Direct translation of climbing fiber burst-mediated sensory coding into post-synaptic Purkinje cell dendritic calcium
Seung‐Eon Roh, Seung Ha Kim, Changhyeon Ryu, Chang-Eop Kim, Yong Gyu Kim, Paul F. Worley, Sun Kwang Kim, Sang Jeong Kim
Abstract
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.