Grégory C. Nordmann, Spencer D. Balay, Thamari Neranjana Kapuruge, Marco Numi, Christoph Leeb, Simon Nimpf, E. Pascal Malkemper, Lukas Landler, David A. Keays
How animals detect Earth’s magnetic field remains a mystery in sensory biology. Despite extensive behavioral evidence, the neural circuitry and molecular mechanisms responsible for magnetic sensing remain elusive. Adopting an unbiased approach, we used whole-brain activity mapping, tissue clearing, and light sheet microscopy to identify neuronal populations activated by magnetic stimuli in the pigeon ( Columba livia ). We demonstrate robust, light-independent bilateral neuronal activation in the medial vestibular nuclei and the caudal mesopallium. Single-cell RNA sequencing of the semicircular canal cristae revealed specialized type II hair cells that express the molecular machinery necessary for the detection of magnetic stimuli by electromagnetic induction. Our data support a model whereby electromagnetic input from the semicircular canals activates a vestibular-mesopallial circuit in the pigeon brain.