Attention-Deficit/Hyperactivity Disorder (ADHD) is a common neurodevelopmental disorder characterized by symptoms of inattention, impulsivity, and hyperactivity. These symptoms are often associated with impairments in executive functions and working memory, which are essential for goal-directed behavior and cognitive control. Deficits in these domains can significantly hinder individuals' academic, social, and daily functioning. Gamma oscillations (30-80 Hz) play a crucial role in cognitive integration, attention, and memory processes, and are thought to emerge from the balance between excitatory and inhibitory neuronal activity. Transcranial Alternating Current Stimulation (tACS) is a non-invasive brain stimulation technique that modulates neuronal activity through rhythmic electrical currents. Recent studies suggest that gamma-frequency tACS applied to the prefrontal cortex can enhance cognitive performance and attentional processes. In individuals with ADHD, disrupted gamma connectivity and reduced regional gamma power have been associated with attentional deficits. Therefore, gamma tACS may modulate both regional activity and long-range functional connectivity, offering a promising neuromodulation strategy to alleviate ADHD symptoms. In this context, the present study aims to investigate the effects of bilateral gamma-frequency tACS applied to the prefrontal cortex on attention and executive function performance in individuals with ADHD. Changes in gamma oscillatory activity will be measured using EEG to assess the neurophysiological impacts of stimulation. The study seeks to evaluate whether gamma tACS can serve as a targeted, evidence-based intervention to address the neurofunctional deficits observed in ADHD, potentially offering a novel therapeutic approach.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
60
In this study, a single 20-minute session of tACS will be administered over the bilateral dorsolateral prefrontal cortex (DLPFC) at various gamma frequencies (80 Hz).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).
In this study, a single 20-minute session of tACS will be administered over the bilateral dorsolateral prefrontal cortex (DLPFC) at gamma frequencies (40 Hz). 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).
In this study, a single 20-minute session of tACS will be administered over the bilateral dorsolateral prefrontal cortex (DLPFC) at theta- gamma coupling frequencies ( 6-80 Hz). 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).
In this study, a single 20-minute session of tACS will be administered over the bilateral dorsolateral prefrontal cortex (DLPFC) at individual gamma frequencies . 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).
In this study, a single 20-min tACS session will be applied over the bilateral dorsolateral prefrontal cortex (DLPFC) in a sham application. The anodal surface electrode will be placed over the left DLPFC (F3 of the 10-20 system) and the cathodal electrode will be placed over the right DLPFC (F4).
Medipol University Istanbul
Istanbul, Turkey (Türkiye)
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.
Time frame: Pre-tACS Baseline (prior to stimulation) / Post-tACS (within 30 minutes after stimulation)
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.
Time frame: Pre-tACS Baseline (prior to stimulation) / Post-tACS (within 30 minutes after stimulation)
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.
Time frame: Pre-tACS Baseline (prior to stimulation) / Post-tACS (within 30 minutes after stimulation)
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.
Time frame: Pre-tACS Baseline (prior to stimulation) / Post-tACS (within 30 minutes after stimulation)
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