Transcranial Brain Stimulation: Technical, Computational, and Clinical Aspects in Contemporary Research

This article provides a narrative review of the technical, computational and clinical aspects of transcranial brain stimulation (TBS), with an emphasis on transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). The review addresses three central questions: which physical, engineering, and biological principles determine the generation, propagation, and focality of electromagnetic fields in the human head. The second question asks how modeling approaches, stimulation parameters, and hardware design influence the accuracy, safety, and individual variability of brain stimulation. And, finally, how these technical factors translate into current clinical applications, therapeutic efficacy, and practical limitations. The key take-home messages are as follows: for engineers, realistic anatomical head models, precise coil/electrode placement, and reliable numerical solvers remain essential for predicting field distribution and optimizing stimulation protocols; for clinicians, stimulation outcomes are strongly dependent on anatomy-specific field patterns, safety constraints, and device-related parameters that require careful adjustment; and for both groups, despite significant technological progress, effective and reproducible stimulation still demands systematic protocol refinement and individualized planning. Overall, this review integrates contemporary technical knowledge with clinical perspectives to support evidence-based use and future development of TMS and tDCS.