Repeated application of bifocal transcranial alternating current stimulation (tACS) improves network connectivity and driving performance: a double-blind sham control study
DOI: 10.1101/2025.02.07.636997
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Summary
This study investigates whether repeated application of bifocal transcranial alternating current stimulation (tACS) can induce lasting improvements in functional connectivity and cognitive performance, specifically response inhibition and driving safety. While prior research has demonstrated within-session benefits of tACS on inhibitory control, there is a lack of evidence regarding the long-term retention of these effects, which is critical for clinical applicability. The authors aimed to determine if multiple sessions of bifocal tACS targeting the right inferior frontal gyrus (rIFG) and pre-supplementary motor area (preSMA)—key regions in the inhibitory control network—could enhance functional connectivity between these areas and translate to improved performance in both laboratory-based tasks and simulated driving. The study employed a double-blind, sham-controlled design with 30 young adults randomly assigned to either an active tACS or sham group. Participants underwent five stimulation sessions over two weeks. The active group received 20-minute sessions of 20 Hz beta-frequency bifocal tACS with a 0° phase alignment, while the sham group received ramped-up and down currents. Response inhibition was assessed using a stop-signal task (SST) administered throughout the sessions. Functional connectivity between the rIFG and preSMA was measured via resting-state electroencephalography (EEG) using imaginary coherence, recorded at baseline, post-intervention, and at a 7-day follow-up. Additionally, participants completed simulated driving tasks, including a braking task and a general driving task with a detection response task (DRT) to measure spare attentional capacity, before the first session and one day after the final session. The results indicated that repeated bifocal tACS significantly improved functional connectivity between the rIFG and preSMA in the active group across sessions, an effect that persisted at the 7-day follow-up. However, no significant changes were observed in response inhibition as measured by the stop-signal task, nor were there improvements in the specific braking task performance. Notably, general driving performance improved in the tACS group; participants demonstrated closer adherence to the speed limit and exhibited greater spare attentional capacity, as evidenced by faster and more accurate responses to peripheral targets during the DRT. These findings suggest that while the stimulation did not directly alter basic inhibitory reaction times, it enhanced broader cognitive resources relevant to complex, real-world tasks. The significance of this study lies in its demonstration that repeated bifocal tACS can produce sustained enhancements in cortical network connectivity, which may facilitate improved performance in ecologically valid tasks like driving. The dissociation between laboratory-based inhibitory measures and driving performance suggests that tACS may improve higher-order executive functions or attentional allocation rather than simple motor inhibition. These results support the potential of repeated tACS protocols as a non-invasive intervention for conditions characterized by impaired cortical connectivity and executive dysfunction, offering a promising avenue for improving safety and cognitive function in daily activities.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-08-09 |
| archive | success | canonical_url | — | — | 1 | 2026-08-09 |
| extract | success | pdftotext | — | — | 4 | 2026-08-10 |
| clean | success | clean | — | — | 2 | 2026-08-10 |
| chunk | success | chunk | — | — | 2 | 2026-08-10 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 2 | 2026-08-10 |
| promote | success | — | — | — | 1 | 2026-08-09 |
| summarize | success | llm | qwen3.6-27b-nvidia | summ-v5 | 2 | 2026-08-10 |
| tag | success | vector_similarity | — | — | 17 | 2026-08-11 |
| verify | success | — | — | — | 1 | 2026-08-10 |
Summary generated by qwen3.6-27b-nvidia on 2026-08-10; verification: verified.
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- Empirical Findings: physiological data