Electromagnetic-based methods of stimulating brain activity require invasive procedures
or have other limitations. Deep-brain stimulation requires surgically implanted electrodes.
Transcranial magnetic stimulation does not require surgery, but suffers from low spatial
resolution. Optogenetic-based approaches have unrivaled spatial precision, but require
genetic manipulation. In search of a potential solution to these limitations, we began
investigating the influence of transcranial pulsed ultrasound on neuronal activity
in the intact mouse brain. In motor cortex, ultrasound-stimulated neuronal activity
was sufficient to evoke motor behaviors. Deeper in subcortical circuits, we used targeted
transcranial ultrasound to stimulate neuronal activity and synchronous oscillations
in the intact hippocampus. We found that ultrasound triggers TTX-sensitive neuronal
activity in the absence of a rise in brain temperature (<0.01 degrees C). Here, we
also report that transcranial pulsed ultrasound for intact brain circuit stimulation
has a lateral spatial resolution of approximately 2 mm and does not require exogenous
factors or surgical invasion.
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