Noninvasive ultrasound alters neuronal activity in the awake mammalian brain
Embargo Date
2025-05-23
OA Version
Citation
Abstract
Transcranial pulsed ultrasound noninvasively activates individual neurons and neural circuits in the brain, providing promise as a neuromodulation therapy. While ultrasound’s fundamental frequency and intensity influence neuromodulation efficacy, it is unclear whether temporal patterning contributes to its neural effect. Given that intrinsic neuronal activity is limited to a couple hundred hertz and often exhibits frequency preference, different subsets of neurons may respond to ultrasound delivered at pulse repetition frequencies (PRFs) in the physiologic range. In this dissertation, we use optical imaging techniques to capture cellular responses to 0.35 MHz ultrasound at multiple PRFs with high spatiotemporal precision in awake mice. First, we performed calcium imaging of individual motor cortex neurons, while delivering ultrasound at PRFs of 10, 40, or 140 Hz and compared these responses to the supra-physiologic PRF of 2 kHz. We next investigated cell type and PRF-specific effects of ultrasound pulsed at 10, 40, and 140 Hz using calcium imaging in transgenic mice with fluorescently tagged parvalbumin-positive interneurons. Most neurons were preferentially activated by only one of the three PRFs, highlighting unique cellular effects of physiologic PRFs. Finally, using voltage imaging we discovered that ultrasound induces prominent spiking and membrane depolarization with a latency shorter than 18 ms. Ultrasound also paced membrane voltage at the stimulation PRF, leading to prominent entrainment in many neurons. Together, these findings provide first direct experimental evidence that noninvasive ultrasound pulsed at physiologically relevant frequencies can selectively, reversibly, and directly activate neuronal subsets and entrain cellular dynamics, highlighting a novel strategy to engage and tune neural circuits for clinical applications.
Description
License
Attribution-NonCommercial 4.0 International