Biology subjects

Jackson, G. M.

Publications and source records attributed to Jackson, G. M..

3 recordsLinked to original sources

bioRxiv2020

Examining the neural antecedents of tics in Tourette syndrome using electroencephalography

Tourette syndrome (TS) is a neurological disorder of childhood onset that is characterised by the occurrence of motor and vocal tics. TS is associated with cortical-striatal-thalamic-cortical circuit [CSTC] dysfunction and hyper-excitability of cortical limbic and motor regions that are thought to lead to the occurrence of tics. Importantly, individuals with TS often report that their tics are preceded by premonitory sensory/urge phenomena (PU) that are described as uncomfortable bodily sensations that precede the execution of a tic and are experienced as a strong urge for motor discharge. While tics are most often referred to as involuntary movements, it has been argued that tics should be viewed as voluntary movements that are executed in response to the presence of PU and bring temporary relief from the uncomfortable bodily sensations that are associated with PU. This issue remains unresolved but has very important implications for the design of clinical interventions for TS. To investigate this issue further, we conducted a study using electroencephalography (EEG). Specifically, we recorded movement-related EEG (mu and beta band oscillations) during (a) the immediate period leading up to the execution of voluntary movements by a group of individuals with TS and a group of matched healthy control participants, and (b) the immediate period leading up to the execution of a tic in a group of individuals with TS. We demonstrate that movement-related mu and beta band oscillations are not observed prior to tics in individuals with TS. We interpret this effect as reflecting the greater involvement of a network of brain areas, including the insular and cingulate cortices, basal ganglia nuclei, and the cerebellum, in the generation of tics in TS. We also show that beta-band desynchronization does occur when individuals with TS initiate voluntary movements, but, in contrast to healthy controls, desynchronization of mu-band oscillations is not observed during the execution of voluntary movements for individuals with TS. We interpret this finding as reflecting a dysfunction of physiological inhibition in TS, thereby contributing to an impaired ability to suppress neuronal populations that may compete with movement preparation processes.

neuroscience↗

bioRxiv2020

Entraining movement-related brain oscillations using rhythmic median nerve stimulation

Non-invasive brain stimulation techniques delivered to cortical motor areas have been shown previously to: modulate cortical motor excitability; entrain brain oscillations; and influence motor behavior; and have therefore attracted considerable interest as potential therapeutic approaches targeted for the treatment of movement disorders. However, these techniques are most often not suitable for treatment outside of the clinic, or for use with young children. We therefore investigated directly whether rhythmic pulses of median nerve stimulation (MNS) could be used to entrain brain oscillations linked to the suppression of movement. Using electroencephalography techniques together with concurrent MNS we demonstrate that 10 pulses of rhythmic MNS, delivered at 19Hz, is sufficient to entrain Beta-band brain oscillations within the contralateral sensorimotor cortex, whereas 10-pulse trains of arrhythmic MNS does not. This approach has potential in our view to be developed into a non-drug therapeutic device suitable for use outside of the research laboratory or the clinic with brain health conditions associated by excessive movements.

neuroscience↗

bioRxiv2020

The role of the cingulate cortex in the generation of motor tics and the experience of the premonitory urge-to-tic in Tourette syndrome

Tourette syndrome (TS) is a neurological disorder of childhood onset that is characterised by the occurrence of motor and vocal tics. TS is associated with cortical-striatal-thalamic-cortical circuit [CSTC] dysfunction and hyper-excitability of cortical limbic and motor regions that are thought to lead to the occurrence of tics. Individuals with TS often report that their tics are preceded by premonitory sensory/urge phenomena (PU) that are described as uncomfortable bodily sensations that precede the execution of a tic and are experienced as a strong urge for motor discharge. While the precise role played by PU in the occurrence of tics is largely unknown, they are nonetheless of considerable theoretical and clinical importance as they form a core component of many behavioural therapies used in the treatment of tic disorders. Recent evidence indicates that the cingulate cortex may play an important role in the generation of PU in TS, and in urges-for-action more generally. In the current study we utilised voxel-based morphometry (VBM) techniques, together with seed-to-voxel structural covariance network (SCN) mapping, to investigate the putative role played by the cingulate cortex in the generation of motor tics and the experience of PU in a relatively large group of young people with TS. Whole-brain VBM analysis revealed that TS was associated with clusters of significantly reduced grey matter volumes bilaterally within: the orbito-frontal cortex; the cerebellum; and the anterior and mid cingulate cortex. Similarly, analysis of SCNs associated with bilateral mid- and anterior-cingulate seed regions demonstrated that TS is associated with increased structural covariance primarily with the bilateral motor cerebellum; the inferior frontal cortex; and the posterior cingulate cortex.

neuroscience↗