Abstract
BackgroundPrevious one-dimensional network modeling of the cerebellar granular layer has been successfully linked with a range of cerebellar cortex oscillations observed in vivo. However, the recent discovery of gap junctions between Golgi cells (GoCs), which may cause oscillations by themselves, has raised the question of how gap-junction coupling affects GoC and granular-layer oscillations. To investigate this question, we developed a novel two-dimensional computational model of the GoC-granule cell (GC) circuit with and without gap junctions between GoCs.ResultsIsolated GoCs coupled by gap junctions had a strong tendency to generate spontaneous oscillations without affecting their mean firing frequencies in response to distributed mossy fiber input. Conversely, when GoCs were synaptically connected in the granular layer, gap junctions increased the power of the oscillations, but the oscillations were primarily driven by the synaptic feedback loop between GoCs and GCs, and the gap junctions did not change oscillation frequency or the mean firing rate of either GoCs or GCs.ConclusionOur modeling results suggest that gap junctions between GoCs increase the robustness of cerebellar cortex oscillations that are primarily driven by the feedback loop between GoCs and GCs. The robustness effect of gap junctions on synaptically driven oscillations observed in our model may be a general mechanism, also present in other regions of the brain.
Highlights
Previous one-dimensional network modeling of the cerebellar granular layer has been successfully linked with a range of cerebellar cortex oscillations observed in vivo
Local field potential (LFP) oscillations in the 5 to 30 Hz range have been recorded in the hemispheric regions of the cerebellar cortex [5,6,7,8], and previous one-dimensional network modeling of the cerebellar granular layer has been successfully linked with a range of in vivo oscillation data from the cerebellar cortex [9,10,11,12]
We previously showed that the granular layer oscillates when the parallel fiber (PF) input to Golgi cells (GoCs) is strong and it is activated by mossy fibers (MF) input; in the absence of PF input or of MF activation, GoC firing is desynchronized [9]
Summary
Previous one-dimensional network modeling of the cerebellar granular layer has been successfully linked with a range of cerebellar cortex oscillations observed in vivo. The recent discovery of gap junctions between Golgi cells (GoCs), which may cause oscillations by themselves, has raised the question of how gap-junction coupling affects GoC and granular-layer oscillations. The basic cerebellar cortex circuitry responsible for the generation of oscillations is driven by mossy fibers (MF) that excite both GCs [13,14] and Golgi cells (GoCs) [15,16,17]. The axons of the GCs form ascending fibers that bifurcate in both directions in the parallel fiber (PF) layer [18,19] These PFs excite GoCs along their way. MFs excite GoCs that inhibit GCs. The FB loop works through the MF-GC-PF-GoC-GC pathway.
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