Biology subjects

Houlgreave, M. S.

Publications and source records attributed to Houlgreave, M. S..

3 recordsLinked to original sources

bioRxiv2026

Sensorimotor mapping of volitional facial movements in Tourette Syndrome

BackgroundTourette Syndrome (TS) is a neurodevelopmental movement disorder involving involuntary motor and vocal tics believed to be characterised by disordered neural inhibition. Cortical representations have previously been manipulated by disruptions in the inhibitory neurotransmitter {gamma}-aminobutyric acid (GABA). However, while facial tics are the most reported motor tic, it is unclear if facial sensorimotor representations differ in TS. MethodsSixteen individuals with Tourette Syndrome (TS) or chronic tic disorder and twenty typically developing (TD) control participants underwent 3-Tesla functional magnetic resonance imaging (fMRI). Blood-oxygenation level-dependent (BOLD) responses were measured during a block-design task comprising cued facial movements of common facial tics (blinking, grimacing and jaw clenching). Activations in bilateral pre- and post-central cortices and supplementary motor areas (SMA) were examined. Conjunction analyses identified voxels commonly and uniquely activated across movements within each group. ResultsBoth groups showed significant activations in the bilateral sensorimotor cortices and SMA in response to blink, grimace and jaw clench movements, with no significant between-group differences. Between-group similarities were lowest for unique blink maps. Common voxel maps also revealed low between-group similarity, with reduced sensorimotor activation and no shared SMA activation across movements in the TS group. ConclusionVoluntary facial sensorimotor representations do not differ between groups. However, low similarities between group unique blink maps may reflect greater prevalence of blinking tics in TS. Additionally, reduced overlap in sensorimotor activation and absent common SMA engagement across cued movements in the TS group may indicate altered motor integration or action initiation.

neuroscience↗

bioRxiv2024

Uncovering the Neural Correlates of the Urge-to-Blink: A Study Utilising Subjective Urge Ratings and Paradigm Free Mapping

Neuroimaging plays a significant role in understanding the neurophysiology of Tourette syndrome (TS), in particular the main symptom, tics, and the urges associated with them. Premonitory urge is thought to be a negative reinforcer of tic expression in TS. Tic expression during neuroimaging is most often required as an overt marker of increased urge-to-tic, which can lead to considerable head movement, and thus data loss. This study aims to identify the brain regions involved in urge in healthy subjects using multi-echo functional MRI and a timing- free approach to localise the BOLD response associated with the urge-to-act without information of when these events occur. Blink suppression is an analogous behaviour that can be expressed overtly in the MRI scanner which gives rise to an urge like those described by individuals with TS. We examined the urge-to-blink in 20 healthy volunteers with an experimental paradigm including two conditions, "Okay to blink" and "Suppress blinking", to identify brain regions involved in blink suppression. Multi-echo functional MRI data was analysed using a novel approach to investigate the BOLD signal correlated with the build-up of the urge-to-blink that participants continuously reported using a rollerball device. In addition, we used the method of multi-echo paradigm free mapping (MESPFM) to identify these regions without prior specification of task timings. Subjective urge scores were correlated with activity in the right posterior and ventral-anterior insula as well as the mid-cingulate and occipital cortices. Furthermore, blink suppression was associated with activation in the dorsolateral prefrontal cortex, cerebellum, right dorsal-anterior insula, mid-cingulate cortex and thalamus. These findings illustrate that different insula subregions contribute to the urge-for-action and suppression networks. The MESPFM approach showed co-activation of the right insula and cingulate cortex. The MESPFM activation maps showed the highest overlap with activation associated with blink suppression, as identified using general linear model analysis, demonstrating that activity associated with suppression can be determined without prior knowledge of task timings.

neuroscience↗

bioRxiv2020

The Oscillatory Effects of Rhythmic Median Nerve Stimulation

Entrainment of brain oscillations can be achieved using rhythmic non-invasive brain stimulation, and stimulation of the motor cortex at a frequency associated with sensorimotor inhibition can impair motor responses. Despite the potential for therapeutic application, these techniques do not lend themselves to use outside of a clinical setting. Here, the aim was to investigate whether rhythmic median nerve stimulation (MNS) could be used to entrain oscillations related to sensorimotor inhibition. MEG data were recorded from 20 participants during 400 trials, where for each trial 10 pulses of MNS were delivered either rhythmically or arrhythmically at 12 or 20Hz. Our results demonstrate a frequency specific increase in relative amplitude in the contralateral somatosensory cortex during rhythmic but not arrhythmic stimulation. This was coupled with an increase in inter-trial phase coherence at the same frequency, suggesting that the oscillations synchronised with the pulses of MNS. While the results show that 20Hz rhythmic peripheral nerve stimulation can produce entrainment, the response to 12Hz stimulation was largely due to the presence of rhythmic sensory evoked potentials. Regardless, rhythmic MNS resulted in synchronous firing of neuronal populations within the contralateral somatosensory cortex meaning these neurons were occupied in processing of the afferent input. Therefore, MNS could prove therapeutically useful in disorders associated with hyperexcitability within the sensorimotor cortices.

neuroscience↗