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Title: The functional relevance of cortico-cortical interactions in the human motor system
Author: Strens, Lucy Henrietta Alban
ISNI:       0000 0001 3488 3081
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2003
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By recording surface electroencephalographic (EEG) data from human subjects, it is possible to calculate measures of functional connectivity and to correlate these with behavioural changes induced with repetitive transcranial magnetic stimulation (rTMS). RTMS is a tool that can be used to cause temporary disruption to an area of cortex so that the effects of such "transient brain lesions" can be studied. This thesis investigates cortical plasticity in humans and, in particular, the functional relevance of cortico-cortical coherence in the motor system. Specifically, this work explores the effects of high (5Hz) and low (1Hz) frequency rTMS to the motor cortex and supplementary motor area (SMA). It investigates the relevance of such changes in connectivity to motor function using simple behavioural tasks such as finger tapping, reaction times and bimanual coordination. In addition, the cortico-cortical coherence recorded from stroke patients is compared with that from healthy subjects in an attempt to correlate coherence with recovery from stroke. This work demonstrates that rTMS to motor areas of the healthy human brain causes effects that outlast the duration of the train of stimulation. More specifically, rTMS to motor areas causes changes in cortico-cortical coherence, associated changes in motor behaviour and differential effects dependent on stimulation parameters. Disruption to one motor cortex with rTMS may be compensated for functionally by the opposite motor cortex in healthy humans. Lastly, changes in cortico-cortical connectivity after stroke were shown to relate to functional recovery. These results led to several conclusions. Firstly, rTMS can acutely disrupt cortical function at a behavioural level. Secondly, the effects of rTMS are partly mediated by changes in cortico-cortical coupling. Thirdly, the effects of rTMS are limited by acute plasticity at a cortical level. Fourthly, chronic plasticity in stroke is partly mediated by changes in cortico-cortical coupling.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available