Unipolar brush cells

Unipolar brush cells (UBCs) are a class of excitatory glutamatergic interneuron found in the granular layer of the cerebellar cortex and also in the granule cell domain of the cochlear nucleus. They were first described in 1977 by Altman and Bayer.

The UBC has a round or oval cell body with usually a single short dendrite that ends in a brushlike tuft of short dendrioles. These brush dendrioles form very large synaptic junctions. They work together with vestibular fibres to integrate signals involving the orientation of the head that modulates reflex behaviour. UBCs are plentiful in those regions linked to vestibular functions and in the vermis where they are further concentrated into specific domains. UBCs function to amplify inputs from the vestibular ganglia and nuclei by spreading and prolonging excitation within the granular layer. UBCs are intrinsically-firing neurons. The shape and size of neuron cell bodies determine their firing patterns.

The dendritic brush and the large endings of the axonal branches are involved in the formation of glomeruli. The UBC has one short dendrite where the granule cell has four or five. UBCs are particularly evident in the parafloccus and flocculus. They receive glutamatergic inputs on its dendritic brush from a single mossy fibre terminal in the form of a giant glutamatergic synapse and make glutamatergic synapses with granule cells and other UBCs.