Ultrasonic neural stimulation of zebrafish larvae reveals region-specific calcium imaging activation patterns

Ultrasound (US) stimulation of neural activity has gained increasing attention in the scientific community, especially thanks to its advantages, first and foremost non-invasiveness. Little is known, however, about the relationship between the properties of the target neuronal populations and their responsiveness to this form of stimulation in vivo. Here, we report cortex-wide US-induced activity patterns of zebrafish larvae recorded through calcium imaging microscopy. We were able to induce a reliable neuronal activation monotonically increasing with applied pressure. As expected by previous results, activation probability grows with stimulus duration. Moreover, a spatial analysis of the responsiveness showed that it was highly area-specific, indicating a role of neuronal type and architecture in US sensitivity. Control experiments finally proved that sensory perception of US-induced water movements did not account for the whole neural activation, highlighting the role of direct neuronal stimulation. These results provide a frame for US studies on zebrafishes, characterizing the relationship between stimulation parameters and local responsiveness. Future studies will focus on the link between area-specific neuronal properties and US sensitivity to shed light on the biophysics of US neuromodulation.