Non-invasive brain stimulation: current and future applications in neurology

Device-based non-invasive brain stimulation (NIBS) techniques show promise for the treatment of neurological and psychiatric disorders, although inconsistencies in protocol designs and study findings can make the field difficult to navigate. In this Review, we discuss applications of NIBS for enhancing cognitive and motor function in people with various neurological diseases that are characterized by disruption of large-scale brain networks, including neurodegenerative diseases and brain lesion disorders such as stroke and traumatic brain injury. In particular, we focus on repetitive transcranial magnetic stimulation and transcranial electrical stimulation, as these techniques have been widely used in clinical settings and randomized controlled trials. We summarize and synthesize current knowledge, and highlight gaps and shortcomings in the existing research that make it difficult to draw firm conclusions, including small sample sizes, heterogeneous patient populations and variations in stimulation protocols. We believe that a rapid evolution of NIBS techniques from state-dependent, network-informed, multifocal and subcortical paradigms to individualized electric field modelling and accelerated NIBS protocols will improve the management of neurological disorders. However, realizing this potential will require us to address crucial challenges and acquire deeper mechanistic insights, with the aim of developing adaptive, biomarker-driven protocols to optimize target engagement, dosing and timing for each patient.