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A Critical Window? Longitudinal Changes in Plasticity in Motor Cortex following Ischaemic Stroke

Austin, Duncan; (2020) A Critical Window? Longitudinal Changes in Plasticity in Motor Cortex following Ischaemic Stroke. Doctoral thesis (Ph.D), UCL (University London College). Green open access

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Abstract

While spontaneous recovery occurs in most patients following stroke, it is often incomplete. Recovery seems to be mostly confined to the first 6 months. Data from animal models suggest there is a critical period of enhanced plasticity similar to that seen in early development. Evidence for such a critical period has not yet been established in humans. Repetitive transcranial magnetic stimulation is a suitable tool for measuring changes in plasticity in human motor cortex. However, its long-term test-retest reliability has not been widely studied. Experiment 1 19 younger (average 29.9 years) and 20 older (average 65.9 years) subjects had repeat sessions of spaced cTBS to motor cortex 6 months apart. Change in average MEPs over 30 minutes post spaced cTBS showed fair intraclass correlation across 6 months in young (0.458 CI [-0.406, 0.791]) and older (0.572 [95%CI -0.08, 0.83]) subjects. This is broadly equivalent to other forms of plasticity-modulating non-invasive brain stimulation. Experiment 2 29 subjects (average 68.2 years) had repeat spaced cTBS to contralesional motor cortex at 2, 4, 6 and 26 weeks following ischaemic stroke. There was a significant decrease in LTDlike plasticity across sessions (p<0.01). There was no change in resting motor threshold in either hemisphere and no change in intracortical excitability. Small vessel disease measured on MRI did not influence response to spaced cTBS. Experiment 3 To complement the expansion in clinical research examining the benefits of fluoxetine in enhancing post-stroke plasticity, 31 healthy volunteers (average age 26.3 years) received fluoxetine 20mg or placebo prior to undergoing spaced cTBS in a double-blind randomised cross-over trial. There was no effect of fluoxetine on response to cTBS (p=0.472). Conclusions There is a decrease in LTD-like plasticity in the 6 months following a stroke in humans. 20mg of fluoxetine had no effect on LTD-like plasticity in healthy subjects.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: A Critical Window? Longitudinal Changes in Plasticity in Motor Cortex following Ischaemic Stroke
Event: UCL (University London College)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
URI: https://discovery.ucl.ac.uk/id/eprint/10094634
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