Fig. 1.

Circuitry of the cerebellum and synaptic action of the climbing fibers. a Canonical circuitry of the cerebellum including climbing fiber–Purkinje cell circuit, mossy fiber-granule cell-parallel fiber–Purkinje cell circuit and Purkinje cell projection to the cerebellar nuclei. “+” and “-” denote excitatory and inhibitory synapses, respectively (modified with permission from [31]). b Top panel: intracellular recording from a Purkinje cell of both a complex spike (CS) with its initial Na⁺ spike and prolonged depolarization and a spontaneous simple spike SS (modified with permission from [12]). Bottom panel: extracellular recording from a Purkinje cell shows the high-frequency SS firing and low-frequency CS discharge (red dots) (modified with permission from [61]). c Spatial profile of Ca²⁺ influx evoked by climbing fiber input displaying Ca²⁺ transients at multiple locations along the dendritic tree (modified with permission from [61])