Stellate cell computational modeling predicts signal fltering in the molecular layer circuit of cerebellum

Abstract

The functional properties of cerebellar stellate cells and the way they regulate molecular layer activity are still unclear. We have measured stellate cells electroresponsiveness and their activation by parallel fber bursts. Stellate cells showed intrinsic pacemaking, along with characteristic responses to depolarization and hyperpolarization, and showed a marked short-term facilitation during repetitive parallel fber transmission. Spikes were emitted after a lag and only at high frequency, making stellate cells to operate as delay-high-pass flters. A detailed computational model summarizing these physiological properties allowed to explore diferent functional confgurations of the parallel fber—stellate cell—Purkinje cell circuit. Simulations showed that, following parallel fber stimulation, Purkinje cells almost linearly increased their response with input frequency, but such an increase was inhibited by stellate cells, which leveled the Purkinje cell gain curve to its 4 Hz value. When reciprocal inhibitory connections between stellate cells were activated, the control of stellate cells over Purkinje cell discharge was maintained only at very high frequencies. These simulations thus predict a new role for stellate cells, which could endow the molecular layer with low-pass and band-pass fltering properties regulating Purkinje cell gain and, along with this, also burst delay and the burst-pause responses pattern.