New understanding of sensory overload in autism

New understanding of sensory overload in autism

New research shows that people with autism have enhanced movement integration that can make them better or worse at seeing motion, depending on what they are asked to do.

This challenges previous research showing that people with autism generally see visual motion poorly.

This increased ability to pool motion information, in combination with fewer restraints on perception, may be one of the causes of “sensory overload” for sufferers of Autism Spectrum Disorder, says University of Auckland scientist, Professor Steven Dakin.

Professor Dakin contributed to a just published research paper in the Journal of Neuroscience that outlines these findings. The research was undertaken together with autism researchers from University College, London.

“Our understanding of visual processing in autism has been obscured by the use of tests that don’t really tell us what limits people’s visual performance,” says Professor Dakin who leads the School of Optometry and Vision Science at the University of Auckland.

“The accepted view is that people with autism do local processing (the fine detail of the world), but they can’t do global processing (the overall context),” he says. “For the first time we now have a way of separating these two functions in the lab.

“When we apply it to children with autism, we find they don’t have a global processing problem at all. If anything, they are better at global processing ,” he says.

“The assumption was that if you are bad at tasks that require pooling information it is because you can’t pool it. Now we think that what’s happening is that people with autism can’t ignore irrelevant information and that’s quite a different thing.

“That’s about your ability to resist noise, and so we think it’s related to sensory overload. Their sensory overload is an inability to resist the irrelevant,” says Professor Dakin.

“If anything, you could almost think of that as more integration – the exact opposite of what people have thought. Our work shows that integration is fine in people with autism, they just can’t ignore noise.”

He says for example, when someone wants to judge the overall direction of a shoal of fish or a crowd of people, they must integrate motion signals across space and time. This is usually tested using a standard ‘motion coherence paradigm’ in which people report the direction of coherently moving dots amid randomly moving noise dots.

“Poor performance by autistic individuals on this task has been widely interpreted as evidence of disrupted integrative processes, but critically, motion coherence is not limited only by the ability to pool information,” says Professor Dakin.

“Itcan also be limited by a lack of precision estimating the direction of elements or by difficulties separating motion signals from ‘noise’,” he says.

The study tested 33 children with autism and 33 ability matched typical children on a more robust task – reporting mean direction, both with and without directional variability.

Professor Dakin says the inability to deal with noise may apply in other aspects of Autism Spectrum Disorders such as other sensory systems and cognitive functions.

“If we have a better understanding of how these things work, then we can develop better approaches for dealing with them, such as in the way we present information to people with ASD, and the way we train people to improve their performance in these areas,” he says.

“For the first time the technique that we have developed experimentally is unambiguous about what is driving that performance. The reason that we can be so confident is because we have a report of better behaviour and that’s rare and more diagnostic than worse behaviour (which can have many causes). “

Professor Dakin, who has researched this area for more than 15 years, says his input into the research is the experimental technique that the group is using.

“It’s one that I’ve developed over many years, both in London and in Auckland, which can measure people’s ability to combine information to make sense of our complex visual world,” he says.

ENDS

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