Autism is a mysterious developmental disease because it often leaves complex abilities intact while impairing seemingly elementary ones. For example, it is well documented that children with autism often have difficulty correctly using pronouns, sometimes referring to themselves as "you" instead of "I."
A new brain-imaging study by scientists at Carnegie Mellon University (CMU) provides an explanation as to why the use of the wrong pronoun is more than simply a word choice problem for this population (Brain, online, July 6, 2011).
Marcel Just, PhD, first author Akiki Mizuno and their collaborators at the CMU Center for Cognitive Brain Imaging (CCBI) found that errors in choosing a self-referring pronoun reflect a disordered neural representation of the self - a function processed by at least two brain areas, one frontal and one posterior.
"The psychology of self - the thought of one's own identity - is especially important in social interaction, a facet of behavior that is usually disrupted in autism," said Dr. Just, director of the CCBI. "Most children don't need to receive any instruction in which pronoun to use. It just comes naturally, unless a child has autism."
The researchers used functional magnetic resonance imaging (fMRI) to compare the brain activation pattern and the synchronization of activation across brain areas in young adults with high-functioning autism with control participants during a language task that required rapid pronoun comprehension.
The results revealed a significantly diminished synchronization in autism between the right anterior insula, a frontal area, and the precuneus, a posterior area, during pronoun use in the autism group. The participants with autism also were slower and less accurate in their behavioral processing of the pronouns.
In particular, the synchronization was lower in the subjects with autism between the two brain areas when answering a question that contained the pronoun "you" in querying something about the participant's view.
"Shifting from one pronoun to another, depending on who the speaker is, constitutes a challenge not just for children with autism but also for adults with high-functioning autism, particularly when referring to one's self," Dr. Just said. "The functional collaboration of two brain areas may play a critical role for perspective shifting by supporting an attention shift between oneself and others."
He added, "Pronoun reversals also characterize an atypical understanding of the social world in autism. The ability to flexibly shift viewpoints is vital to social communication, so the autistic impairment affects not just language but social communication."
Autism was documented for the first time in 1943 in a landmark article by Leo Kanner, MD, of Johns Hopkins University, who noted the puzzling misuse of pronouns by children with the disorder. "When he [the child] wanted his mother to pull his shoe off, he said: 'Pull off your shoe,'" Dr. Kanner wrote. "Personal pronouns are repeated [by the child with autism] just as heard, with no change to suit the altered situation."
Previous brain-imaging autism research by Dr. Just has shown that other facets of thinking disrupted in autism, such as social difficulties and language impairments, may be attributed to a reduced communication bandwidth between the frontal and posterior parts of the brain. He refers to this as the "Theory of Frontal-Posterior Underconnectivity." In each of these types of thinking, the processing is done by a set of different brain regions that includes key frontal regions. The lower frontal-posterior bandwidth limits how well the frontal regions can contribute to the networked computations of the brain.
The communication network of the brain is its white matter, which consists of myelinated axons that carry information between different regions. An emerging view is that the white matter is compromised in autism, specifically in the frontal-posterior tracts.
A groundbreaking 2009 study by Dr. Just and colleagues showed for the first time that compromised white matter in children with reading difficulties could be repaired with extensive behavioral therapy. The imaging study showed that the brain locations that had been abnormal prior to remedial training improved to normal levels afterwards. Reading performance also improved by an amount that corresponded to the amount of white matter change. Ongoing research at CCBI is assessing the white matter in detail, measuring its integrity and topology and trying to pinpoint the difference in the brain network of people with autism.
"This new understanding of what causes pronoun confusion in autism helps make sense of the larger problems of autism as well as the idiosyncrasies," "Dr. Just said. "Moreover, it points to new types of therapies that may help rehab the white matter in autism."
Co-authors of the study included Yanni Liu, PhD, and Timothy Keller, PhD, of CMU; Diane Williams, PhD, CCC-SLP, assistant professor of speech-language pathology at Duquesne University; and Nancy Minshew, MD, professor of psychiatry and neurology at University of Pittsburgh School of Medicine.
This research was funded by the National Institute of Child Health and Human Development and the Autism Speaks Foundation.