; Behavioral Disciplines and Activities; Electric Stimulation Therapy; Convulsive Therapy; Psychiatric Somatic Therapies; Electroshock; Psychological Techniques; Transcranial Direct Current Stimulation
• Other Study ID Numbers: IfADo_196_P3

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No