Study of LIFU on fMRI pain signals. Participants receive low-intensity focused ultrasound (LIFU) and fMRI scans to measure changes in both resting and heat pain signals. Physiology may also be measured. Questionnaires and symptom monitoring will take place. The study takes place over 4 study visits.

Study aims to examine the effects of noninvasive brain stimulation on brain signals. This insight may have potential clinical implications for addiction, pain, and mental health populations. Participants will receive MRI and CT imaging. Participants receive low-intensity focused ultrasound (LIFU) to temporarily change brain activity. Participants then receive fMRI scans to measure changes in both resting and heat evoked brain signaling using a quantitative sensory testing device. Heart rate, blood pressure, respiratory rate, and skin moisture is monitored. Participants complete a battery of questionnaires, both behavioral and symptom monitoring. The study takes place over 4 study visits.

Inclusion Criteria:

• Healthy volunteers, all ethnicities, who understand and speak English.

Exclusion Criteria:

Claustrophobia (scanning environment may be uncomfortable). Contraindications to MRI: including pacemaker, aneurysm clips, neurostimulators, cochlear implants, metal in eyes, steel worker, or other implants.

Contraindications to CT: pregnancy Active medical disorder or treatment with potential CNS effects (e.g. Alzheimer's) History of neurologic disorder. (e.g. Parkinson's, Epilepsy, or Essential Tremor) History of head injury resulting in loss of consciousness for >10 minutes. History of alcohol or drug dependence (through self-report).