Sham transcranial alternating current stimulation will use the same electrode montage, device appearance, and setup procedures as active tACS. Electrodes will be placed at F4, F2, AF4, and F6 over the right frontal region, and at P4, CP4, P6, and PO4 over the right parietal region. F4 and P4 will be configured as return electrodes as in the active stimulation condition. The sham procedure will include brief ramp-up and ramp-down periods of approximately 60 seconds to mimic the sensory experience of active stimulation, with no sustained current delivered.

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.