Differing Brain Connections May Cause Autism’s Social Impairment

The brains of adults with autism may be "wired" differently from people without the disorder, and this abnormal pattern of connectivity may be responsible for the social impairments that are characteristic of autism.

Using functional magnetic resonance imaging, a team of researchers affiliated with the University of Washington’s Autism Center found that the most severely socially impaired subjects in the study exhibited the most abnormal pattern of connectivity among a network of brain regions involved in face processing.

"This study shows that these brain regions are failing to work together efficiently," said Natalia Kleinhans, a research assistant professor of radiology and lead author of the paper published in the journal Brain. "Our work seems to indicate that the brain pathways of people with autism are not completely disconnected, but they are not as strong as in people without autism."

The study is the first to look at brain connectivity and social impairment, and focused on how the brain processes information about faces. Deficits in face processing are one of the earliest characteristics to emerge in people with autism.

The research team led by Elizabeth Aylward, a UW professor of radiology, examined connectivity in the limbic system, or the network of brain regions that are involved with processing social and emotional information.

Participants in the study included 19 high-functioning adults with autism who had IQs of at least 85. They ranged in age from 18 to 44 and were compared with an age- and intelligence-matched sample of 21 typically developed adults.

The group with autism spectrum disorder included eight individuals diagnosed with autism, nine with Asperger’s syndrome and two diagnosed with pervasive developmental disorder not otherwise specified. The level of social impairment for each autistic participant was drawn from records of clinical observations and diagnoses that confirmed that each had autism.

Each participant had his or her brain scanned while looking at pictures of faces or houses. Participants were shown four series of 12 pictures of faces and a similar number of series showing houses. Each individual picture was seen for three seconds. Occasionally the same face or house picture was repeated, and participants were told to press a button when this occurred.

There was no significant difference on the two groups’ performance, because the task was so basic, said Todd Richards, a professor of radiology and co-author of the paper. "Differences might have shown up if they had been asked to do something more complicated."

However, the two groups exhibited different patterns of brain activity. The researchers focused on the fusiform face area of the brain, a region that is involved in face identification. Compared to the participants with autism, the typically developing adults showed significantly more connectivity between the fusiform face area and two other brain regions, the left amygdala and the posterior cingulate. In addition, autistic participants who had the largest social impairment showed the lowest level of connectivity between the right fusiform face area and the left amygdala and increased connectivity between the right fusiform face area and the right inferior frontal gyrus.

"This study shows that the brains of people with autism are not working as cohesively as those of people without autism when they are looking at faces and processing information about them," said Kleinhans.

Source: University of Washington, June 12, 2008

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  1. quiact says

    Thoughts Regarding Autism Spectrum Neurodevelopmental Disorders

    Of these rare neurological disorders, Autism is the most common. The autism spectrum reflects the broad range of symptoms in which the names of these autism disorders have been given their own name for their disorder.
    Autism is a disability that is suspected to be caused possibly by a brain development disorder of unknown etiology. Others suspect the cause is some sort of neurological dysfunction- possibly with a genetic predisposition. Autism is about 3 times more common in males than females as well, and it is unclear as to why this occurs.
    Usually, symptoms of the disease present themselves before the toddler reaches the age of three. Before Autism was more understood, others inaccurately labeled autistic people as childhood schizophrenia or as having a psychosis or mental retardation.
    Symptoms of the autistic patient included limited or dysfunctional social and personal or intimate relationships with others, their intelligence is affected, and the autistic person typically is adverse to change. Also, the autistic person tends to be compulsive and prefers to be alone. They lack eye contact as much as physical contact with other people.
    Out of over two dozen diagnostic criteria utilized for these disorders, eight must be present to be considered autistic, according to the DSM. As with all passive developmental disorders, the person expresses language, social, and behavioral difficulties.
    Treatment includes what are called psychotropic medications that delay the progression of the disorder, as well as relieve some of the symptoms of one who is autistic. Behavioral therapy is common as a treatment regimen as well. Boys get Autism much more than girls.
    Then there is the controversy between many who claim that thimerosal- a preservative containing mercury, which is a neurotoxin that was used in vaccines until 2001, was the catalyst for autism in children.
    Over 5000 lawsuits have been filed because of this belief, and some have been successful for the plaintiff. Yet most agree the correlation between thimersal and autism is void of scientific merit. Furthermore, the cases of autism have not decreased since the preservative was discontinued in 2001.
    Aside from Autism, the other four passive developmental disorders are known as autism spectrum disorders.
    Asperger’s Syndrome is more common than autism, and the symptoms are milder, as there is minimal delay in language abilities, if at all. What is expressed with Asperger’s syndrome is mild autistic symptoms. In time, the patient may express atypical personality disorders, though.
    While intelligence is within normal limits with the Asperger’s patient, social interactions and abilities preset difficulty for such a patient. As with Autism, medications and behavioral therapy are treatment regimens with one with this syndrome
    Rett’s Syndrome or disorder presents with not only atypical behavior, but also suffers from restricted physical growth and movement. There is cognitive and social impairment as well. The disorder affects mostly girls, and the cause is due to a gene mutation.
    Childhood Disintegrative disorder is rare, and is 10 times less common than autism. The disorder has a late onset with mild autistic symptoms. The disorder affects mostly boys, and regression is sudden and possible with this disorder. Skills lost with this disorder may be language, social, self-care, as well as play or motor skills. Decreased function or impairment with this disorder may include social skills and behavioral flaws. Central Nervous System pathology is a suspected cause of this disorder.
    Finally, there are passive development disorders that are not otherwise specified. This may include atypical autism, for example. Yet as with the rest of types of these disorders, the symptoms vary in their frequency and intensity, as well as the range of abilities of these developmental disorders vary widely as well.
    Medicinal treatment is believed to be not necessary for the management of all of those who may have autistic spectrum disorders. Depending on the patient’s health care provider, medications may be prescribed by their doctor to manage any affective disorders autistics may present in an acute or chronic nature. However, cognitive and behavioral therapy prove to be most beneficial for all the different types of Passive Development Disorders that exist for reasons yet to be defined.
    http://www.autism-society.org
    http://www.medicalnewstoday.com/articles/139183.php
    Dan Abshear

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