Spatiotemporal network coding of physiological mossy fiber inputs by the cerebellar granular layer.

Shyam Kumar Sudhakar,Daqing Guo,Erik De Schutter,Sungho Hong,Ivan Raikov,Claus Lang,Rodrigo Publio,Mario Negrello,Thomas Close,Kim T. Blackwell

doi:10.1371/journal.pcbi.1005754

Abstract

The granular layer, which mainly consists of granule and Golgi cells, is the first stage of the cerebellar cortex and processes spatiotemporal information transmitted by mossy fiber inputs with a wide variety of firing patterns. To study its dynamics at multiple time scales in response to inputs approximating real spatiotemporal patterns, we constructed a large-scale 3D network model of the granular layer. Patterned mossy fiber activity induces rhythmic Golgi cell activity that is synchronized by shared parallel fiber input and by gap junctions. This leads to long distance synchrony of Golgi cells along the transverse axis, powerfully regulating granule cell firing by imposing inhibition during a specific time window. The essential network mechanisms, including tunable Golgi cell oscillations, on-beam inhibition and NMDA receptors causing first winner keeps winning of granule cells, illustrate how fundamental properties of the granule layer operate in tandem to produce (1) well timed and spatially bound output, (2) a wide dynamic range of granule cell firing and (3) transient and coherent gating oscillations. These results substantially enrich our understanding of granule cell layer processing, which seems to promote spatial group selection of granule cell activity as a function of timing of mossy fiber input.

Highlights

The granular layer of the cerebellar cortex consists of populations of granule cells (GrCs), Golgi cells (GoCs), unipolar brush cells, and Lugaro cells [1,2,3]
The loop consists of AMPA and NMDA receptors of the GrCs activated by the mossy fiber input, AMPAergic receptors in the GoC population activated by the parallel fiber/ascending axon input, and GABAergic receptors in the GrCs activated by the GoCs
As observed in a previous 2D network model of the granular layer of cerebellar cortex [37], gap junctions between GoCs increased the synchrony of GoC and of GrC firing in case of low frequency diffuse mossy fiber input but had less effect when in addition a patch of mossy fibers was activated more strongly

Summary

Introduction

The granular layer of the cerebellar cortex consists of populations of granule cells (GrCs), Golgi cells (GoCs), unipolar brush cells, and Lugaro cells [1,2,3]. GoCs are inhibitory and are known as interneurons of the granular layer [1,5]. The granular layer of the cerebellar cortex receives its input from different parts of the brain primarily through mossy fibers [6]. The GrCs excite GoCs through parallel fibers [9,10,11] and ascending axons [12] and the GoCs in turn inhibit numerous GrCs through sagittal branching of their axons [5,13]. The GoCs are connected together by gap junctions [16,17,18] and have been reported to inhibit each other sparsely [19]

Methods

Results

Discussion

Conclusion