Direct translation of climbing fiber burst-mediated sensory coding into post-synaptic Purkinje cell dendritic calcium

Climbing fibers (CFs) generate complex spikes (CS) and Ca(2+) transients in cerebellar Purkinje cells (PCs), serving as instructive signals. The so-called 'all-or-none' character of CSs has been questioned since the CF burst was described. Although recent studies have indicated a sensory-driven enhancement of PC Ca(2+) signals, how CF responds to sensory events and contributes to PC dendritic Ca(2+) and CS remains unexplored. Here, single or simultaneous Ca(2+) imaging of CFs and PCs in awake mice revealed the presynaptic CF Ca(2+) amplitude encoded the sensory input’s strength and directly influenced post-synaptic PC dendritic Ca(2+) amplitude. The sensory-driven variability in CF Ca(2+) amplitude depended on the number of spikes in the CF burst. Finally, the spike number of the CF burst determined the PC Ca(2+) influx and CS properties. These results reveal the direct translation of sensory information-coding CF inputs into PC Ca(2+), suggesting the sophisticated role of CFs as error signals.