Neuromodulation for Brain Disorders: Challenges and Opportunities

The field of neuromodulation encompasses a wide spectrum of interventional technologies that modify pathological activity within the nervous system to achieve a therapeutic effect. Therapies including deep brain stimulation (DBS), intracranial cortical stimulation (ICS), transcranial direct current stimulation (tDCS), and transcranial magnetic stimulation (TMS) have all shown promising results across a range of neurological and neuropsychiatric disorders. While the mechanisms of therapeutic action are invariably different amongst these approaches, there are several fundamental neuroengineering challenges that are commonly applicable to improving neuromodulation efficacy. This article reviews the state-of-the-art of neuromodulation for brain disorders and discusses the challenges and opportunities available for clinicians and researchers interested in advancing neuromodulation therapies. While neuromodulation approaches have been adopted as standard treatments in clinical practice, their mechanisms of action have not yet been fully elucidated. Challenges remain in dissecting the spatio-temporal neurophysiological changes that occur during and following neuromodulation therapies, especially as they relate to changes in behavior. Engineering challenges exist to develop more efficient neuromodulation techniques including electric and magnetic, as well as optogenetic approaches, patient-specific computational models, closed-loop algorithms for more efficient therapy titration, and batteries with longer lifetimes all have potential to improve therapeutic efficacy while reducing side effects and surgical complications. Additionally, the field of neuromodulation will benefit from randomized controlled trials that delineate the settings used in stimulation and how those parameters relate to patient anatomy.