EEG, Posterior Parietal Cortex, tDCS, Visual Attention
Conditions
Keywords
tDCS, posterior parietal cortex, visuospatial attention, EEG alpha oscillations
Brief summary
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.
Interventions
DEVICEAnodal 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.
DEVICESham 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.
Sponsors
Medipol University
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| EEG recording and power in alpha band | Before and immediately after applying tDCS | 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. |
| Cancellation Test | Before and immediately after applying tDCS | 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. |
Countries
Turkey (Türkiye)
Contacts
STUDY_CHAIRMevhibe Sarıcaoğlu, PhD
Medipol University
STUDY_DIRECTORMiray Budak, PhD
Rutgers University-Newark
STUDY_CHAIRFatma Aydın, MsC
Medipol University
STUDY_DIRECTORLütfü Hanoğlu, Professor
Medipol University
Outcome results
None listed