A systematic review on multifocal non-invasive brain stimulation on motor function enhancement

Background Multifocal non-invasive brain stimulation (NIBS) has been highlighted as a promising approach for modulating motor functions by simultaneously stimulating several brain areas. However, the effectiveness and underlying mechanisms of this technique are still not well understood. Objective To evaluate the effectiveness of multifocal NIBS in promoting motor recovery, considering the targeted brain regions, stimulation protocols, and both behavioral and neurophysiological outcomes. Methods We conducted a systematic search of the PubMed, EMBASE, Cochrane Library, Scopus, and Web of Science databases up to February 10, 2025, adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. The inclusion criteria encompassed human studies utilizing concurrent dual-site or multifocal NIBS with pre- and post-intervention behavioral assessments. Studies on deep brain stimulation, corticocortical paired associative stimulation, sequential stimulation, case reports, and reviews were excluded. Results Out of 1,453 initial records, 9 studies met the inclusion criteria. These studies primarily focused on stimulating the dorsolateral prefrontal cortex and primary motor cortex. Neurophysiological data obtained from electroencephalography and functional magnetic resonance imaging indicated network-level modulations. Behavioral outcomes were variable, with some studies showing improvements in response inhibition, and motor learning, while others found no significant differences compared to sham stimulation. Conclusion While multifocal NIBS shows promise as a novel therapeutic approach, its efficacy remains uncertain due to variations in study designs, small sample sizes, and inconsistent results. Future research should focus on larger sample size, multi-arm trials and inclusion of neurophysiological biomarkers. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420250646196 , identifier: CRD420250646196.