We propose to develop focused ultrasound (FUS) for deep brain stimulation (DBS.) DBS is a proven therapy for movement disorders and holds considerable promise for psychiatric conditions such as medically intractable depression. The main drawback of electrical DBS is that it is highly invasive. Non-invasive methods, such as transcranial magnetic or direct current stimulation (TMS and TDCS) have limited penetrability to reach deep brain structures. Is a novel approach that uses focused ultrasound (FUS) to reach any brain structure and directly stimulate or inhibit neurons in the targeted region. The method is non-invasive, but spatially and temporally precise. It has been hypothesized that FUS interacts with ion-channel coupled mechanoreceptors that occur naturally in the targeted brain region. We have recently shown that FUS can improve performance on a decision-making task in monkeys. Here, we propose to study the mechanism underlying this effect by varying FUS frequency and pressure in awake monkeys trained to make evidence and reward based decisions, and in anesthetized monkeys undergoing fMRI. We will also test whether FUS enhances the efficacy of neuroactive drugs. FUS could provide a new research tool for establishing causal brain-behavior relationships and mapping neural circuits in healthy humans. It also provides a novel method for introducing neuroactive drugs that do no cross the intact BBB, or enhancing the effect of drugs that do cross the BBB. The development of sonogenetics could make deep brain stimulation available for patients who are not candidates for surgical approaches. Our approach incorporates safety controls to demonstrate that neural and behavioral effects of FUS or FUS+microbubbles are not due to edema, hemorrhage, lesions or thermal effects.The proposed experiments are essential for establishing the efficacy of focused ultrasound deep brain stimulation to treat psychiatric illnesses that affect cognition and motivation. To reap these benefits, it is necessary to determine the behavioral effects of FUS alone or in combination with other factors such as microbubbles. We are currently the only group currently developing this approach in the basal ganglia of awake, behaving monkeys as well as examining the FUS technique with and without microbubbles in order to exploit its full scope.