  Low-intensity ultrasonic waves can remotely and nondestructively excite
central nervous system (CNS) neurons. While diverse applications for this
effect are already emerging, the biophysical transduction mechanism underlying
this excitation remains unclear. Recently, we suggested that ultrasound-induced
intramembrane cavitation within the bilayer membrane could underlie the
biomechanics of a range of observed acoustic bioeffects. In this paper, we show
that, in CNS neurons, ultrasound-induced cavitation of these nanometric bilayer
sonophores can induce a complex mechanoelectrical interplay leading to
excitation, primarily through the effect of currents induced by membrane
capacitance changes. Our model explains the basic features of CNS
acoustostimulation and predicts how the experimentally observed efficacy of
mouse motor cortical ultrasonic stimulation depends on stimulation parameters.
These results support the hypothesis that neuronal intramembrane
piezoelectricity underlies ultrasound-induced neurostimulation, and suggest
that other interactions between the nervous system and pressure waves or
perturbations could be explained by this new mode of biological piezoelectric
transduction.
