Inconsistent Effects of Parietal α-tACS on Pseudoneglect across Two Experiments: A Failed Internal Replication

Area of Science:

• Neuroscience
• Cognitive Science
• Neuromodulation

Background:

• Transcranial electrical stimulation (tES) is an emerging technique for modulating brain activity in clinical and research settings.
• Current tES applications face challenges including small effect sizes and significant inter-individual variability.
• Understanding the efficacy and reliability of different tES protocols is crucial for advancing the field.

Purpose of the Study:

• To compare the effects of two inhibitory tES techniques, alpha-frequency transcranial alternating current stimulation (α-tACS) and cathodal transcranial direct current stimulation (c-tDCS), on visuospatial attention.
• To investigate the reproducibility of tES effects by conducting a direct replication of the initial experiment.
• To assess the specificity of α-tACS by comparing it with a higher frequency (45 Hz) tACS protocol.

Main Methods:

• Two experiments involving 2x20 healthy participants performing a perceptual line bisection task.
• Application of three tES protocols: sham, α-tACS (10 Hz), and c-tDCS, targeting the right parietal cortex.
• Experiment 2 included an additional 45 Hz-tACS condition and aimed to replicate Experiment 1 findings.

Main Results:

• In Experiment 1, right parietal α-tACS induced a rightward shift in spatial attention bias, as predicted.
• This effect was not replicated in Experiment 2 or when analyzing the complete dataset.
• Neither c-tDCS nor 45 Hz-tACS demonstrated significant effects on spatial attention bias.

Conclusions:

• The initial finding for α-tACS was not robust, underscoring the critical need for replication studies in tES research.
• Results emphasize the importance of adequate statistical power and optimizing tES parameters for reliable outcomes.
• Further research is needed to establish the consistency and best practices for using tES interventions.