|Researchers Gain Insight Into Why Brain Areas Fail To Work
Together in Autism
Basis 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 Alexander, 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
Nancy 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
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/new/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.
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
“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
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.
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
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
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 Institute’s Web site at http://www.nichd.nih.gov/.
The National Institutes of Health (NIH) — The Nation's Medical Research
Agency — includes 27 Institutes and Centers and is a component of
the U.S. Department of Health and Human Services. It is the primary federal
agency 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 www.nih.gov.