A novel inhibitory nucleo-cortical circuit controls cerebellar Golgi cell activity

The cerebellum is a region in the brain that plays a central role in controlling posture and movement. The cerebellum is composed of a cortex and several nuclei. The nuclei are thought to ‘compute’ the signals that are sent from the cerebellum to other parts of the brain to control posture and movement. They do this under the supervision of the cortex. The main interaction between the cortex and the nuclei involves cortical neurons called Purkinje cells inhibiting the activity of the nuclei. Ankri, Husson et al. have now used various genetic techniques and mutant mice to identify a new population of neurons in the nuclei of the cerebellum and to express fluorescent markers into these cells. This approach reveals that the axons of these neurons ‘climb’ from the nuclei to the cortex to form a new circuit called the inhibitory nucleo-cortical (iNC) pathway. Moreover, activating the iNC axons with light reveals that they selectively target and silence a population of neurons called the Golgi cells, which control the transmission of information in the cerebellar cortex. Ankri, Husson et al. go on to show that the Golgi cells silenced by the iNC pathway differ from other Golgi cells in a number of ways: in particular, these Golgi cells use a chemical called GABA to communicate with neurons. The next challenge is to explore how the iNC pathway fine-tunes how sensory inputs are processed in the cerebellum, and to better understand its role in the execution of complex movements, including in people with conditions that affect motor function, such as ataxias.