{
  "id": 8980274,
  "title": "Phase-lag-dependent modulation of interhemispheric β-band functional connectivity by dual-site tACS",
  "url": "https://urgent.news/2026/09/21/phase-lag-dependent-modulation-of-interhemispheric-band-functional",
  "topic": "science",
  "section": "Science",
  "published": "2026-09-21T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.09.14.751522v1?rss=1"
  },
  "original_language": "en",
  "account": "Dual-site transcranial alternating current stimulation (ds-tACS) is an experimental technique that aims to influence the interaction between the two hemispheres of the brain. Researchers have wondered how different timing adjustments, known as phase-lags, affect functional connectivity (FC), the level of communication between brain regions. To address this question, the study enrolled 29 healthy individuals, with 23 participating in the final analysis. The participants received 20 Hz ds-tACS targeted at their primary motor cortices on both sides of the brain, employing four different phase-lags (0, pi/2, pi, and 3pi/2), alongside sham stimulation, and had their high-density EEG recordings taken before and after the stimulation.\n\nThe researchers measured interhemispheric FC using the debiased weighted phase-lag index, which compares the timing of neural activity between the two hemispheres. Contrary to expectations, the overall changes in FC did not differ significantly between the active stimulation and sham conditions. However, the phase-lag that led to the largest absolute changes in FC varied greatly among participants. This prompted the researchers to evaluate the effect of phase-lag on FC using the Kullback-Leibler distance (DKL), a statistical measure of how one probability distribution diverges from a second, expected probability distribution. They found a significant phase-lag-dependent modulation of FC, which was brief, lasting only the first 5 seconds after stimulation, and confined to a narrow frequency range around the stimulation frequency (18-22 Hz). Importantly, this modulation occurred independently of any changes in the spectral power of brainwaves.\n\nTo further examine the relationship between phase, frequency, and FC, the researchers conducted an exploratory analysis. They discovered that the magnitude of the modulation varied quadratically with the individual's beta peak frequency, the specific frequency at which the brain exhibits the strongest connectivity. Participants whose beta peak frequencies were farther from the 20 Hz stimulation frequency experienced more substantial effects. These findings highlight that ds-tACS can induce a time- and frequency-specific modulation of interhemispheric FC across different phase-lags. Given the association between individual beta peak connectivity frequency and the phase-lag associated with the maximum FC change, the study suggests that personalized neuromodulation protocols could benefit from considering these factors when designing treatment strategies.",
  "summary": "Dual-site transcranial alternating current stimulation (ds-tACS) is a promising tool for causally manipulating interhemispheric communication; nevertheless, how different stimulation phase-lags selectively modulate functional connectivity (FC) remains unclear. We recruited 29 healthy participants and included 23 in the final analyses. Participants received 20 Hz ds-tACS over the bilateral primary…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}