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The origin of calcium signals associated with cerebellar learning

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Learning processes in the nervous system are produced by changes of the connections among neurons that form neuronal networks. To associate two inputs that normally produce two independent calcium signals, the concomitant occurrence of them can trigger a calcium signal that is larger than the summation of the two inputs and that is capable of changing one of the two inputs.

In cerebellar Purkinje neurons, a mechanism of this type allows learning of motor patterns underlying movement coordination. In the current issue of The Journal of Neuroscience, researchers of the LIPhy unravel the principal mechanisms underlying this supralinear calcium signal in Purkinje neurons. In this system, an important component of the calcium signal is mediated by a calcium channel activated by the first broad input, but the same signal is amplified locally when the second input is also activated. This channel operates only when the Purkinje neuron is not firing, suggesting that this transient state of the neuron is fundamental for learning of new information. This finding can potentially change our understanding of cerebellar learning that is perhaps more sophisticated than we have thought so far.

Figure legend. Purkinje neuron with two input indicated : 1. the climbing fibre ; 2. the parallel fibers. The concomitant activation of the two inputs (1+2) triggers a supralinear calcium signal by amplification of the calcium influx via T-type calcium channels.

Voir en ligne : The origin of physiological local mGluR1 supralinear Ca2+ signals in cerebellar Purkinje neurons. Ait Ouares K, Canepari M. J Neurosci 40 : 1795-1809, 2020.