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Models

Cerebellar Network Model

Network

A network model of the granular layer of cerebellar cortex (Maex and De Schutter)

The steady-state activity of a large-scale model circuit of the granular layer of the rat cerebellum was computed during continuous random mossy fiber input. Within less than 100 milliseconds after the start of mossy fiber activity, the populations of Golgi and granule cells became entrained in a single synchronous oscillation, the basic frequency of which ranged from 10 to 40 Hz depending on the rate of mossy fiber activity. The long parallel fibers ensured, through AMPA-mediated synapses, a coherent and equally strong excitation of Golgi cells, while each Golgi cell synchronized all granule cells within its axonal radius through transient activation of their GABAA receptor synapses. Individual granule cells often remained silent during a few successive oscillation periods so that their average firing rates, which were quite variable, reflected the average activities of their individual sets of mossy fiber afferents.

The network could be desynchronized respectively by very low model mossy fiber activity, by a dominant excitation of model Golgi cells by mossy fibers instead of parallel fibers, and by an almost complete absence of synaptically induced ipscs in model granule cells at the expense of a tonic activation of their extrasynaptic GABAA channels. Nevertheless, the synchronous rhythmic firing pattern was robust over a broad range of biologically realistic parameter values and to parameter randomization.

We propose that Golgi cells not only control the strength of parallel fiber activity but also the timing of the individual spikes. These spikes can become synchronized over large distances along the parallel fiber axis.

GENESIS2.1 scripts for this 1997 network model of the granular layer of cerebellar cortex as described in:
Maex, R. and De Schutter, E.: Synchronization of Golgi and granule cell firing in a detailed network model of the cerebellar granular layer. Journal of Neurophysiology 80: 2521-2537 (1998).