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Title: The cerebellar cortex and motor learning
Author: Millar, Laurie
ISNI:       0000 0001 3398 9335
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2004
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Classical conditioning of the rabbit eyeblink/nictitating membrane response (EB/NMR) is dependent on the cerebellum and associated structures. Acquisition of conditioned responses (CRs) is prevented when normal function of either the anterior interpositus nucleus (AIP), lobule HVI of the cerebellar cortex or the inferior olive is functionally disrupted during conditioning. These three regions are connected to form the olivo-cortico-nuclear loop (OCN). So, disrupting normal processing at any one site within the OCN loop has functional consequences throughout the circuit, so the relative roles of HVI and the AIP cannot be dissociated. Some models suggest that HVI regulates the learned timing of conditioned responses, whereas others suggest HVI is where the critical association occurs and so is the principal site for learning-related plasticity. Here, three different approaches are used to understand the function of cortical HVI in conditioning. The first experimental study used electrophysiology to identify and characterise an EB/ NM microzone within the inferior region of HVI and this microzone was mapped in relation to patterns of Zebrin II expression revealed by immunocytochemistry. The studies presented in chapters 3 and 4 use temporary functional inactivation of HVI to investigate its role in extinction learning and consolidation. It was shown that normal function of HVI is critical for extinction learning and that the adaptive timing of CRs remains constant throughout both acquisition and extinction training. Cortical infusions of the GABAA receptor antagonist (SR 95531) intended to disrupt post-training consolidation processes impaired the acquisition of CRs 24 hours following the infusion but acquisition and post-training consolidation effects could not be dissociated. These studies provide evidence for the critical involvement of HVI. The findings are consistent with the suggestion that there is memory storage in the cerebellar cortex but essential plasticity at other levels is not ruled out.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available