Offline impact of transcranial focused ultrasound on cortical activation in primates

Abstract

To understand brain circuits it is necessary both to record and manipulate their activity. Despite increased availability of techniques for manipulating neural activity in rodents, manipulating neural activity in primates remains difficult. Here we show that a minimally invasive technique, transcranial focused ultrasound stimulation (TUS), induced offline changes to activity of circumscribed brain regions in the macaque. Applying TUS to the supplementary motor area or frontal polar cortex resulted in spatially specific patterns of activity change measurable with functional magnetic resonance imaging. In each case changes reflected each areas known network of interactions with the rest of the brain. Independent of these specific neural effects, TUS over these regions also induced widespread signal changes that might have a non-neuronal origin possibly mediated by the cerebral spinal fluid compartment. Although sustained for more than one hour beyond the 40s stimulation period, TUS effects were reversible and not associated with histological changes.\n\nHighlights O_LIMany studies of ultrasound neuromodulation focus on online effects in rodents.\nC_LIO_LIWe use fMRI connectivity to investigate its offline impact in the primate brain.\nC_LIO_LI40 s of ultrasound leads to a sustained, specific, reversible neural modulation.\nC_LIO_LIUltrasound caused a sharpening of the stimulated regions connectivity profile.\nC_LI\n\nIn BriefA new application of focused ultrasound safely modulates brain activation in primates for up to 2 hours after 40 seconds of stimulation. Ultrasound caused the stimulated area to interact more selectively with the rest of the brain.