Offline impact of transcranial focused ultrasound on cortical activation in primates.
Verhagen L., Gallea C., Folloni D., Constans C., Jensen DE., Ahnine H., Roumazeilles L., Santin M., Ahmed B., Lehericy S., Klein-Flügge MC., Krug K., Mars RB., Rushworth MF., Pouget P., Aubry J-F., Sallet J.
To understand brain circuits it is necessary both to record and manipulate their activity. Transcranial ultrasound stimulation (TUS) is a promising non-invasive brain stimulation technique. To date, investigations report short-lived neuromodulatory effects, but to deliver on its full potential for research and therapy, ultrasound protocols are required that induce longer-lasting 'offline' changes. Here, we present a TUS protocol that modulates brain activation in macaques for more than one hour after 40 s of stimulation, while circumventing auditory confounds. Normally activity in brain areas reflects activity in interconnected regions but TUS caused stimulated areas to interact more selectively with the rest of the brain. In a within-subject design, we observe regionally specific TUS effects for two medial frontal brain regions - supplementary motor area and frontal polar cortex. Independently of these site-specific effects, TUS also induced signal changes in the meningeal compartment. TUS effects were temporary and not associated with microstructural changes.