Part I: The Complex Spikes as One of the Cerebellar Secrets

The olivocerebellar tract has unique morphological, physiological, and developmental properties. Olivocerebellar axons are the source of multiple climbing fibers (CFs). The synapse between CFs and the Purkinje neuron is one of the most powerful excitatory in the central nervous system. Complex spikes are composed of an initial large amplitude spike followed by spikelets. The spatiotemporal patterns of complex/simple spikes complement the rate coding to enhance the accuracy of motor and cognitive processing, and to improve predictions related to internal models. Understanding the role of complex spikes is essential in clarifying how the cerebellar cortex contributes to learning, motor control, cognitive tasks, and the processing of emotions. This Cerebellar Classic is devoted to the pioneering work of Eccles, Llinás, and Sasaki on complex spikes using intracellular recordings from Purkinje neurons.