The symptoms experienced by people with Tourette syndrome often get worse in social situations. New research at BSMS suggests that the reason may be because the brains of people with Tourette syndrome are hyper-responsive to social cues, including emotional facial expressions.
Research Fellow Dr Charlotte Rae, who conducted the study, said: "People with Tourette syndrome often report that their tics get worse in stressful social situations where they are under public scrutiny. Now for the first time, functional MRI scanning has shown how this is probably occurring – through an increase in activity in the insula, and the signals this then sends to the areas of the brain that cause tics. This understanding may help us to work on new therapies for people with Tourette syndrome, by developing ways to manage the increase in insula activity in such scenarios."
Tourette syndrome is a neurological condition that begins in childhood and may be lifelong in which people make many ‘tics’, which are involuntary movements and sounds. People with Tourette syndrome can learn to suppress tics for a while but this is effortful. Tics are often made worse by stress, including social situations, where the actions and facial expressions of other people may trigger them.
The researchers scanned the brains of 21 people with Tourette syndrome and 21 control participants without tics while they watched pictures of faces depicting emotions such as anger. Both groups demonstrated activation within visual brain areas, including the fusiform face area, which shows strong activity when people look at faces. In addition, those with Tourette syndrome also showed extra responses in the insula. This brain region also showed much greater signalling with brain regions that control movement and are implicated in generating tics: the pre-supplementary motor area, premotor cortex, primary motor cortex and the putamen.
The strength of communication between the insula and deep (subcortical) brain areas (thalamus and globus pallidus) predicted the severity of tics and Tourette symptoms, while insular communication to upper (cortical) brain areas (supplementary motor area) varied in proportion to uncomfortable feelings of ‘itch’ or ‘pressure’ that occur just before tics (premonitory sensations).
According to Chair of Psychiatry at BSMS, Prof Hugo Critchley, the study findings may help develop better ways for people with Tourette syndrome to manage their symptoms: "We are getting a clearer insight into the brain basis of tics that now incorporates the science of emotion and social interaction. By unpicking these mechanisms, we can fine-tune treatment approaches. Until now, we have tended to rely on medicines to inhibit movements or decrease compulsions in Tourette syndrome, but these often have unwanted side-effects and may not be particularly effective. This research leads the way toward more individualised approaches that get closer to the psychosocial triggers to tics and the neurology of Tourette symptoms."
The study has been published in the journal Brain. Illustration by Lottie Clarke.
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