Climbing Fibre Actions of Purkinje Cells — Plateau Potentials and Long-Lasting Depression of Parallel Fibre Responses
Understanding of the information processing occurring in the cerebellar cortex requires knowledge about the properties and specific functions of the two major kinds of afferents received by the Purkinje cells, the parallel fibres and the climbing fibres. The synapses between these two kinds of afferents and the Purkinje cells are both excitatory but have otherwise an entirely different organization. Each Purkinje cell receives about 100,000 parallel fibres which make synapses on the distal dendrites, but only one climbing fibre which makes an extraordinarily.powerful synaptic contact on more proximal dendrites. Activity in parallel fibres is, at least partly, responsible for the background activity of Purkinje cells which is usually between 20 and 100 Hz. A climbing fibre impulse causes a discharge of the Purkinje cell, which extracellularly is recorded as a “complex spike” from the soma. The complex spike consists of an initial action potential followed by one or a few abortive spikes. Although some of the abortive spikes may be conducted down the Purkinje cell axon (Ito and Simpson, 1971) the overall contribution of climbing fibres to the output activity of Purkinje cells must be small because of the low discharge rate of climbing fibres, usually 1–2 Hz.
KeywordsPurkinje Cell Parallel Fibre Climbing Fibre Plateau Potential Complex Spike
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