"Spike trains transfer information to and from neurons. Most studies so far assume that the average firing rate or “rate coding” is the predominant way of information coding. However, spikes occur at millisecond precision, and their actual timing or “temporal coding” can in principle strongly increase the information content of spike trains. The two coding mechanisms are not mutually exclusive. Neurons may switch between rate and temporal coding, or use a combination of both coding mechanisms at the same time, which would increase the information content of spike trains even further. Here, we propose to investigate the hypothesis that temporal coding plays, next to rate coding, important and specific roles in cerebellar processing during learning. The cerebellum is ideal to study this timely topic, because it has a clear anatomy with well-organized modules and matrices, a well-described physiology of different types of neurons with distinguishable spiking activity, and a central role in various forms of tractable motor learning. Moreover, uniquely in the brain, the main types of neurons in the cerebellar system can be genetically manipulated in a cell-specific fashion, which will allow us to investigate the behavioural importance of both coding mechanisms following cell-specific interference and/or during cell-specific visual imaging. Thus, for this proposal we will create conditional mouse mutants that will be subjected to learning paradigms in which we can disentangle the contributions of rate coding and temporal coding using electrophysiological and optogenetic recordings and stimulation. Together, our experiments should elucidate how neurons in the brain communicate during natural learning behaviour and how one may be able to intervene in this process to affect or improve procedural learning skills."