Why people with autism Think in Pictures

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Researchers Gain Insight Into Why Brain Areas Fail To Work Together in Autism

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Last Update: 08/22/2006 Printer Friendly Email This

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National Institute of Child Health

and Human Development (NICHD)

July 12, 2006

Researchers Gain Insight Into Why Brain Areas Fail To Work

Together in Autism

Basis Identified For Why People With Autism Think In Pictures

Researchers have found in two studies that autism may involve

a lack of connections and coordination in separate areas of the brain.

In people with autism, the brain areas that perform complex

analysis appear less likely to work together during problem solving tasks than

in people who do not have the disorder, report researchers working in a network

funded by the National Institutes of Health. The researchers found that

communications between these higher-order centers in the brains of people with

autism appear to be directly related to the thickness of the anatomical

connections between them.

In a separate report, the same research team found that, in

people with autism, brain areas normally associated with visual tasks also

appear to be active during language-related tasks, providing evidence to explain

a bias towards visual thinking common in autism.

" These findings provide support to a new theory that views

autism as a failure of brain regions to communicate with each other, " said Duane

, M.D., Director of NIH's National Institute of Child Health and Human

Development. " The findings may one day provide the basis for improved treatments

for autism that stimulate communication between brain areas. "

The studies and the theory are the work of Marcel Just, Ph.D.,

D.O. Hebb Professor of Psychology at Carnegie Mellon University in Pittsburgh,

Pennsylvania, and Minshew, M.D., Professor of Psychiatry and Neurology at

the University of Pittsburgh School of Medicine and their colleagues.

The research was conducted by the Collaborative Program of

Excellence in Autism, a research network funded by the NICHD and the National

Institute on Deafness and Other Communication Disorders.

People with autism often have difficulty communicating and

interacting socially with other people. The saying " unable to see the forest for

the trees " describes how people with autism frequently excel at details, yet

struggle to comprehend the larger picture. For example, some children with

autism may become spelling bee champions, but have difficulty understanding the

meaning of a sentence or a story.

An earlier finding by these researchers described how a group

of people with autism tended to use parts of the brain typically associated with

processing shapes to remember letters of the alphabet. A news release detailing

that finding appears at http://www.nichd.nih.gov/news/releases/final_autism.cfm.

Participants with autism in both current studies had normal

I.Q. There were no significant differences between the participants with and

without autism in age or I.Q.

The first of the two new studies recently was published online

in the journal Cerebral Cortex. In that study, the researchers used a brain

imaging technique known as functional magnetic resonance imaging, or fMRI, to

view the brains of people with autism as well as a comparison group of people

who do not have autism. All of the study participants were asked to complete the

Tower of London test. The task involves moving three balls into a specified

arrangement in an array of three receptacles. The Tower of London is used to

gauge the functioning of the prefrontal cortex.

This brain area, located in the front, upper part of the

brain, deals with strategic planning and problem-solving. The prefrontal cortex

is the executive area of the brain, in which decision making, judgment, and

impulse control reside.

A little further back is the parietal cortex, which controls

high-level visual thinking and visual imagery, supporting the visual aspects of

the problem-solving. Both the prefrontal and parietal cortex play a critical

part in performing the Tower of London test.

In the normal participants, the prefrontal cortex and the

parietal cortex tended to function in synchrony (increasing and decreasing their

activity at the same time) while solving the Tower of London task. This suggests

that the two brain areas were working together to solve the problem.

In the participants with autism, however, the two brain areas,

prefrontal and parietal, were less likely to function in synchrony while working

on the task.

The researchers made another discovery, for the first time

finding a relationship between this lower level of synchrony and the properties

of some of the neurological " cables " or white matter fiber tracts that connect

brain areas.

White matter consists of fibers that, like cabling, connect

brain areas. The largest of the white matter tracts is known as the corpus

callosum, which allows communication between the two hemispheres (halves) of the

brain.

" The size of the corpus callosum was smaller in the group with

autism, suggesting that inter-regional brain cabling is disrupted in autism, "

Dr. Just said.

In essence, the extent to which the two key brain areas

(prefrontal and parietal) of the autistic participants worked in synchrony was

correlated with the size of the corpus callosum. The smaller the corpus

callosum, the less likely the two areas were to function in synchrony. In the

normal participants, however, the size of the corpus callosum did not appear to

be correlated with the ability of the two areas to work in synchrony.

" This finding provides strong evidence that autism is a

disorder involving the biological connections and the coordination of processing

between brain areas, " Dr. Just said.

He added, however, that the thickness, or extent, of

connections between brain areas may not be the basis for the disorder. Although

the neurological connections between the prefrontal cortex appear to be reduced

in autism, the brains of people with autism have thicker connections between

certain brain regions within each hemisphere.

" At this point, we can say that autism appears to be a

disorder of abnormal neurological and informational connections of the brain,

but we can't yet explain the nature of that abnormality, " Dr. Just said.

In the second study, published online in the journal Brain,

the researchers examined the extent to which brain areas involved in language

interact with brain regions that process images. Dr. Just explained that earlier

studies, as well as anecdotal accounts, suggest that people with autism rely

more heavily on visual and spatial areas of the brain than do other people.

In this study, the researchers used fMRI to examine brain

functioning in participants with autism and in normal participants during a

true-false test involving reading sentences with low imagery content and high

imagery content. A typical low imagery sentence consisted of constructions like

" Addition, subtraction, and multiplication are all math skills. " A high imagery

sentence, " The number eight when rotated 90 degrees looks like a pair of

eyeglasses, " would first activate left prefrontal brain areas involved with

language, and then would involve parietal areas dealing with vision and imagery

as the study participant mentally manipulated the number eight.

As the researchers expected, the visual brain areas of the

normal participants were active only when evaluating sentences with imagery

content. In contrast, the visual centers in the brains of participants with

autism were active when evaluating both high imagery and low imagery sentences.

" The heavy reliance on visualization in people with autism may

be an adaptation to compensate for a diminished ability to call on prefrontal

regions of the brain, " Dr. Just said.

The second study also confirmed the observations in the first

study-that the prefrontal and parietal brain regions of the cortex in people

with autism were less likely to work in synchrony than were the brains of normal

volunteers. The second study also confirmed that the extent to which the two

parts of the cortex could work together was correlated with the size of the

corpus callosum that connected them.

Dr. Just and his colleagues are conducting additional studies

to ascertain the nature of the abnormality of the connections in the brains of

people with autism.

###

The NICHD sponsors research on development, before and after

birth; maternal, child, and family health; reproductive biology and population

issues; and medical rehabilitation. For more information, visit the Web site at

http://www.nichd.nih.gov/.

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for conducting and supporting basic, clinical, and translational medical

research, and it investigates the causes, treatments, and cures for both common

and rare diseases. For more information about NIH and its programs, visit

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