Causal Mechanisms of Odor-Guided Behavior in Humans

Study Description: Primary olfactory cortex has been implicated in a variety of odorguided behaviors in both animal models and humans. However, direct causal evidence for the functional role of different primary olfactory regions in humans is currently missing, due to the lack of non-invasive neuromodulation methods that can effectively target deep brain regions. With the recent advancement of transcranial focused ultrasound stimulation (TUS), this challenge can now be overcome. The goal of this protocol is to use TUS to temporarily modulate activity in primary olfactory cortex and thereby assess its contribution to olfactory function. Objectives: The primary objective is to determine the causal contribution of primary olfactory brain regions to olfactory functions. The secondary objective is to 1) evaluate the neural mechanisms by which these brain regions support these olfactory functions, and 2) assess the safety profile of TUS. Endpoints: The primary endpoint is to determine if TUS of olfactory cortices alters olfactory function. The secondary endpoints are to 1) evaluate whether TUS changes neural activity in olfactory regions and 2) assess the degree to which TUS elicits unwanted side effects in healthy adult participants.