Anodal tDCS Over Left PPC Enhances Visuospatial Attention and Alpha Power Among Young Adults

Background: Visuospatial attention enables individuals to detect and process relevant stimuli efficiently. The posterior parietal cortex (PPC), a core hub of the dorsal attention network, exerts top-down control over visual scanning and is closely linked to alpha-band oscillations (8-13 Hz), which index attentional allocation and inhibition of distractors. Transcranial direct current stimulation (tDCS) offers a noninvasive method to alter cortical excitability transiently, but evidence for its effects on PPC-mediated attention and alpha power remains mixed. Objective: This randomized, single-blind trial examined whether anodal tDCS over the left PPC modulates visuospatial attention and resting-state alpha power in young adults, and whether EEG changes predict behavioral performance. Method: Thirty-two healthy participants (18-40 years) were randomized to anodal (2 mA, 20 min; n=15) or sham (n=17) stimulation. Cancellation Test performance and resting-state EEG were assessed pre- and post-stimulation. EEG analyses focused on artifact-free alpha power; regression models probed associations between neural and behavioral changes.

Inclusion Criteria: * Age between 18 and 40 years * Score of 21 or higher on the Montreal Cognitive Assessment Scale (MoCA) Exclusion Criteria: * History of neurological or psychiatric illness * Uncorrected visual impairments * MoCA score of 21 or lower * Use of medications affecting cortical excitability * History of seizures or epilepsy * Presence of intracranial metal objects, implanted stimulating devices, or pacemakers