Biology subjects

Houlgreave, M.

Publications and source records attributed to Houlgreave, M..

3 recordsLinked to original sources

bioRxiv2026

Exploring the beta burst dynamics of cued voluntary movements in Tourette Syndrome

Tourette Syndrome (TS) is a neurodevelopmental hyperkinetic disorder characterised by involuntary tics. These tics are thought to arise due to hyperexcitability of the motor cortex due to disinhibition within the cortico-striato-thalamo-cortical pathway. Given the involvement of motor circuits in this disorder, we explored whether there is a difference in the oscillatory dynamics of voluntary movements in people with tic disorders. We recorded optically pumped magnetometer magnetoencephalography during cued voluntary finger abductions in individuals with tic disorders and age- and sex-matched neurotypical controls. We analysed the data both using conventional time frequency analysis and using hidden Markov modelling to explore the difference in beta burst characteristics and dynamics. Whilst no differences were seen between groups during conventional analysis, we demonstrated an increase in beta burst duration during the post-movement beta rebound within the contralateral motor cortex in individuals with TS suggestive of increased inhibition following movement. We also show evidence of increased contralateral sensorimotor functional connectivity and reduced connectivity from and between frontal regions, as measured using coincident beta bursts. This is suggestive of disrupted functional connectivity within frontal control networks in individuals with TS.

neuroscience↗

bioRxiv2025

Disrupting action control with transcranial ultrasound neuromodulation: a step forward for Tourette syndrome

BackgroundWhile Tourette syndrome (TS) is characterised by the presence of tics, premonitory urges are involved in both triggering them and as a lever to control them. The right insular cortex is known to play a key role in these processes, yet its precise functional contribution remains unclear. Transcranial ultrasound stimulation (TUS) is currently one of the only non-invasive neuromodulation techniques capable of safely and precisely modulating the activity of deep brain structures such as the insula. ObjectiveThis study used TUS to causally investigate the respective roles of the anterior and posterior insula in urge and action control during a blink suppression task. MethodsTwenty healthy adults underwent three TUS sessions targeting the right anterior insula, posterior insula, and posterior ventricle (control site) in a within-subject, crossover design. Behavioural outcomes included blink counts and urge ratings. Additionally, voxel-based correlations were conducted to further estimate the role of each reached area with acoustic stimulation, allowing for a better mechanical understanding. ResultsTUS of the anterior insula induced a clear and acute increase in blink frequency without altering urge, reinforced by voxel-based analyses, confirming its role in voluntary action control. Posterior insula stimulation induced delayed increases in both blinks and urge, which are essentially explained by an involuntary stimulation of the right inferior frontal gyrus. Ventricular stimulation unexpectedly reduced blink frequency during the stimulation only, correlated with acoustic energy delivered within the posterior internal capsule. No significant side effects or temperature rises were observed. ConclusionsThese findings provide the first causal evidence that TUS can modulate the two main features of TS: premonitory urge and action control. Distinct effects across targets highlight the anterior insulas critical role in action control and suggest the internal capsule as a potential therapeutic target for TS.

neuroscience↗

bioRxiv2024

Investigating neurometabolite changes in response to median nerve stimulation

BackgroundRhythmic median nerve stimulation (MNS) at 10Hz has been shown to cause a substantial reduction in tic frequency in individuals with Tourette Syndrome. The mechanism of action is currently unknown, but is hypothesised to involve entrainment of oscillations within the sensorimotor cortex. ObjectiveWe used functional magnetic resonance spectroscopy (fMRS) to explore the dynamic effects of MNS on neurometabolite concentrations. MethodsHere, we investigated the effects of rhythmic and arrhythmic 10Hz MNS on glutamate (Glu) and GABA concentrations in the contralateral sensorimotor cortex in 15 healthy controls, using a blocked fMRS design. We used a Mescher-Garwood-semi-localised by adiabatic selective refocusing (MEGA-sLASER) sequence at 7T. ResultsOur results show no difference in the difference-from-baseline measures between the two stimulation conditions. Looking at the effect of MNS over both conditions there is a trend for an initial increase in Glu/tCr (total creatine) followed by a decrease over time, whereas GABA/tCr decreased during each stimulation block. ConclusionThese results suggest that despite entrainment of oscillations during rhythmic MNS, there are no significant differences in the tonic neuromodulatory effects of rhythmic and arrhythmic stimulation. The reduction in glutamate over the course of stimulation may reflect a decrease in glutamatergic firing due to adaptation. This may make it less likely that an involuntary movement is generated during continuous stimulation.

neuroscience↗