Investigating brain activity prior to tics and modulating this activity with peripheral nerve stimulation to suppress tics in Tourette syndrome

Morera Màiquez, Bàrbara (2021) Investigating brain activity prior to tics and modulating this activity with peripheral nerve stimulation to suppress tics in Tourette syndrome. PhD thesis, University of Nottingham.

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Abstract

Tourette syndrome (TS) is a neurological disorder characterized by motor and vocal tics. It is associated with a dysfunction in the cortical-striatal-thalamic-cortical (CSTC) circuit that leads to an overexcited motor cortex resulting in the execution of the motor or vocal action (tics). Most individuals report having uncomfortable sensations or premonitory urges (PU) preceding some of their tics, and many individuals report that their tics result from these sensations. Tic suppression is associated with an inhibited motor cortex and it is present during voluntary movements in order to perform the desired motor action.

The first aim of this thesis was to explore the brain activity preceding tics and brain activity preceding voluntary movement. To investigate this, I used electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to explore the brain activity preceding tics, and I used EEG to examine brain activity preceding voluntary movements in both healthy subjects and subjects with TS. Time-frequency analyses showed no consistent pattern of cortical activity preceding tics, although individual tics were characterized by the presence of an increased excitability in the sensorimotor cortex (SMC) before their execution; and BOLD activity showed activation in motor and sensory brain areas preceding tics, previously reported in other studies. Time-frequency analyses showed a reduced excitability in the SMC before voluntary movements in subjects with TS.

The second aim was to investigate the use of a non-invasive brain stimulation technique to modulate this cortical excitability. I used median nerve stimulation (MNS) while recording EEG to explore whether rhythmic MNS entrains brain oscillations in the SMC, then I used rhythmic MNS during a motor task to explore its effects on voluntary movement, finally I used rhythmic MNS on TS to explore its effects on tics. Time-frequency analyses and inter-trial coherence showed clear evidence that rhythmic MNS entrains brain oscillations in the sensorimotor cortex; response times in a computer motor task showed a reduction of speed in motor response during rhythmic MNS; video recordings showed a decrease in the number of tics during MNS.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Jackson, Stephen
Jackson, Georgina
Keywords: Tourette syndrome, TS, brain activity, electroencephalography, functional magnetic resonance imaging
Subjects: R Medicine > RC Internal medicine > RC 321 Neuroscience. Biological psychiatry. Neuropsychiatry
Faculties/Schools: UK Campuses > Faculty of Science > School of Psychology
Item ID: 64431
Depositing User: Morera, Barbara
Date Deposited: 04 Aug 2021 04:40
Last Modified: 04 Aug 2021 04:40
URI: http://eprints.nottingham.ac.uk/id/eprint/64431

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