Noninvasive Focused Ultrasound for Neuromodulation: A Review Paul Bowary, MD a, *, Benjamin D. Greenberg, MD, PhD a,b,c INTRODUCTION Focused ultrasound (FUS) has been of research and potential clinical interest as a neu- romodulation method for over half a century. 1–5 However, over the past decade the interest in this technique has increased dramatically. High-intensity focused ultra- sound (HIFU) is an approved technique for ablation of specific brain targets in the treatment of essential tremor 6,7 and chronic pain. Low-intensity focused ultrasound (LIFU) is unique among transcranial brain stimulation methods in combining excep- tional spatial resolution (on the millimeter scale) 8–10 with the potential to target subcor- tical structures (deeper than 10 cm) 11 through the intact skull. It also has potential for inducing neuronal excitation or suppression without evidence of tissue damage. 12 Recent studies have shown neuromodulation effects—when LIFU is administered in pulsation mode 13 —translated onto behavioral outcomes, 14–16 electrophysiologic Disclosure Statement: No disclosures. a The Department of Psychiatry and Human Behavior, Alpert Medical School, Brown University, Providence, RI 02906, USA; b Butler Hospital, 345 Blackstone Boulevard, Providence, RI 02906, USA; c VA RR&D Center for Neurorestoration and Neurotechnology, Providence VA Medical Center, Providence, RI 02908, USA * Corresponding author. E-mail address: paul_bowary@brown.edu KEYWORDS  FUS  LIFU  Pulsation  Neuromodulation  Neurostimulation KEY POINTS  Low-intensity focused ultrasound (LIFU) can be used for intermittent (pulsation) or contin- uous brain stimulation for neuromodulation.  LIFU is a potential alternative to other noninvasive neuromodulation techniques.  LIFU offers potential ability to excite or inhibit neural activity, exquisite spatial resolution, and feasible use with simultaneous MRI.  There remain substantial unanswered questions about the safety and efficacy of the tech- nique at this early stage of its development. Psychiatr Clin N Am - (2018) -–- https://doi.org/10.1016/j.psc.2018.04.010 psych.theclinics.com 0193-953X/18/ª 2018 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).