newsweek: Sibling Studies Shed New Light on Autism - 90% from genes???

[Guest guest]

Sibling Studies Shed New Light on Autism

By studying the siblings of kids with autism, researchers hope to develop

new methods for diagnosing the disorder. The mysteries of social

referencing.

WEB EXCLUSIVE

By Anne Underwood

Newsweek

Updated: 12:38 p.m. MT May 4, 2007

http://www.msnbc.msn.com/id/18492747/site/newsweek/

May 4, 2007 - While many parents of children with autism want to know more

about the possible role of environmental factors in the development of the

condition, scientific studies show that perhaps as much as 90 percent of

the risk comes from genes. Autism is highly heritable, an observation

underscored by the fact that, among the younger siblings of kids with

autism, roughly 10 percent will also develop the disorder. But what about

the other 90 percent? " They're the ones that interest us, " says

Dobkins, professor of psychology at the University of California, San

Diego. Their quirky behavior is not enough to qualify for a diagnosis of

autism, but " they still show atypical patterns of social interaction and

communication, " she says. What's going on in their brains? And can it

yield any clues that might help lead to earlier diagnosis for those with

the full-blown autism?

This week, Dobkins and her colleague Carver unveiled two joint

studies at the International Meeting for Autism Research that, in

different ways, help to chip away at those questions. In one of the

studies, the pair looked at social behaviors; in the other, at sensory

perceptions. But both are highly revealing.

The first of the studies examined a behavior known as " social

referencing " —or the tendency to look to others to help read meaning into

an unfamiliar event. Dobkins explains it this way. " Say, you've never

flown in an airplane before and it starts bouncing around, " she says.

You're not sure if this means you've hit a rough patch or the plane is

about to nosedive. " So you look around at your fellow passengers, " she

says. " If they're screaming, you think, 'This is bad. I have to start

screaming, too'. " This behavior is very common. Children usually begin

doing it around 12 months of age, checking for mom's smile of approval

before investigating a new caterpillar in the park, for example.

But in a study of 20 " high-risk " toddlers (18-month-old children with an

autistic older sibling), Carver and Dobkins showed that the

social-referencing behavior of these children was very different from that

of a control group of 16 children the same age with no autism in the

family. They put each child into a room with a parent, a researcher (who

was a stranger) and a series of novel mechanical toys—a spider with eyes

that light up and flash, a raccoon that pushes a ball around the room with

its nose, and a dinosaur that walks in circles and beeps. Both groups

stared intently at the toys for a good 30 seconds or so before looking up

at the parent for cues as to how to interpret these puzzling creatures.

But the children with no autism in the family looked at the stranger 2.5

times more often than the high-risk children did. Why? Carver speculates:

" The high-risk toddlers might be comfortable with their moms, but less

comfortable with a complete stranger. "

Even more intriguing was their response to the cues from the adults. When

the stranger registered delight or disgust or showed no particular emotion

at all, the children in the control group responded accordingly, reacting

more positively to a toy " tagged " with a positive emotion, more negatively

to one that drew negative responses from the adult stranger. But the

high-risk toddlers simply ignored the cues. " There was no match of

emotions, " says Carver. " Again, we think that one of the things in autism

is being able to read emotions, know what they mean and apply them to

social situations. "

That's not all the study revealed. The toddlers all wore caps with tiny

electrodes embedded in them to record brain waves—and those, too, showed

differences. The control-group children had three different types of

brain-wave responses, depending on the emotions the researcher

displayed—positive, negative or neutral. But the high-risk children showed

identical patterns of brain activity in response to all three. This is

particularly interesting, says Carver, because these are not children that

have been identified as quirky or problematic or anything but normal. Yet

there are clearly differences there. " We often note that adult family

members of kids with autism don't like big crowds or avoid parties or

prefer to work with data than people, " she says. None of these behaviors

constitutes a diagnosis. " But it shows social inhibition " —and that may run

in families.

At this stage, Carver and Dobkins are unable to interpret the data finely

enough to predict which of these high-risk children will be in the unlucky

10 percent who develop autism. But the hope is that by continuing to

follow these children out to an age where a diagnosis is possible, they

will then be able to look back at the earlier data and see if certain

characteristic patterns were indicators of trouble ahead. Currently, a

child can be diagnosed by the age of 3—although many are not diagnosed

until about 5. This line of inquiry could conceivably lead to the ability

to diagnose children as early as 18 months.

There are other potential early clues beyond social referencing. In the

second of the studies, Dobkins and Carver looked at responses to one type

of sensory information— " low-level visual sensitivity, " or the ability

simply to detect contrast between light and dark. " Children with autism

are often more sensitive to sensory stimuli, " says Dobkins. " Noises are

too loud. Things they touch feel weird. Visual stimuli are too great. We

began thinking, maybe we can find traits that are simpler than social

interaction and communication, but still closely tied to the genes

underlying the disorder. " These might be even easier to detect earlier.

Dobkins and Carver took 13 high-risk infants at 6 months of age and 26

control infants from families free of autism and showed them a split

computer screen. One side of the screen was blank. The other showed a

series of blurry stripes against a background providing low, medium or

high contrast. Because babies prefer to look at an image rather than a

blank screen, the experimenter would follow the child's gaze to determine

the threshold at which he or she could begin to detect the emerging

contrast levels. The high-risk infants were nearly twice as sensitive as

control infants. Since the brain structures used for low-level visual

perception feed into higher-level structures used for seeing and

recognizing faces, these early, low-level perceptual differences may be

indicative of changes that will come later in higher-level processing. The

results, say Dobkins and Carver, are further evidence that " autism is a

biological-developmental disorder " and that " to understand it, we will

need to understand the development of the brain across time. "

Ultimately, there is no single brain region that will tell the whole

story, and other researchers at the conference are focusing on different

areas. Mirella Dapretto of UCLA presented a study on the response of

so-called " mirror neurons " —those brain cells that help you mimic another

person's body movements and facial expressions and, in doing so, feel

empathy by figuratively putting yourself in that person's shoes. Mirror

neurons help explain why one crying toddler can set off others nearby,

starting one loud, communal wail. Dapretto began with interviews and

questionnaires to gauge how readily 12 children aged 9 to 16 with

high-functioning autism imitated others and empathized with them. Using

sophisticated brain imaging, she then measured activity in the

mirror-neuron brain areas of these children as they looked at pictures of

faces that were happy, sad, angry, fearful or neutral. Those with the

lowest empathy scores also had the least activity in the mirror-neuron

areas. That doesn't mean these children are helpless in social situations.

Because they're high-functioning, Dapretto says, they have learned to

distinguish different expressions—though they may do so through a series

of deliberate calculations rather than the automatic way a normal child

would. The interesting part is that the difference shows up as a different

pattern of brain activity, even though the end result is the same—being

able to recognize the expressions.

Taken together, says Carver, these studies show that " if you want a solid

picture, you will need to look at the development of the whole brain and

interaction between affected areas. " When researchers are able to do that,

they will be much closer to a full understanding of this tragic disorder.

URL: http://www.msnbc.msn.com/id/18492747/site/newsweek/

© 2007 MSNBC.com

The material in this post is distributed without

profit to those who have expressed a prior interest

in receiving the included information for research

and educational purposes.For more information go to:

http://www4.law.cornell.edu/uscode/17/107.html

http://oregon.uoregon.edu/~csundt/documents.htm

If you wish to use copyrighted material from this

email for purposes that go beyond 'fair use', you

must obtain permission from the copyright owner.