Magnetic actuation of otoliths allows behavioral and brain-wide neuronal exploration of vestibulo-motor processing in larval zebrafish

The vestibular system in the inner ear plays a central role in sensorimotor control by informing the brain about the orientation and acceleration of the head. However, most experiments in neurophysiology are performed using head-fixed configurations, depriving animals of vestibular inputs. To overcome this limitation, we decorated the utricular otolith of the vestibular system in larval zebrafish with paramagnetic nanoparticles. This procedure effectively endowed the animal with magneto-sensitive capacities: applied magnetic field gradients induced forces on the otoliths resulting in robust behavioral responses comparable to that evoked by rotating the animal by up to 25°. We recorded the whole-brain neuronal response to this fictive motion stimulation using light-sheet functional imaging. Experiments performed in unilaterally injected fish revealed the activation of a commissural inhibition between the brain hemispheres. This magnetic-based stimulation technique for larval zebrafish opens new perspectives to functionally dissect the neural circuits underlying vestibular processing and to develop multisensory virtual environments, including vestibular feedback. Highlights After injecting a ferrofluid into the inner ear of a larval zebrafish, the ear-stones can be actuated via magnetic forces. This method allows one to elicit vestibular-like behavioral responses without impairing physiological inner ear functions. It is compatible with brain-scale functional imaging and thus offers a promising avenue to investigate the neural underpinnings of vestibular-driven behaviors. eTOC Ferrofluid injection into zebrafish inner ear allows magnetic manipulation of ear-stones to evoke vestibular responses in static animals. This in vivo method is compatible with brain-scale imaging, offering a promising approach to investigate neural mechanisms underlying vestibular-driven behaviors.