Children with Autism: Senses of sight and sound separated

Like watching a foreign movie that was badly dubbed, children with autism spectrum disorders (ASD) have trouble integrating simultaneous information from their eyes and their ears, according to a Vanderbilt study published today in The Journal of Neuroscience.

Mark Wallace

The study, led by Mark Wallace, Ph.D., director of the Vanderbilt Brain Institute, is the first to illustrate the link and strongly suggests that deficits in the sensory building blocks for language and communication can ultimately hamper social and communication skills in children with autism.

"There is a huge amount of effort and energy going into the treatment of children with autism, virtually none of it is based on a strong empirical foundation tied to sensory function," Wallace said.

"If we can fix this deficit in early sensory function then maybe we can see benefits in language and communication and social interactions."

And the findings could have much broader applications because sensory functioning is also changed in developmental disabilities such as dyslexia and schizophrenia, Wallace said.

In the study, Vanderbilt researchers compared 32 typically developing children ages 6-18 years old with 32 high-functioning children with autism, matching the groups in virtually every possible way including IQ.

Study participants worked through a battery of different tasks, largely all computer generated.

Researchers used different types of audiovisual stimuli such as simple flashes and beeps, more complex environmental stimuli like a hammer hitting a nail, and speech stimuli, and asked the participants to tell them whether the visual and auditory events happened at the same time.

The study found that children with autism have an enlargement in something known as the temporal binding window (TBW), meaning the brain has trouble associating visual and auditory events that happen within a certain period of time.

Stephen Camarata

"Children with autism have difficulty processing simultaneous input from audio and visual channels. That is, they have trouble integrating simultaneous information from their eyes and their ears," said co-author Stephen Camarata, Ph.D., professor of Hearing and Speech Sciences. 

"It is like they are watching a foreign movie that was badly dubbed, the auditory and visual signals do not match in their brains."

A second part of the study found that children with autism also showed weaknesses in how strongly they "bound" or associated audiovisual speech stimuli.

"One of the classic pictures of children with autism is they have their hands over their ears," Wallace said.

"We believe that one reason for this may be that they are trying to compensate for their changes in sensory function by simply looking at one sense at a time. This may be a strategy to minimize the confusion between the senses."

Wallace noted that the recently-released Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, (DSM-5), which serves as a universal authority for psychiatric diagnosis, now acknowledges sensory processing as a core deficit in autism.

US DSM-5 for diagnosing mental disorders published - Asperger's is Out!

In the manual, grief is newly medicalised as major depressive disorder (MDD). 

Credit: Adam G. Gregor /Alamy

The field of mental health will face its greatest upset in years on Saturday with the publication of the long-awaited and deeply-controversial US manual for diagnosing mental disorders.

Early drafts of the book, the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5, have divided medical opinion so firmly that authors of previous editions are among the most prominent critics.

Known informally as the psychiatrists' bible, the $199 tome from the American Psychiatric Association is the guidebook that US doctors will use to diagnose mental disorders. The latest edition is the first major update in 20 years.

Though not used in the UK, where doctors turn to the World Health Organisation's International Statistical Classification of Diseases (ICD), the US manual has global influence. It defines groups of patients, and introduces new names for disorders.

Those names can spread, and become the norm elsewhere, but more importantly, the categories redefine the populations that are targeted by drugs companies.

Criticisms have come from almost every corner. There are claims of expansionism, with common experiences and behaviours becoming newly medicalised.

Allen Frances

Temper tantrums become Disruptive Mood Dysregulation Disorder (DMDD); grief becomes major Depressive Disorder (MDD), according to Allen Frances, an American psychiatrist who chaired the task force behind the fourth edition of the manual.

Other behaviours get their own labels: overeating becomes binge eating disorder; keeping too much junk, a hoarding disorder; a bit forgetful could be mild neurocognitive disorder.

David Clark

David Clark, professor of experimental psychology at Oxford University, said "Mental health disorders are often hard to divide into clear categories, because too little is known about them, and there can be major overlaps. But the definitions are often valuable. For example, greater distinctions between various types of anxiety have led to more specific and effective treatments."

Nick Craddock, professor of psychiatry at Cardiff University, and director of the National Centre for Mental Health in Wales, said "Some of the stranger aspects of the US manual will have no impact in Britain. DSM-5 was flawed because definitions of disorders were sometimes changed on the basis of too little fresh scientific evidence."

"I don't believe the science has advanced sufficiently in 20 years since DSM-4 to warrant making a new system," he said. "That essentially is just a group of people agreeing on tweaking things and making them appear a little bit different. That to me is not a very helpful stage in the develop of psychiatric diagnosis. This is the wrong time in history to change the diagnostic system."

Changing the definitions of disorders alters who has them. That affects who gets drugs and other support, and who interventions are trialled on. If the criteria for attention Deficit Hyperactivity Disorder (ADHD) are broadened, then more people are likely to be diagnosed with the condition.

The arrival of DSM-5 will mean the end of Asperger's syndrome in the professional eyes of the US psychiatric arena.

Along with some other autism-related conditions, Asperger's will now be consumed by the new category of "autism spectrum disorder".

Carol Povey

Some people diagnosed with Asperger's are unhappy about the coming change. Carol Povey, director of the National Autistic Society's Centre for Autism, said: "The term Asperger Syndrome is a core part of their identity for many people and they understandably feel anxious about moves to remove the term. The changes won't prevent people from continuing to use it to define themselves and nor should it," she said.

Debbie Tucker, chair of the Asperger's Syndrome Foundation, said the label can be useful in treating people, but that some did not want to be labelled. "Labels only become unhelpful and sometimes dangerous if used to discriminate. People with Aspergers are vulnerable to this," she said.

Thomas Inse

Last month, Thomas Insel, director of the National Institute of Mental Health, declared that the organisation would not use DSM-5 definitions to set its research priorities. Writing about DSM-5 on his blog, he said: "The weakness is its lack of validity. Unlike our definitions of ischaemic heart disease, lymphoma, or AIDS, the DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure."

Instead, he said the NIHM would lay the foundations for a new classification system, based on brain imaging, genetics, cognitive science and other research.

"We need to begin collecting the genetic, imaging, physiologic, and cognitive data to see how all the data – not just the symptoms – cluster and how these clusters relate to treatment response," he said.