The adult mammalian cerebellar cortex is generally assumed to have a uniform cytoarchitecture. Differences in cerebellar function are thought to arise, in the main, through distinct patterns of input and output connectivity, rather than as a result of variations in cortical microcircuitry. However, evidence from anatomical, physiological and genetic studies is increasingly challenging this orthodoxy and there are now various lines of evidence that the cerebellar cortex is non uniform. Here we develop the hypothesis that regional differences in cerebellar cortical microcircuit properties lead to important differences in information processing