Fronto-Parietal Transcranial Alternating Current Stimulation for ADHD in Children and Adolescents

Attention performance will be assessed using the Test of Attentional Performance for Children, including seven child-adapted attention subtests covering alertness, distractibility, divided attention, cognitive flexibility, response inhibition, sustained attention, and visual scanning. Outcome indices include reaction time, reaction time variability, accuracy, omission errors, commission errors, and other task-specific performance measures. In general, shorter reaction time, lower reaction time variability, higher accuracy, and fewer errors indicate better attention performance.

Task-related electroencephalography will be recorded during a visual search task in which participants identify the direction of a visual target and respond using a joystick. EEG outcomes will include event-related potential measures, such as N2pc amplitude and latency, time-frequency measures across predefined frequency bands, and alpha-band channel tuning function indices reflecting spatially selective neural responses. These measures do not have a fixed clinical score range.

ADHD symptoms will be assessed using the parent-rated Swanson, Nolan, and Pelham-IV Rating Scale 26-item version (SNAP-IV). The scale includes items assessing inattention, hyperactivity/impulsivity, and oppositional symptoms. Each item is rated on a 4-point scale: 0 = not at all, 1 = just a little, 2 = quite a bit, and 3 = very much. Total score and subscale scores are calculated by summing or averaging the relevant items. Higher scores indicate more severe ADHD-related and oppositional symptoms.

Behavioral abnormalities will be assessed using the Aberrant Behavior Checklist-Second Edition (ABC-II). The ABC-II evaluates the frequency and severity of behavioral problems. Each item is rated on a 4-point scale: 0 = not a problem, 1 = the behavior is a problem but slight in degree, 2 = the problem is moderately serious, and 3 = the problem is severe. The total score is calculated by summing all item scores. Higher scores indicate more severe and widespread behavioral problems.

Depressive symptoms will be assessed using the Patient Health Questionnaire-9 (PHQ-9). The PHQ-9 includes 9 items assessing depressive symptoms during the past two weeks. Each item is rated on a 4-point scale: 0 = not at all, 1 = several days, 2 = more than half the days, and 3 = nearly every day. The total score ranges from 0 to 27, with higher scores indicating more severe depressive symptoms.

Anxiety symptoms will be assessed using the Generalized Anxiety Disorder-7 scale (GAD-7). The GAD-7 includes 7 items assessing the frequency of anxiety-related symptoms during the past two weeks. Each item is rated on a 4-point scale: 0 = not at all, 1 = several days, 2 = more than half the days, and 3 = nearly every day. The total score ranges from 0 to 21, with higher scores indicating more severe anxiety symptoms.

Sleep problems will be assessed using the Sleep Disturbance Scale for Children (SDSC). The SDSC is a parent-rated questionnaire assessing sleep-related problems in children and adolescents. Items are rated according to the frequency or severity of sleep disturbances on a 5-point scale. The total score is calculated by summing item scores. Higher scores indicate more severe sleep disturbances.

Sensory processing symptoms will be assessed using the Short Sensory Profile (SSP). The SSP is a parent-rated questionnaire assessing sensory processing patterns and sensory-related behavioral responses in children. Each item is rated on a 5-point scale according to how frequently the child shows a specific sensory response. The total score is calculated by summing item scores. Lower scores generally indicate greater sensory processing difficulties, whereas higher scores indicate fewer sensory processing difficulties.

Selective attention performance will be assessed using a joystick-based visual search task. Participants will be asked to identify the direction or location of a visual target and respond using a joystick. Behavioral outcome indices will include predefined task performance measures, such as reaction time, movement time, response accuracy, response variability, omission errors, commission errors, and other task-specific joystick response measures. In general, shorter reaction time and movement time, lower response variability, higher accuracy, and fewer errors indicate better selective attention performance.

Resting-state electroencephalography will be recorded to assess spontaneous neural activity. EEG spectral outcomes will include power measures across predefined frequency bands and parameterized spectral measures derived from the power spectrum, such as aperiodic offset, aperiodic exponent, and periodic oscillatory components. These measures do not have a fixed clinical score range.