New findings of research into Tourette syndrome could help to pinpoint the cause of the condition.

University of Nottingham researchers have found evidence for an unexpected conclusion — that people with Tourette syndrome actually have more control over some brain processes than people unaffected by the condition.

It has been a widely held view that Tourette — a condition that affects thousands of Britons and can seriously inhibit social interaction — is the result of the failure of control systems in the brain.

Though the repetitive vocal and physical tics characteristic of Tourette suggest an inability to control involuntary actions at the cognitive level, the latest findings contradict this and suggest the opposite may be the case. The Nottingham researchers have found evidence that young people with Tourette’s syndrome actually exhibit a greater level of cognitive control over their movements and speech than their non-affected peers do.

The constant need to suppress tics may have enhanced the brain processes that normally inhibit unwanted movement and speech, researchers believe.

The research findings offer new clues as to which regions of the brain may be involved in the generation of the syndrome’s characteristic behavioural tics. Dr Georgina Jackson and colleagues at The University of Nottingham report their findings in the March 21 issue of the journal Current Biology.

Tourette syndrome is a developmental disorder that typically occurs during late childhood and is characterised by the presence of chronic vocal and physical tics. Tics are involuntary, repetitive, highly stereotyped behaviours that occur with a limited duration, typically occur many times during a single day, and occur on most days.

Physical tics can be simple or complex in appearance, ranging from simple repetitive movements to coordinated action sequences. Verbal tics may involve repeating words or utterances (known as palilalia), producing inappropriate or obscene utterances (coprolalia), or the repetition of another’s words (echolalia).

Understanding the psychological processes and neural mechanisms that give rise to the execution of tics is of considerable clinical importance. A widely held view is that the inability to suppress unwanted movements in Tourette’s syndrome results from a failure of cognitive control mechanisms.

In the new work, Dr Jackson and colleagues studied cognitive control mechanisms in a group of young people with Tourette syndrome (TS) by assessing the performance of individuals on a goal-oriented eye-movement task.

The task demanded high levels of voluntary control and the active inhibition of automatic eye movements. The researchers found that in performing the task, TS individuals are not in fact impaired in cognitive control. Instead, the study showed that, paradoxically, TS individuals make fewer error responses than their age-matched and neurologically normal peers do, while responding just as fast to the task’s demands.

According to Dr Jackson and colleagues, this finding most likely reflects a compensatory change in TS individuals — whereby chronic suppression of tics results in a generalised suppression of reflexive behaviour in favour of increased cognitive control.

Dr Jackson said: “The findings are tremendously exciting and provide an important advance in our understanding of the behavioural consequences of Tourette’s syndrome.

“Our current work is using ultra high-field brain imaging (MRI) techniques to understand the neural correlates of these behavioural changes. We would like to thank the Tourette’s patients and their families for their continued help with our research programme.”

Abstract:

Enhanced Cognitive Control in Young People with Tourette's Syndrome

Sven C. Mueller1, Georgina M. Jackson1, , , Ranu Dhalla1, Sophia Datsopoulos1 and Chris P. Hollis1

1Division of Psychiatry, Queen's Medical Centre, The University of Nottingham, Nottingham NG7 2RD, United Kingdom

Received 26 October 2005; revised 12 January 2006; accepted 23 January 2006. Published: March 20, 2006. Available online 20 March 2006. Current Biology

Summary
Tourette's syndrome (TS) is a neurodevelopmental disorder characterized by the presence of chronic vocal and motor tics. Tics are sudden, highly stereotyped, movements that can be simple or complex in appearance. Since patients with TS have difficulties preventing unwanted movements, one might expect that their ability to voluntarily control goal-directed movements would be similarly poor. Indeed, it has been suggested that TS sufferers are impaired at inhibiting reflexively triggered movements and in rapidly selecting or switching between different motor sets [1]. This idea is consistent with current views on the neurological basis of TS that posit a dysfunction of the neural circuits linking the frontal lobes and the striatum [2]. These circuits are known to be involved in the voluntary control of action 3 and 4. By using an oculomotor switching task, we show for the first time that young people with TS exhibit paradoxically greater levels of cognitive control over their movements than their age-matched controls. This finding is consistent with an increased need to monitor and control movements and may indicate a subcortical locus for the triggering of tics. It also suggests that the constant need to suppress tics could have resulted in an enhancement of the executive processes involved in inhibitory control.