Abstract
Transcranial focused ultrasound (FUS) is making progress as a new non-invasive mode of regional brain stimulation. Current evidence of FUS-mediated neurostimulation for humans has been limited to the observation of subjective sensory manifestations and electrophysiological responses, thus warranting the identification of stimulated brain regions. Here, we report FUS sonication of the primary visual cortex (V1) in humans, resulting in elicited activation not only from the sonicated brain area, but also from the network of regions involved in visual and higher-order cognitive processes (as revealed by simultaneous acquisition of blood-oxygenation-level-dependent functional magnetic resonance imaging). Accompanying phosphene perception was also reported. The electroencephalo graphic (EEG) responses showed distinct peaks associated with the stimulation. None of the participants showed any adverse effects from the sonication based on neuroimaging and neurological examinations. Retrospective numerical simulation of the acoustic profile showed the presence of individual variability in terms of the location and intensity of the acoustic focus. With exquisite spatial selectivity and capability for depth penetration, FUS may confer a unique utility in providing non-invasive stimulation of region-specific brain circuits for neuroscientific and therapeutic applications.
Highlights
Transcranial focused ultrasound (FUS) is making progress as a new non-invasive mode of regional brain stimulation
We used a similar pulsing scheme that had previously resulted in the successful stimulation of the SI in humans[17] and animals[10,14]: sonication duration of 300 ms with a tone burst duration (TBD) of 1 ms repeated at a pulse repetition frequency (PRF) of 500 Hz
After aligning the acoustic focus to the V1 in reference to the individual-specific functional data and skull neuroanatomy, FUS was applied to the V1 through a polyvinyl alcohol (PVA) hydrogel[21], which was compressed to ~1 cm thickness around the contour of the skin, achieved tight acoustic coupling while maintaining the orientation of the sonication entry as perpendicular as possible to the scalp (Fig. 1d)
Summary
Transcranial focused ultrasound (FUS) is making progress as a new non-invasive mode of regional brain stimulation. Advancements in FUS technology enable the transcranial delivery of the acoustic energy to highly-localized areas (on the order of a few millimeters) across the brain, including deep brain structures[4,5,6]. This ability has been utilized to thermally ablate a specific brain region using high acoustic intensity in the context of functional neurosurgery[4,6]. With its superior spatial selectivity and its feasibility for use in humans, transcranial FUS is gaining momentum as a new mode of non-invasive brain stimulation that may provide new opportunities in the assessment of normal and aberrant region-specific brain functions as well as in the development of various modes of neurotherapeutics.
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