AUTHOR=Toth Jake , Kurtin Danielle Lauren , Brosnan Méadhbh , Arvaneh Mahnaz TITLE=Opportunities and obstacles in non-invasive brain stimulation JOURNAL=Frontiers in Human Neuroscience VOLUME=Volume 18 - 2024 YEAR=2024 URL=https://www.frontiersin.org/journals/human-neuroscience/articles/10.3389/fnhum.2024.1385427 DOI=10.3389/fnhum.2024.1385427 ISSN=1662-5161 ABSTRACT=Non-invasive brain stimulation (NIBS) is a complex and multifaceted approach to modulating brain activity and holds the potential for broad accessibility. This work discusses the mechanisms of the four distinct approaches to modulating brain activity non-invasively: electrical currents, magnetic fields, light, and ultrasound. We examine the dual stochastic and deterministic nature of brain activity and its implications for NIBS, highlighting the challenges posed by interindividual variability, nebulous dose-response relationships, potential biases and neuroanatomical heterogeneity. Looking forward, we propose five areas of opportunity for future research: closedloop stimulation, consistent stimulation of the intended target region, reducing bias, multimodal approaches and strategies to address low sample sizes.