The understanding of brain function and the capacity to treat neurological and psychiatric disorders rest on the ability to intervene in neuronal activity in specific brain circuits. Current methods of neuromodulation incur a tradeoff between spatial focus and the level of invasiveness. Transcranial focused ultrasound (FUS) is emerging as a neuromodulation approach that combines noninvasiveness with focus that can be relatively sharp even in regions deep in the brain. This may enable studies of the causal role of specific brain regions in specific behaviors and behavioral disorders. In addition to causal brain mapping, the spatial focus of FUS opens new avenues for treatments of neurological and psychiatric conditions. This review introduces existing and emerging FUS applications in neuromodulation, discusses the mechanisms of FUS effects on cellular excitability, considers the effects of specific stimulation parameters, and lays out the directions for future work.
Keywords: ARF = acoustic radiation force; DBS = deep brain stimulation; ECoG = electrocorticography; ET = essential tremor; FUS = focused ultrasound; TCS = transcranial current stimulation; TMS = transcranial magnetic stimulation; brain mapping; deep brain; neurointervention; neuroplasticity; noninvasive; stimulation.