Climbing fiber multi-innervation of mouse Purkinje dendrites with arborization common to human

Canonically, each Purkinje cell in the adult cerebellum receives only one climbing fiber from the inferior olive. Underlying current theories of cerebellar function is the notion that this highly conserved one-to-one relationship renders Purkinje dendrites into a single computational compartment. However, we show that multiple primary dendrites are a near-universal morphological feature in humans. Using tract-tracing, immunolabeling, and in vitro electrophysiology, we demonstrate in mice that ~25% of mature polydendritic cells receive more than one climbing fiber input. Two-photon calcium imaging in vivo reveals that separate dendrites can exhibit distinct response properties to sensory stimulation, indicating some polydendritic cells integrate functionally independent climbing fiber receptive fields. These findings reveal that Purkinje cells are morphologically and functionally more diverse than previously thought.