Transcranial focused ultrasound: a new tool for non-invasive neuromodulation

Ultrasound (US) is widely known for its utility as a biomedical imaging modality. An abundance of evidence has recently accumulated showing that US is also useful for non-invasively modulating brain circuit activity. Through a series of studies discussed in this short review, it has recently become recognized that transcranial focused ultrasound can exert mechanical (non-thermal) bioeffects on neurons and cells to produce focal changes in the activity of brain circuits. In addition to highlighting scientific breakthroughs and observations that have driven the development of the field of ultrasonic neuromodulation, this study also provides a discussion of mechanisms of action underlying the ability of ultrasound to physically stimulate and modulate brain circuit activity. Exemplifying some forward-looking tools that can be developed by integrating ultrasonic neuromodulation with other advanced acoustic technologies, some innovative acoustic imaging, beam forming, and focusing techniques are briefly reviewed. Finally, the future outlook for ultrasonic neuromodulation is discussed, specifically in the context of applications employing transcranial focused ultrasound for the investigation, diagnosis, and treatment of neuropsychiatric disorders.