Figure 1.

Information flow through the cerebellum. Information from extracerebellar structures enters the cerebellum via MFs (violet arrows) and climbing fibres (not shown). MFs contact both the cerebellar cortex and nuclei; in the former, they synapse in the granular layer, the first stage of information processing along this pathway. Here reside densely packed excitatory granule cells (in red), and sparsely distributed inhibitory Golgi cells (in blue), which inhibit vast and overlapping groups of granule cells. Interaction between these two neuronal populations determine how information is transmitted downstream to Purkinje cells (in orange) through granule cell ascending axons and parallel fibres (red fibres). Purkinje cells generate the sole output of the cerebellar cortex, influencing neural activity in the cerebellar nuclei (brown box). Nuclear neurons depart axons back to extracerebellar structures (brown arrows), also making collaterals that terminate as MFs in the granular layer. The dotted box inscribes all MF terminals in the cerebellum.