There is heterogeneity in parallel fiber-driven Purkinje cell firing even when fast synaptic transmission was not blocked. a–c, Top, Representative trace of cell-attached recordings, where 0 marks the time of five PF stimulations at 100 Hz. Bottom, Normalized spike frequency binned into 100 ms bins for (a) lobules IV/V, (b) lobule X, and (c) the flocculus. These recordings did not contain NBQX or picrotoxin, and therefore fast excitatory and inhibitory synaptic transmission were intact. (Lobules IV/V = 13 cells from 5 mice, lobule X = 9 cells from 4 mice, flocculus = 10 cells from 3 mice).