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Synaptic plasticity in medial vestibular nucleus neurons: comparison with computational requirements of VOR adaptation

Menzies, J.R.W., Porrill, J., Dutia, M. and Dean, P. (2010) Synaptic plasticity in medial vestibular nucleus neurons: comparison with computational requirements of VOR adaptation. Plos One , 5 (10). Art no.e13182 . ISSN 1932-6203

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Abstract

Background: Vestibulo-ocular reflex (VOR) gain adaptation, a longstanding experimental model of cerebellar learning, utilizes sites of plasticity in both cerebellar cortex and brainstem. However, the mechanisms by which the activity of cortical Purkinje cells may guide synaptic plasticity in brainstem vestibular neurons are unclear. Theoretical analyses indicate that vestibular plasticity should depend upon the correlation between Purkinje cell and vestibular afferent inputs, so that, in gain-down learning for example, increased cortical activity should induce long-term depression (LTD) at vestibular synapses.

Methodology/Principal Findings: Here we expressed this correlational learning rule in its simplest form, as an anti-Hebbian, heterosynaptic spike-timing dependent plasticity interaction between excitatory (vestibular) and inhibitory (floccular) inputs converging on medial vestibular nucleus (MVN) neurons (input-spike-timing dependent plasticity, iSTDP). To test this rule, we stimulated vestibular afferents to evoke EPSCs in rat MVN neurons in vitro. Control EPSC recordings were followed by an induction protocol where membrane hyperpolarizing pulses, mimicking IPSPs evoked by flocculus inputs, were paired with single vestibular nerve stimuli. A robust LTD developed at vestibular synapses when the afferent EPSPs coincided with membrane hyperpolarisation, while EPSPs occurring before or after the simulated IPSPs induced no lasting change. Furthermore, the iSTDP rule also successfully predicted the effects of a complex protocol using EPSP trains designed to mimic classical conditioning.

Conclusions: These results, in strong support of theoretical predictions, suggest that the cerebellum alters the strength of vestibular synapses on MVN neurons through hetero-synaptic, anti-Hebbian iSTDP. Since the iSTDP rule does not depend on post-synaptic firing, it suggests a possible mechanism for VOR adaptation without compromising gaze-holding and VOR performance in vivo.

Item Type: Article
Copyright, Publisher and Additional Information: © 2010 Menzies et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Keywords: Long-Term Depression; Deep Cerebrellar Nuclei; D-aspartate RECEPTORS; MOSSY FIBER EPSCS; Vestibuloocular Reflex; Glutamate Receptors; Developmental Shift; Instructive Signals; NMDA Receptors; Nervous-System
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Department of Psychology (Sheffield)
Depositing User: Miss Anthea Tucker
Date Deposited: 29 Oct 2010 14:35
Last Modified: 16 Jun 2014 11:42
Published Version: http://dx.doi.org/10.1371/journal.pone.0013182
Status: Published
Publisher: Public Library Science
Refereed: Yes
Identification Number: 10.1371/journal.pone.0013182
URI: http://eprints.whiterose.ac.uk/id/eprint/42607

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