PEOPLE who swear and twitch because they have Tourette's syndrome are more in control of their actions than anyone realised. A psychologist in Canada has found the first direct evidence that their tics are intentional, coordinated movements made in response to some irresistible urge, rather than involuntary spasms.
The symptoms of Tourette's range from excessive twitching to extreme bouts of inappropriate swearing. Doctors have assumed that the tics and verbal outbursts are involuntary, says Randy Flanagan of Queen's University in Kingston, Ontario.
To test this, Flanagan and his colleagues studied the movements of a young man with Tourette's, "BF", by asking him to hold a small weighted box fitted with sensors that recorded his grip force and movements. The sensors measured how BF modified his grip on the box when asked to move his arm.
If the tics were spasmodic reflex actions, BF would not have time to adjust his grip during a tic. But the researchers found that he anticipated each tic and increased his grip, just as he and four subjects who did not have Tourette's did during voluntary movements (Experimental Brain Research, vol 128, p 69).
Flanagan believes this is evidence that Tourette's is not a simple motor disorder but a higher-level problem. He thinks it is like obsessive compulsive disorders, which affect the circuits of the brain's premotor frontal lobe and basal ganglia-areas that control planning and decision making.
Most people have the urge to say or do inappropriate things, but decide not to, says Flanagan. But Tourette's sufferers lack the ability to suppress these impulses. "It's probably an extreme variant of a normal thing felt by many people," he says.
"It's a nice observation," says John Rothwell, an expert on movement disorders at the Institute of Neurology in London. "It may tell us something about how the brain makes normal voluntary movements," he adds.
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Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-171-331-2751
New Scientist
8-Sep-1999