Katherine Dyke | University of Nottingham (original) (raw)

Papers by Katherine Dyke

bioRxiv (Cold Spring Harbor Laboratory), May 21, 2024

Developmental Medicine & Child Neurology, Feb 26, 2021

Experimental Brain Research, Oct 13, 2021

Tourette syndrome (TS) is a neurodevelopmental condition characterised by tics, which are stereot... more Tourette syndrome (TS) is a neurodevelopmental condition characterised by tics, which are stereotyped movements and/or vocalisations. Tics often cause difficulties in daily life and many with TS express a desire to reduce and/or gain control over them. No singular effective treatment exists for TS, and while pharmacological and behavioural interventions can be effective, the results are variable, and issues relating to access, availability and side effects can be barriers to treatment. Consequently, over the past decade, there has been increasing interest into the potential benefits of non-invasive brain stimulation (NIBS) approaches. This systematic review highlights work exploring NIBS as a potential treatment for TS. On balance, the results tentatively suggest that multiple sessions of stimulation applied over the supplementary motor area (SMA) may help to reduce tics. However, a number of methodological and theoretical issues limit the strength of this conclusion, with the most problematic being the lack of large-scale sham-controlled studies. In this review, methodological and theoretical issues are discussed, unanswered questions highlighted and suggestions for future work put forward.

Brain Stimulation, Nov 1, 2018

Cortex, May 1, 2020

Tourette syndrome (TS) is a neurological disorder of childhood onset that is characterised by the... more 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 corticalstriatal-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 the precise role played by PU in the occurrence of tics is largely unknown, they are nonetheless of considerable theoretical and clinical importance, not least because they form the core component in many behavioural therapies used in the treatment of tic disorders. Several lines of evidence indicate that the insular cortex may play a particularly important role in the generation of PU in TS and 'urges-for-action' more generally. In the current study we utilised voxel-based morphometry techniques together with 'seed-to-voxel' structural covariance network (SCN) mapping to investigate the putative role played by the right insular cortex in the generation of motor tics and the experience of PU in a relatively large group of young people TS. We demonstrate that clinical measures of motor tic severity and PU are uncorrelated with one another, that motor tic severity and PU scores are associated with separate regions of the insular cortex, and that the insula is associated with different structural covariance networks in individuals with TS compared to a matched group of typically developing individuals.

NeuroImage, May 1, 2017

Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networ... more Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networks are thought to underlie many brain and mental health disorders, and for this reason there is considerable interest in investigating how individual variability in localised concentrations of these molecules relate to brain disorders. Magnetic resonance spectroscopy (MRS) provides a reliable means of measuring, in vivo, concentrations of neurometabolites such as GABA, glutamate and glutamine that can be correlated with brain function and dysfunction. However, an issue of much debate is whether the GABA observed and measured using MRS represents the entire pool of GABA available for measurement (i.e., metabolic, intracellular, and extracellular) or is instead limited to only some portion of it. GABA function can also be investigated indirectly in humans through the use of non-invasive transcranial magnetic stimulation (TMS) techniques that can be used to measure cortical excitability and GABA-mediated physiological inhibition. To investigate this issue further we collected in a single session both types of measurement, i.e., TMS measures of cortical excitability and physiological inhibition and ultra-high-field (7 T) MRS measures of GABA, glutamate and glutamine, from the left sensorimotor cortex of the same group of right-handed individuals. We found that TMS and MRS measures were largely uncorrelated with one another, save for the plateau of the TMS IO curve that was negatively correlated with MRS-Glutamate (Glu) and intra-cortical facilitation (10ms ISI) that was positively associated with MRS-Glutamate concentration. These findings are consistent with the view that the GABA concentrations measured using the MRS largely represent pools of GABA that are linked to tonic rather than phasic inhibition and thus contribute to the inhibitory tone of a brain area rather than GABAergic synaptic transmission.

Developmental Medicine & Child Neurology, Apr 10, 2023

This commentary is on the original article by Batschelett et al. on pages 1321–1331 of this issue.

Transcranial direct current stimulation (tDCS) is a popular non-invasive brain stimulation techni... more Transcranial direct current stimulation (tDCS) is a popular non-invasive brain stimulation technique, which has the potential to modulate cortical excitability. The effects of tDCS are known to outlast the stimulation period, and in some cases, repeated applications have been found to produce long lasting clinically relevant effects. The primary aim of this thesis was to explore the reliability and therapeutic potential of this technique. In Chapters 3 and 4 transcranial magnetic stimulation (TMS) was used to measure tDCS effects. These experiments revealed substantial variability regarding the way in which healthy adults responded to stimulation. Notably, there were differences between participants regarding the direction and magnitude of change in cortical excitability. Furthermore, even when group level effects were found reliably, there was substantial intra-subject variability across repeated testing sessions. Subsequent experiments in Chapters 5 and 6, explored the biological and behavioural effects of tDCS in individuals with Gille de la Tourette's syndrome (GTS). GTS is a neurodevelopmental disorder characterised by motor and phonic tics which have been linked to hyper excitability within motor-cortical regions. Therefore, these experiments aimed to reduce cortical excitability of targeted regions in the hope that this would impact on tics. Disappointingly, no such effects were found immediately after a single session of tDCS (Chapter 5). Consequently, it was hypothesised that repeated applications may be necessary for significant reductions in tics to occur. This was investigated in Chapter 6 using an in-depth case study. The results were encouraging, in particular there was a substantial drop in tics following 10 days of tDCS at 1.5mA intensity. The stimulation was well tolerated and the treatment regimens were closely adhered to, despite tDCS being delivered in the participants own home with remote supervision. A weaker stimulation intensity was not as effective. The findings of Chapters 3-6 highlight that the optimal stimulation parameters may vary from person to person, and that exploration of individual data is critical in therapeutic contexts. The results also suggest that tDCS may be helpful as a treatment for GTS and furthermore highlight the feasibility of home use stimulation. Gabapentin 8.4 Limitations and suggestions for future research 8.5 Conclusions References Appendices Appendix i: Effects of tDCS on MEPs (Ch.3) Appendix ii: Individual variability & 2mA anodal tDCS (Ch. 3) Appendix iii: Effects of tDCS on raw IO curve slope (Ch. 3) Appendix iv: Sigmoidal fitting with IO curve data (Ch. 4) Appendix v: ICC analysis for Rush (Ch. 5) Appendix vi: Sigmoidal curve fitting (Ch. 5) Appendix vii: Further analysis with RUSH score (Ch. 5

Tourette syndrome (TS) and chronic tic disorder (CTD) are neurological disorders of childhood ons... more Tourette syndrome (TS) and chronic tic disorder (CTD) are neurological disorders of childhood onset characterised by the occurrence of tics; repetitive, purposeless, movements or vocalisations of short duration which can occur many times throughout a day. Currently, effective treatment for tic disorders is an area of considerable unmet clinical need. We aimed to evaluate the efficacy of a home-administered neuromodulation treatment for tics involving the delivery of rhythmic pulse trains of median nerve stimulation (MNS) delivered via a wearable ‘watch-like’ device worn at the wrist. We conducted a UK-wide parallel double-blind sham-controlled trial for the reduction of tics in individuals with tic disorder. The device was programmed to deliver rhythmic (10Hz) trains of low-intensity (1-19 mA) electrical stimulation to the median nerve for a pre-determined duration each day, and was intended to be used by each participant in their home once each day, 5 days each week, for a period o...

Oxford University Press eBooks, Apr 1, 2022

Brain, 2018

for a scientific commentary on this article. Current theories of motor control emphasize how the ... more for a scientific commentary on this article. Current theories of motor control emphasize how the brain may use internal models of the body to ensure accurate planning and control of movements. One such internal model-a forward model-is thought to generate an estimate of the next motor state and/or the sensory consequences of an upcoming movement, thereby allowing movement errors to be monitored. In addition, forward models may provide a means by which to determine a sense of agency, i.e. the (conscious) sense of authorship and control over our actions. Tourette syndrome is a developmental neurological condition characterized by the occurrence of motor and phonic tics. The involuntary (or voluntary) nature of tics has been the subject of considerable debate, and it was recently argued that the presence of tics in Tourette syndrome could result in a blurring of any subjective boundary between voluntary and involuntary movements. In particular, it was proposed that the level of sensorimotor noise that accompanies tics may be particularly high in Tourette syndrome, and this may contribute to less efficient forward models used to determine agency. We investigated whether the internal monitoring of movements is impaired in individuals with Tourette syndrome, relative to a matched group of typically developing individuals, using a task that involved executing double-step aiming movements using a hand-held robot manipulandum. Participants were required on each trial to execute two movements in turn, each directed to a remembered target location without visual feedback. Importantly, we assumed that to perform accurately on the second (return) movement it would be necessary to update any forward model to take into account errors made during the first (outward) movement. Here we demonstrate that while the Tourette syndrome group were equally accurate, and no more variable, than the matched control group in executing aiming movements to the first (outward) target location, they were significantly less accurate, and exhibited greater movement variability, than controls when executing the second (return) movement. Furthermore, we show that for the return movement only, movement accuracy and movement variability were significantly predicted by the Tourette syndrome group's clinical severity scores. We interpret these findings as consistent with the view that individuals with Tourette syndrome may experience a reduction in the precision of the forward model estimates thought necessary for the accurate planning and control of movements.

Clinical Neurophysiology, 2017

medRxiv (Cold Spring Harbor Laboratory), Mar 7, 2023

A double-blind, sham-controlled, trial of home-administered rhythmic 10Hz median nerve stimulatio... more A double-blind, sham-controlled, trial of home-administered rhythmic 10Hz median nerve stimulation for the reduction of tics, and suppression of the urge-to-tic, in individuals with Tourette syndrome and chronic tic disorder

International Review of Movement Disorders

Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are c... more Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are characterised by the occurrence of tics; repetitive, purposeless, movements or vocalisations of short duration which can occur many times throughout a day. One of the defining characteristics of tics, and one that distinguishes them from other kinds of abnormal movement, is that they can often be suppressed for a period of time. However, tic suppression is invariably associated with increasing levels of discomfort which is most often experienced as a strong urge-to-tic (PU). Importantly, PU are uncomfortable sensory phenomena, often described as feelings of discomfort or pressure which can be temporally reduced after tic execution. Individuals who experience PU often report that: these experiences are more bothersome than their tics; that expressing their tics give them relief from, and temporarily abolishes, their PU; and that they would not exhibit tics if they did not experience PU. Fo...

International Review of Movement Disorders

Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are c... more Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are characterised by the occurrence of tics; repetitive, purposeless, movements or vocalisations of short duration which can occur many times throughout a day. One of the defining characteristics of tics, and one that distinguishes them from other kinds of abnormal movement, is that they can often be suppressed for a period of time. However, tic suppression is invariably associated with increasing levels of discomfort which is most often experienced as a strong urge-to-tic (PU). Importantly, PU are uncomfortable sensory phenomena, often described as feelings of discomfort or pressure which can be temporally reduced after tic execution. Individuals who experience PU often report that: these experiences are more bothersome than their tics; that expressing their tics give them relief from, and temporarily abolishes, their PU; and that they would not exhibit tics if they did not experience PU. Fo...

Tourette syndrome is a neurodevelopmental condition which affects approximately 0.6% to 1% of 5to... more Tourette syndrome is a neurodevelopmental condition which affects approximately 0.6% to 1% of 5to 18-yearolds. The condition is characterized by the occurrence of tics, which are stereotyped movements and/or vocalizations. Having Tourette syndrome can have a substantial negative impact on an individual’s quality of life; consequently, many people with the condition seek treatment to help manage their tics. Pharmacological and behavioural interventions can be effective. However, individual outcomes are highly varied and issues relating to access, availability, and side effects can be barriers to treatment. There has been increased interest in the therapeutic application of non-invasive brain stimulation approaches, including interventions using repetitive transcranial magnetic stimulation (rTMS). rTMS has been shown to modulate neural plasticity for a period of time extending beyond stimulation. These after-effects have been hypothesized to be reliant on synaptic events similar to th...

NeuroImage, May 8, 2017

Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networ... more Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networks are thought to underlie many brain and mental health disorders, and for this reason there is considerable interest in investigating how individual variability in localised concentrations of these molecules relate to brain disorders. Magnetic resonance spectroscopy (MRS) provides a reliable means of measuring, in vivo, concentrations of neurometabolites such as GABA, glutamate and glutamine that can be correlated with brain function and dysfunction. However, an issue of much debate is whether the GABA observed and measured using MRS represents the entire pool of GABA available for measurement (i.e., metabolic, intracellular, and extracellular) or is instead limited to only some portion of it. GABA function can also be investigated indirectly in humans through the use of non-invasive transcranial magnetic stimulation (TMS) techniques that can be used to measure cortical excitability and...

bioRxiv (Cold Spring Harbor Laboratory), May 21, 2024

Developmental Medicine & Child Neurology, Feb 26, 2021

Experimental Brain Research, Oct 13, 2021

Tourette syndrome (TS) is a neurodevelopmental condition characterised by tics, which are stereot... more Tourette syndrome (TS) is a neurodevelopmental condition characterised by tics, which are stereotyped movements and/or vocalisations. Tics often cause difficulties in daily life and many with TS express a desire to reduce and/or gain control over them. No singular effective treatment exists for TS, and while pharmacological and behavioural interventions can be effective, the results are variable, and issues relating to access, availability and side effects can be barriers to treatment. Consequently, over the past decade, there has been increasing interest into the potential benefits of non-invasive brain stimulation (NIBS) approaches. This systematic review highlights work exploring NIBS as a potential treatment for TS. On balance, the results tentatively suggest that multiple sessions of stimulation applied over the supplementary motor area (SMA) may help to reduce tics. However, a number of methodological and theoretical issues limit the strength of this conclusion, with the most problematic being the lack of large-scale sham-controlled studies. In this review, methodological and theoretical issues are discussed, unanswered questions highlighted and suggestions for future work put forward.

Brain Stimulation, Nov 1, 2018

Cortex, May 1, 2020

Tourette syndrome (TS) is a neurological disorder of childhood onset that is characterised by the... more 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 corticalstriatal-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 the precise role played by PU in the occurrence of tics is largely unknown, they are nonetheless of considerable theoretical and clinical importance, not least because they form the core component in many behavioural therapies used in the treatment of tic disorders. Several lines of evidence indicate that the insular cortex may play a particularly important role in the generation of PU in TS and 'urges-for-action' more generally. In the current study we utilised voxel-based morphometry techniques together with 'seed-to-voxel' structural covariance network (SCN) mapping to investigate the putative role played by the right insular cortex in the generation of motor tics and the experience of PU in a relatively large group of young people TS. We demonstrate that clinical measures of motor tic severity and PU are uncorrelated with one another, that motor tic severity and PU scores are associated with separate regions of the insular cortex, and that the insula is associated with different structural covariance networks in individuals with TS compared to a matched group of typically developing individuals.

NeuroImage, May 1, 2017

Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networ... more Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networks are thought to underlie many brain and mental health disorders, and for this reason there is considerable interest in investigating how individual variability in localised concentrations of these molecules relate to brain disorders. Magnetic resonance spectroscopy (MRS) provides a reliable means of measuring, in vivo, concentrations of neurometabolites such as GABA, glutamate and glutamine that can be correlated with brain function and dysfunction. However, an issue of much debate is whether the GABA observed and measured using MRS represents the entire pool of GABA available for measurement (i.e., metabolic, intracellular, and extracellular) or is instead limited to only some portion of it. GABA function can also be investigated indirectly in humans through the use of non-invasive transcranial magnetic stimulation (TMS) techniques that can be used to measure cortical excitability and GABA-mediated physiological inhibition. To investigate this issue further we collected in a single session both types of measurement, i.e., TMS measures of cortical excitability and physiological inhibition and ultra-high-field (7 T) MRS measures of GABA, glutamate and glutamine, from the left sensorimotor cortex of the same group of right-handed individuals. We found that TMS and MRS measures were largely uncorrelated with one another, save for the plateau of the TMS IO curve that was negatively correlated with MRS-Glutamate (Glu) and intra-cortical facilitation (10ms ISI) that was positively associated with MRS-Glutamate concentration. These findings are consistent with the view that the GABA concentrations measured using the MRS largely represent pools of GABA that are linked to tonic rather than phasic inhibition and thus contribute to the inhibitory tone of a brain area rather than GABAergic synaptic transmission.

Developmental Medicine & Child Neurology, Apr 10, 2023

This commentary is on the original article by Batschelett et al. on pages 1321–1331 of this issue.

Transcranial direct current stimulation (tDCS) is a popular non-invasive brain stimulation techni... more Transcranial direct current stimulation (tDCS) is a popular non-invasive brain stimulation technique, which has the potential to modulate cortical excitability. The effects of tDCS are known to outlast the stimulation period, and in some cases, repeated applications have been found to produce long lasting clinically relevant effects. The primary aim of this thesis was to explore the reliability and therapeutic potential of this technique. In Chapters 3 and 4 transcranial magnetic stimulation (TMS) was used to measure tDCS effects. These experiments revealed substantial variability regarding the way in which healthy adults responded to stimulation. Notably, there were differences between participants regarding the direction and magnitude of change in cortical excitability. Furthermore, even when group level effects were found reliably, there was substantial intra-subject variability across repeated testing sessions. Subsequent experiments in Chapters 5 and 6, explored the biological and behavioural effects of tDCS in individuals with Gille de la Tourette's syndrome (GTS). GTS is a neurodevelopmental disorder characterised by motor and phonic tics which have been linked to hyper excitability within motor-cortical regions. Therefore, these experiments aimed to reduce cortical excitability of targeted regions in the hope that this would impact on tics. Disappointingly, no such effects were found immediately after a single session of tDCS (Chapter 5). Consequently, it was hypothesised that repeated applications may be necessary for significant reductions in tics to occur. This was investigated in Chapter 6 using an in-depth case study. The results were encouraging, in particular there was a substantial drop in tics following 10 days of tDCS at 1.5mA intensity. The stimulation was well tolerated and the treatment regimens were closely adhered to, despite tDCS being delivered in the participants own home with remote supervision. A weaker stimulation intensity was not as effective. The findings of Chapters 3-6 highlight that the optimal stimulation parameters may vary from person to person, and that exploration of individual data is critical in therapeutic contexts. The results also suggest that tDCS may be helpful as a treatment for GTS and furthermore highlight the feasibility of home use stimulation. Gabapentin 8.4 Limitations and suggestions for future research 8.5 Conclusions References Appendices Appendix i: Effects of tDCS on MEPs (Ch.3) Appendix ii: Individual variability & 2mA anodal tDCS (Ch. 3) Appendix iii: Effects of tDCS on raw IO curve slope (Ch. 3) Appendix iv: Sigmoidal fitting with IO curve data (Ch. 4) Appendix v: ICC analysis for Rush (Ch. 5) Appendix vi: Sigmoidal curve fitting (Ch. 5) Appendix vii: Further analysis with RUSH score (Ch. 5

Tourette syndrome (TS) and chronic tic disorder (CTD) are neurological disorders of childhood ons... more Tourette syndrome (TS) and chronic tic disorder (CTD) are neurological disorders of childhood onset characterised by the occurrence of tics; repetitive, purposeless, movements or vocalisations of short duration which can occur many times throughout a day. Currently, effective treatment for tic disorders is an area of considerable unmet clinical need. We aimed to evaluate the efficacy of a home-administered neuromodulation treatment for tics involving the delivery of rhythmic pulse trains of median nerve stimulation (MNS) delivered via a wearable ‘watch-like’ device worn at the wrist. We conducted a UK-wide parallel double-blind sham-controlled trial for the reduction of tics in individuals with tic disorder. The device was programmed to deliver rhythmic (10Hz) trains of low-intensity (1-19 mA) electrical stimulation to the median nerve for a pre-determined duration each day, and was intended to be used by each participant in their home once each day, 5 days each week, for a period o...

Oxford University Press eBooks, Apr 1, 2022

Brain, 2018

for a scientific commentary on this article. Current theories of motor control emphasize how the ... more for a scientific commentary on this article. Current theories of motor control emphasize how the brain may use internal models of the body to ensure accurate planning and control of movements. One such internal model-a forward model-is thought to generate an estimate of the next motor state and/or the sensory consequences of an upcoming movement, thereby allowing movement errors to be monitored. In addition, forward models may provide a means by which to determine a sense of agency, i.e. the (conscious) sense of authorship and control over our actions. Tourette syndrome is a developmental neurological condition characterized by the occurrence of motor and phonic tics. The involuntary (or voluntary) nature of tics has been the subject of considerable debate, and it was recently argued that the presence of tics in Tourette syndrome could result in a blurring of any subjective boundary between voluntary and involuntary movements. In particular, it was proposed that the level of sensorimotor noise that accompanies tics may be particularly high in Tourette syndrome, and this may contribute to less efficient forward models used to determine agency. We investigated whether the internal monitoring of movements is impaired in individuals with Tourette syndrome, relative to a matched group of typically developing individuals, using a task that involved executing double-step aiming movements using a hand-held robot manipulandum. Participants were required on each trial to execute two movements in turn, each directed to a remembered target location without visual feedback. Importantly, we assumed that to perform accurately on the second (return) movement it would be necessary to update any forward model to take into account errors made during the first (outward) movement. Here we demonstrate that while the Tourette syndrome group were equally accurate, and no more variable, than the matched control group in executing aiming movements to the first (outward) target location, they were significantly less accurate, and exhibited greater movement variability, than controls when executing the second (return) movement. Furthermore, we show that for the return movement only, movement accuracy and movement variability were significantly predicted by the Tourette syndrome group's clinical severity scores. We interpret these findings as consistent with the view that individuals with Tourette syndrome may experience a reduction in the precision of the forward model estimates thought necessary for the accurate planning and control of movements.

Clinical Neurophysiology, 2017

medRxiv (Cold Spring Harbor Laboratory), Mar 7, 2023

A double-blind, sham-controlled, trial of home-administered rhythmic 10Hz median nerve stimulatio... more A double-blind, sham-controlled, trial of home-administered rhythmic 10Hz median nerve stimulation for the reduction of tics, and suppression of the urge-to-tic, in individuals with Tourette syndrome and chronic tic disorder

International Review of Movement Disorders

Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are c... more Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are characterised by the occurrence of tics; repetitive, purposeless, movements or vocalisations of short duration which can occur many times throughout a day. One of the defining characteristics of tics, and one that distinguishes them from other kinds of abnormal movement, is that they can often be suppressed for a period of time. However, tic suppression is invariably associated with increasing levels of discomfort which is most often experienced as a strong urge-to-tic (PU). Importantly, PU are uncomfortable sensory phenomena, often described as feelings of discomfort or pressure which can be temporally reduced after tic execution. Individuals who experience PU often report that: these experiences are more bothersome than their tics; that expressing their tics give them relief from, and temporarily abolishes, their PU; and that they would not exhibit tics if they did not experience PU. Fo...

International Review of Movement Disorders

Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are c... more Tourette syndrome (TS) and chronic tic disorder (CTD) are neurodevelopmental disorders that are characterised by the occurrence of tics; repetitive, purposeless, movements or vocalisations of short duration which can occur many times throughout a day. One of the defining characteristics of tics, and one that distinguishes them from other kinds of abnormal movement, is that they can often be suppressed for a period of time. However, tic suppression is invariably associated with increasing levels of discomfort which is most often experienced as a strong urge-to-tic (PU). Importantly, PU are uncomfortable sensory phenomena, often described as feelings of discomfort or pressure which can be temporally reduced after tic execution. Individuals who experience PU often report that: these experiences are more bothersome than their tics; that expressing their tics give them relief from, and temporarily abolishes, their PU; and that they would not exhibit tics if they did not experience PU. Fo...

Tourette syndrome is a neurodevelopmental condition which affects approximately 0.6% to 1% of 5to... more Tourette syndrome is a neurodevelopmental condition which affects approximately 0.6% to 1% of 5to 18-yearolds. The condition is characterized by the occurrence of tics, which are stereotyped movements and/or vocalizations. Having Tourette syndrome can have a substantial negative impact on an individual’s quality of life; consequently, many people with the condition seek treatment to help manage their tics. Pharmacological and behavioural interventions can be effective. However, individual outcomes are highly varied and issues relating to access, availability, and side effects can be barriers to treatment. There has been increased interest in the therapeutic application of non-invasive brain stimulation approaches, including interventions using repetitive transcranial magnetic stimulation (rTMS). rTMS has been shown to modulate neural plasticity for a period of time extending beyond stimulation. These after-effects have been hypothesized to be reliant on synaptic events similar to th...

NeuroImage, May 8, 2017

Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networ... more Imbalances in glutamatergic (excitatory) and GABA (inhibitory) signalling within key brain networks are thought to underlie many brain and mental health disorders, and for this reason there is considerable interest in investigating how individual variability in localised concentrations of these molecules relate to brain disorders. Magnetic resonance spectroscopy (MRS) provides a reliable means of measuring, in vivo, concentrations of neurometabolites such as GABA, glutamate and glutamine that can be correlated with brain function and dysfunction. However, an issue of much debate is whether the GABA observed and measured using MRS represents the entire pool of GABA available for measurement (i.e., metabolic, intracellular, and extracellular) or is instead limited to only some portion of it. GABA function can also be investigated indirectly in humans through the use of non-invasive transcranial magnetic stimulation (TMS) techniques that can be used to measure cortical excitability and...