Multifocal transcranial electrical stimulation to enhance cognitive functions: a systematic review

Area of Science:

• Neuroscience
• Cognitive Science
• Neuromodulation

Background:

• Multifocal transcranial Electrical Stimulation (tES) concurrently targets multiple brain regions to modulate cognitive functions.
• The precise efficacy and underlying mechanisms of multifocal tES remain incompletely understood.

Purpose of the Study:

• To systematically evaluate the efficacy of multifocal tES in enhancing cognitive function.
• To examine the impact of multifocal tES by analyzing targeted brain regions, stimulation protocols, and resulting behavioral and neurophysiological outcomes.

Main Methods:

• A systematic literature search was performed across major databases (PubMed, EMBASE, Cochrane, Scopus, Web of Science) up to February 10, 2025.
• Included studies involved concurrent dual-site or multifocal tES in humans with pre- and post-intervention behavioral assessments.
• Exclusion criteria covered deep brain stimulation, sequential stimulation, case reports, and reviews, adhering to PRISMA 2020 guidelines.

Main Results:

• Fourteen studies met the inclusion criteria from an initial 1,453 records.
• Transcranial direct current stimulation/transcranial alternating current stimulation targeting the frontoparietal network was common.
• Neuroimaging (EEG, fMRI) indicated network-level modulations, but behavioral outcomes were inconsistent, with some showing cognitive improvements and others no significant effects compared to sham.

Conclusions:

• The efficacy of multifocal tES is currently difficult to ascertain due to heterogeneous study designs, small sample sizes, and conflicting results.
• Future research should focus on multi-arm trials, neurophysiological biomarkers, and personalized stimulation protocols to optimize multifocal tES effectiveness.