Cerebellar Nuclear Neurons Use Time and Rate Coding to Transmit Purkinje Neuron Pauses.

Shyam Kumar Sudhakar,Benjamin Torben-Nielsen,Erik De Schutter,Kim T Blackwell

doi:10.1371/journal.pcbi.1004641

Abstract

Neurons of the cerebellar nuclei convey the final output of the cerebellum to their targets in various parts of the brain. Within the cerebellum their direct upstream connections originate from inhibitory Purkinje neurons. Purkinje neurons have a complex firing pattern of regular spikes interrupted by intermittent pauses of variable length. How can the cerebellar nucleus process this complex input pattern? In this modeling study, we investigate different forms of Purkinje neuron simple spike pause synchrony and its influence on candidate coding strategies in the cerebellar nuclei. That is, we investigate how different alignments of synchronous pauses in synthetic Purkinje neuron spike trains affect either time-locking or rate-changes in the downstream nuclei. We find that Purkinje neuron synchrony is mainly represented by changes in the firing rate of cerebellar nuclei neurons. Pause beginning synchronization produced a unique effect on nuclei neuron firing, while the effect of pause ending and pause overlapping synchronization could not be distinguished from each other. Pause beginning synchronization produced better time-locking of nuclear neurons for short length pauses. We also characterize the effect of pause length and spike jitter on the nuclear neuron firing. Additionally, we find that the rate of rebound responses in nuclear neurons after a synchronous pause is controlled by the firing rate of Purkinje neurons preceding it.

Highlights

Cerebellar nucleus (CN) neurons are crucial to the olivo-cerebellar circuit as they provide the sole output of the entire cerebellum [1,2]
In this study we analyze the importance of brief cessations in firing of the presynaptic neuron on the spiking of the postsynaptic neuron. We perform this analysis on the inhibitory synaptic connection between Purkinje neurons and nuclear neurons of the cerebellum
We employ a computational model of nuclear neurons and “synthetic” Purkinje neuron spike trains to study the effect of synchronous pauses on the spiking responses of nuclear neurons

Summary

Introduction

Cerebellar nucleus (CN) neurons are crucial to the olivo-cerebellar circuit as they provide the sole output of the entire cerebellum [1,2]. CN neuron’s firing patterns are of great importance for motor related tasks and representation of movement parameters [3]. Within the cerebellum, their direct upstream connections originate from the Purkinje neurons (PNs). The combination of intrinsic firing and synaptic input results in highly regular spikes with typical short pauses [12,13], where a pause is a short cease in firing. Given this elaborate firing pattern in PNs, how can the downstream CN neuron make sense out of this signal?

Methods

Results

Discussion

Conclusion