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.

Study Overview

• Status: Completed
• Conditions: tDCS; EEG; Visual Attention; Posterior Parietal Cortex
• Intervention / Treatment: Device: Anodal tDCS; Device: Sham tDCS

• Study Type: Interventional
• Enrollment (Actual): 32
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • İ̇stanbul
    • Beykoz, İ̇stanbul, Turkey (Türkiye), 34820
      • Istanbul Medipol University

Participation Criteria

Eligibility Criteria

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

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Anodal tDCS Group	Device: Anodal tDCS; Anodal tDCS Protocol: In the Anodal tDCS participant group, a direct current of 2 mA was applied for 20 minutes in accordance with the safety guidelines. To provide cortical stimulation, the superficial anodal electrode of the device was placed on the P3 region (left PPC), which is located in the left superior parietal lobe, corresponds to Brodmann area (BA) 40, and is associated with the dorsal visual pathway according to the international 10-20 EEG system. The reference electrode was placed on the contralateral (opposite) shoulder.
Sham Comparator: Sham tDCS Group	Device: Sham tDCS; Sham tDCS Protocol: The anode superficial electrode of the device was placed on the P3 region (left PPC), located in the left superior parietal lobe, corresponding to Brodmann area (BA) 40, and associated with the dorsal visual pathway according to the international 10-20 EEG system. The reference electrode was placed on the contralateral (opposite) shoulder. In the Sham tDCS group, a single 20-minute sham session was administered over the left posterior parietal cortex (P3) without delivering current, in accordance with the safety guidelines.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
EEG recording and power in alpha band	EEG recordings were acquired in a semi-dark, electrically shielded Faraday room using a BrainAmp 32-Channel DC System (Brain Products, Munich, Germany). Signals were sampled at 500 Hz with a 0.01-250 Hz bandpass filter and recorded using BrainVision Recorder software. A 32-channel Ag/AgCl electrode cap (Easycap) was positioned according to the international 10-20 system. Resting-state EEG data were collected for 4 minutes with eyes open and 4 minutes with eyes closed. Numerical evaluation of artifact-free EEG data for power density calculation is performed using Fast Fourier Transform (FFT) with 0.5 Hz frequency resolution, and alpha (8-13 Hz) bands were calculated and then averaged over these power spectrum values. The amplitude values, measured from peak to peak, were recorded for each individual, and the necessary data for statistical analysis were collected.	Before and immediately after applying tDCS
Cancellation Test	The Cancellation Test is one of the most widely used tools for assessing visuospatial attention. IT consists of four subtests arranged on A4-sized sheets. Each subtest includes 60 target stimuli distributed among 300 total stimuli. For each subtest, separate scores are calculated for the right and left sides, including the number of correctly marked targets (IT1), omitted targets (IT2), incorrectly marked letters/shapes (IT3), total error score (IT4), and scanning time (IT5). The total error score is calculated as the sum of omitted targets and incorrectly marked letters/shapes. Achieving a high score (i.e., a high number of correctly marked targets and a low number of errors) and a short completion time (time score) indicate better performance. İn the present study, the paper-and-pencil version of the Cancellation Test was chosen to reliably assess visuospatial attention and subtle tDCS-induced changes.	Before and immediately after applying tDCS

Collaborators and Investigators

• Sponsor: Medipol University
• Investigators: Study Director: Lütfü Hanoğlu, Professor, Medipol University; Study Chair: Mevhibe Sarıcaoğlu, PhD, Medipol University; Study Director: Miray Budak, PhD, Rutgers University-Newark; Study Chair: Fatma Aydın, MsC, Medipol University

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2021
• Primary Completion (Actual): July 1, 2021
• Study Completion (Actual): November 1, 2021

Study Registration Dates

• First Submitted: May 22, 2026
• First Submitted That Met QC Criteria: June 3, 2026
• First Posted (Actual): June 4, 2026

Study Record Updates

• Last Update Posted (Actual): June 4, 2026
• Last Update Submitted That Met QC Criteria: June 3, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: tDCS; visuospatial attention; posterior parietal cortex; EEG alpha oscillations
• Additional Relevant MeSH Terms: Therapeutics; Behavioral Disciplines and Activities; Electric Stimulation Therapy; Convulsive Therapy; Psychiatric Somatic Therapies; Electroshock; Psychological Techniques; Transcranial Direct Current Stimulation
• Other Study ID Numbers: E-10840098-772.02-605

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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