Cerebellar Purkinje neurons are arguably some of the most conspicuous neurons in the vertebrate central nervous system. They have characteristic planar fan-shaped dendrites which branch extensively and fill spaces almost completely with little overlap. This dendritic morphology is well suited to receiving a single or a few excitatory synaptic inputs from each of more than 100,000 parallel fibers which run orthogonally to Purkinje cell dendritic trees. In contrast, another type of excitatory input to a Purkinje neuron is provided by a single climbing fiber, which forms some hundreds to thousands of synapses with a Purkinje neuron. This striking contrast between the two types of synaptic inputs to a Purkinje neuron has attracted many neuroscientists. It is also to be noted that Purkinje neurons are the sole neurons sending outputs from the cerebellar cortex. In other words, all computational results within the cortex are transmitted by Purkinje cell axons, which inhibit neurons in the cerebellar or vestibular nucleus. Notably, Purkinje neurons show several forms of synaptic plasticity. Among them, long-term depression (LTD) at parallel fiber synapses has been regarded as a putatively essential mechanism for cerebellum-dependent learning. In this special issue on Purkinje neurons, you will find informative reviews and original papers on the development, characteristics and functions of Purkinje neurons, or related themes contributed by outstanding researchers.
Keywords: Climbing fiber; Dendrite arborization; Disease; Motor control; Purkinje neuron; Synapse elimination; Synapse formation; Synaptic plasticity.