Autistic brain seen to recall letters differently

A new brain-imaging study suggests that people with autism use different parts of the brain when remembering letters - regions normally associated with processing shapes rather than language.

The study, published online by the journal Neuroimage, also found that compared with other adults, autistic individuals showed less synchronization among certain brain regions while performing the letter-recall task.

According to the study authors, the findings support their theory that autism involves an underdevelopment of the complex circuitry that allows different brain areas to work together.

Autism is a developmental brain disorder that impairs, to varying degrees, a person's use of language and ability to communicate, interact socially and form relationships.

In addition, some people with autism excel at "detailed" tasks but have trouble performing more complex ones. They might do well when it comes to spelling words, for example, yet be unable to grasp the overall meaning of something they read.

The new study tested the idea that autistic individuals may process letters in parts of the brain associated with "lower-level" analysis of features - such as the recognition of shapes - while showing underactivity in brain areas involved in "higher-level cognition," such as that used in processing language.

Researchers led by Dr. Marcel Just of Carnegie Mellon University in Pittsburgh used an imaging technique called functional MRI to map brain activity in 14 adults with autism and 14 healthy adults. The autistic participants were considered "high-functioning," and had IQs similar to those of the comparison group.

The researchers analyzed patterns of brain activation while the study participants performed tasks in which they had to remember "target" letters and press a button when they saw them. They found that while both groups performed well, they showed different patterns of brain activity during the tasks.

Compared with the healthy adults, those with autism showed greater activation in some areas in the brain's right hemisphere associated with nonverbal information, but less activation in left-hemisphere regions involved in processing language.

In addition, they showed activity in certain areas in the back of the brain that help process lower-level visual-spatial information, whereas the healthy adults had very little activation in these regions.

Taken together, Just and his colleagues conclude, the results suggest that people with autism use a nonverbal, visual approach to processing letters.

"The language pattern in autism is a microcosm for the disorder," Just said in a statement. "People with autism are good at a lower level of analysis but have a deficit at the higher level."

He and his colleagues also found that the autistic adults had a lower level of synchronization among certain brain regions during the letter-recall tasks. This, they say, supports a theory they recently proposed holding that people with autism may have less "functional connectivity" among different brain areas, forcing each area to work more independently.