The specific origin of the simple and complex spikes in Purkinje neurons

Purkinje cells (PCs) are the main and only output neurons in the cerebellar cortex and have been implicated in motor coordination, learning and cognitive functions. There are two types of action potential output occurring in PCs: simple spikes (SSs) and complex spikes (CSs); both being generated in the axon (Stuart & Hausser, 1994). CSs are activated from a ¨ single excitatory input from a climbing fibre, originating at the inferior olive. They occur at a low frequency and produce a prolonged depolarization. Sensory stimuli, movement and feedback control are involved in originating CSs. SSs receive various inputs from mossy fibres and generate a brief, single-action, high-frequency, excitatory potential (Miall et al. 1998). Propioception, sensory and motor association area inputs are the main signals that trigger SSs. However, until now elucidation of the site of initiation of SSs and CSs has been nuclear.