Related Experiment Video
Updated: Oct 17, 2026
The Combination of Transcranial Alternating Current Stimulation and Electroencephalogram
Published on: October 10, 2025
Effects of individualized phase-amplitude-coupled transcranial alternating current stimulation on tinnitus and
Youngmin Na1, Nour Alsabbagh2, Jayce Woojin Baek1,3
1The Laboratory of Hearing, Balance, and Integrated Neuroscience, Hallym University College of Medicine, Chuncheon, Gangwon, Republic of Korea.
Introduction:
Chronic tinnitus is a prevalent and disabling condition that is frequently accompanied by domain-specific cognitive difficulties. Abnormal neural oscillations and disrupted cross-frequency coupling (CFC) have been implicated in its pathophysiology. This study investigated whether individualized phase-amplitude-coupled transcranial alternating current stimulation (tACS), tailored to each participant's individual alpha frequency (IAF), was associated with changes in tinnitus symptoms, cognition, and neurophysiological measures.
Methods:
In this prospective single-arm interventional study, 25 adults with chronic tinnitus (>6 months) were enrolled, and 21 completed the protocol. Participants received five sessions of individualized IAF-based phase-amplitude-coupled tACS at 2 mA for 20 min per session. Tinnitus outcomes included the Tinnitus Handicap Inventory (THI) and visual analog scale ratings of loudness (VAS-L) and annoyance (VAS-A). Cognitive performance was assessed using the Montreal Cognitive Assessment, Trail Making Tests A and B, Digit Span Tests forward and backward (DST-F/B), and Symbol Digit Modalities Test (SDMT). Electroencephalography-based spectral and CFC analyses were conducted in an artifact-free subgroup of 10 participants.
Results:
THI scores decreased significantly over the course of the intervention, whereas VAS-L and VAS-A showed no significant group-level changes. Cognitive performance improved across global cognition, processing speed, executive function, and working memory. Repeated-measures analyses demonstrated significant session effects for DST-F, DST-B, and SDMT. DST-B also showed a significant overall pre- to post-stimulation effect, whereas this effect was marginal for DST-F and absent for SDMT; no significant tACS × session interactions were observed. CFC analyses showed no significant pre- to post-stimulation changes after correction for multiple comparisons.
Conclusion:
Repeated individualized IAF-based phase-amplitude-coupled tACS was associated with reduced tinnitus-related functional impact and improvements in several cognitive measures, whereas subjective loudness and annoyance did not change significantly at the group level. No robust group-level CFC changes were detected. Given the single-arm design and absence of sham control, these findings are preliminary and do not establish treatment-specific or causal effects. Larger randomized sham-controlled studies are needed to determine efficacy and clarify underlying neurophysiological mechanisms.
