They were first identified as inhibitory by Eccles et al. in 1964.  It was also the first example of an inhibitory feed back network, where the inhibitory interneuron was identified anatomically. These cells synapse onto the dendrite of granule cells and unipolar brush cells. They receive excitatory input from mossy fibres, also synapsing on granule cells, and parallel fibers, which are long granule cell axons.