Alpha transcranial alternating current stimulation as add-on to neglect training: a randomised trial

Abstract

Abstract Visuospatial neglect is a common and debilitating condition following unilateral stroke, significantly impacting cognitive functioning and daily life. There is an urgent need for effective treatments that can provide clinically relevant and sustained benefits. In addition to traditional stroke treatment, non-invasive brain stimulation, such as transcranial alternating current stimulation (tACS), shows promise as a complementary approach to enhance stroke recovery. In the current study, we aimed to evaluate the additive effects of multi-session tACS at alpha frequency when combined with visual scanning training in chronic stroke patients with visuospatial neglect. In this double-blind randomised controlled trial, we compared the effects of active tACS at alpha frequency to sham (placebo) tACS, both combined with visual scanning training. Both groups received eighteen 40-minute training sessions over a six-week period. A total of twenty-two chronic visuospatial neglect patients participated in the study (active group n = 12, sham group n = 10). The median age was 61.0 years, with a median time since stroke of 36.1 months. We assessed the patients at six time-points: at baseline, after the first, ninth, and eighteenth training sessions, as well as one week and three months following the completion of the combined neuromodulation intervention. The primary outcome measure was the change in performance on a visual search task, specifically the Star Cancellation Task. Secondary outcomes included performance on a visual detection task, two line bisection tasks, and three tasks evaluating visuospatial neglect in daily living. We found significantly improved visual search (primary outcome) and visual detection performance in the neglected side in the active tACS group, compared to the sham tACS group. We did not observe stimulation effects on line bisection performance nor in daily living. Time effects were observed on all but one outcome measures. Multi-session tACS combined with visual scanning training may be a more effective treatment for chronic visuospatial neglect than visual scanning training alone. These findings provide valuable insights into novel strategies for stroke recovery, even long after the injury, with the aim of enhancing cognitive rehabilitation outcomes and improving the overall quality of life for individuals affected by this condition.