Functional mapping of facial movements in Tourette Syndrome

361 

Abstract Submission 

Caitlin Smith¹, Mairi Houlgreave¹, Michael Asghar², Susan Francis², Stephen Jackson¹

¹School of Psychology, University of Nottingham, Nottingham, England, ²Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, England

Caitlin Smith  
School of Psychology, University of Nottingham
Nottingham, England

Mairi Houlgreave  
School of Psychology, University of Nottingham
Nottingham, England

Michael Asghar  
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, England

Susan Francis  
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, England

Stephen Jackson  
School of Psychology, University of Nottingham
Nottingham, England

Key mechanisms implicated in the mediation of cortical activity and cortical representations are surround inhibition and the inhibitory neurotransmitter ƴ-aminobutyric acid (GABA). For instance, animal research has shown GABA antagonist injected into the motor cortex results in the fusion of motor representations between adjacent muscles and weakens sensory map plasticity and receptive field tuning (Jacobs et al., 1991). Evidence from Focal Hand Dystonia, a movement disorder characterised by involuntary muscle contractions in the hands and arms, has supported this link with evidence of impaired sensorimotor GABAergic inhibition (Levy et al., 2002) and abnormal and disorganised cortical mapping of the hand and digits (Meunier et al., 2001). Similarly, Tourette Syndrome (TS) is a movement disorder thought to be characterised by altered inhibition (Jackson et al., 2015). TS is a neurodevelopmental, hyperkinetic movement disorder involving involuntary motor and vocal tics. However, it is unclear if functional mapping of body parts commonly involved in tics are affected in TS, as this has not yet been investigated.

This study aimed to use task-fMRI to investigate the functional representations of different facial movements, a region commonly affected by tics in TS, in the motor and sensory cortices of those with TS and in healthy controls (HC).

Task-fMRI acquisition: 3T fMRI data were acquired using a 32-channel head coil (Philips, Ingenia) in 19 participants with TS or chronic tic disorder (8F, mean age: 34.7, SD: 11.2) and 13 HC participants (6F, mean age: 27.3, SD: 5.2). BOLD fMRI parameters included single-shot 2D T2*-weighted GE-EPI sequence (2.5 mm thickness, 48 slices, MB = 4, TR/TE = 1000/30 ms).
Three fMRI task blocks were acquired with participants visually instructed to perform a facial movement at 1Hz (8s ON, 24s OFF; 8 cycles). Each task block consisted of a different facial movement; blinking, grimacing, and jaw clenching. These movements are very common tics experienced by those with TS (Baizabal-Carvallo et al., 2023). Video recordings were acquired during scans to obtain timings of movements.

Analysis: fMRI data was distortion corrected using FSL-TOPUP and thermal noise was removed using NORDIC (Andersson et al., 2003; Vizioli et al., 2021). The resulting de-noised datasets were pre-processed and put through first-level analyses using FSL-FEAT (FMRI Expert Analysis Tool; Jenkinson et al., 2012), which included registration, high-pass temporal filtering, spatial smoothing, normalisation, and motion correction. A dataset was removed if absolute motion displacement was >2.5mm, leaving 9 TS and 12 HC datasets for the blink task, 9 TS and 10 HC datasets for the grimace task, and 10 TS and 11 HC datasets for the jaw clench task.

A mixed-effects analysis was used to average responses in TS and HC groups for each block (blink, grimace, or jaw clench). Results were masked to cover bilateral supplementary motor areas (SMA) and bilateral pre- and post-central gyri as defined by the Harvard-Oxford Cortical Structural atlas, before applying cluster correction determined by a Z-threshold of 2.3 (p = 0.05; Worsley, 2001).

Significant cluster activations were identified across the bilateral SMA and pre- and post-central gyri for blink, grimace, and jaw clench blocks in both the HC and TS groups (Figure 1; Z=2.3, p<.05). However, these clusters did not significantly differ between groups suggesting similar activations within the bilateral SMA and pre- and post-central gyri across groups.

This data suggests that functional mapping of facial movements (blinking, grimacing and jaw clenching) are not altered in TS.

Neurodevelopmental/ Early Life (eg. ADHD, autism) ¹

Activation (eg. BOLD task-fMRI) ²

FUNCTIONAL MRI

Motor

Movement Disorder

Tourette's Syndrome