May 8, 2006

Autistic brains may daydream less

Neural networks used to self-reflect are dulled in autistics.

by Helen Pearson
Nature News

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Autistic patients may lack the ability to daydream normally, say researchers who have found that these people's brains act differently when they are taking a break.

Neuroscientists know that a certain network of brain regions fires up when our minds wander, and that this is important for pondering and reminiscing about ourselves, others and our emotions. Other studies have hinted that autistic patients, who have learning and social problems, might have abnormalities in this region but the details have been unclear.

To pin down whether autism is related to these brain changes, Daniel Kennedy of the University of California at San Diego, La Jolla, and his colleagues studied 15 adults with some form of autism and 14 healthy controls. The team used functional magnetic resonance imaging (fMRI) to scan the 'daydreaming' regions, which lie in the middle of the brain.

In healthy people, these spots become active when the brain is resting and dampen down when the brain is working hard at a mental puzzle, the researchers confirmed. They also showed that part of the network revs up when participants read emotional words, such as 'murder' or 'blood', compared with bland ones such as 'table'.

The team showed that those patients with a more abnormal pattern of activity in these regions tended to have greater social difficulties in real life. "This critically important area is not functioning the way it should," Kennedy says.

Time to ponder

The study suggests that this paralysed network could prevent a patient's brain from conjuring a normal internal picture of themselves and others, Kennedy says, and so interfere with social behaviour.

Alternatively, it may be the social problems that are somehow altering the brain network. One way to investigate this would be to look at the brains of young children before the first signs of autism arise, to see if the same regions are dampened.

Researchers have already found problems in this same resting network in patients with Alzheimer's disease, suggesting that this region may be particularly susceptible to disruption.

Autism is thought to be one of a spectrum of disorders in which people suffer varying degrees of difficulties in communication, social interactions, and in showing repetitive behaviour. The condition is estimated to affect between two and six children in every 1,000.

Quite what causes the disorders remains a topic of hot debate. Researchers know that the condition tends to run in families, which suggests that genes are involved. One recent discovery is that autistic children have brains that are larger and grow faster than those of other kids, perhaps setting up problems later on in life.

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