Work

Effects of individualized phase-amplitude-coupled transcranial alternating current stimulation on tinnitus and cognition

Year: 2026

Type: article

Abstract: 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.

Source: Frontiers in Neuroscience

DOI: 10.3389/fnins.2026.1905125