Posts tagged autism
Articles and news from the latest research reports.
Autism Risk Gene Linked to Differences in Brain Structure
ScienceDaily (Mar. 21, 2012) — Healthy individuals who carry a gene variation linked to an increased risk of autism have structural differences in their brains that may help explain how the gene affects brain function and increases vulnerability for autism. The results of this innovative brain imaging study are described in an article in the groundbreaking neuroscience journal Brain Connectivity, a bimonthly peer-reviewed publication from Mary Ann Liebert, Inc. The article is available free online at the Brain Connectivity website.
"This is one of the first papers demonstrating a linkage between a particular gene variant and changes in brain structure and connectivity in carriers of that gene," says Christopher Pawela, PhD, Co-Editor-in-Chief and Assistant Professor, Medical College of Wisconsin. "This work could lead to the creation of an exciting new line of research investigating the impact of genetics on communication between brain regions."
Although carriers of the common gene variant CNTNAP2 — identified as an autism risk gene — may not develop autism, there is evidence of differences in brain structure that may affect connections and signaling between brain regions. These disruptions in brain connectivity can give rise to functional abnormalities characteristic of neuropsychological disorders such as autism.
Emily Larson Dennis, Neda Jahanshad, Jeffrey D Rudie, Jesse A Brown, Kori Johnson, Katie McMahon, Greig de Zubicaray, Grant Montgomery, Nicholas Martin, Margaret Wright, Susan Bookheimer, Mirella Dapretto, Arthur Toga, Paul Thompson. Altered Structural Brain Connectivity in Healthy Carriers of the Autism Risk Gene, CNTNAP2. Brain Connectivity, 2012; 120229030236004 DOI: 10.1089/brain.2011.0064
Source: Science Daily
New brain imaging and computer modeling predicts autistic brain activity and behavior
March 6, 2012
Schematic diagrams of a normal brain (left) and an autistic brain (right) highlight the white matter alterations in autism. Credit: Carnegie Mellon University
New research from Carnegie Mellon University’s Marcel Just provides an explanation for some of autism’s mysteries — from social and communication disorders to restricted interests — and gives scientists clear targets for developing intervention and treatment therapies.
Autism has long been a scientific enigma, mainly due to its diverse and seemingly unrelated symptoms until now.
Published in the journal Neuroscience and Biobehavioral Reviews, Just and his team used brain imaging and computer modeling to show how the brain’s white matter tracts — the cabling that connects separated brain areas — are altered in autism and how these alterations can affect brain function and behavior. The deficiencies affect the tracts’ bandwidth — the speed and rate at which information can travel along the pathways.
"White matter is the unsung hero of the human brain," said Just, the D.O. Hebb Professor of Psychology within CMU’s Dietrich College of Humanities and Social Sciences and director of the university’s Center for Cognitive Brain Imaging. "In autistic individuals, we can measure the quality of the white matter, and our computer model can predict how coordinated their brain activity will be. This gives us a precise account of the underlying alterations affecting autistic thought."
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Holding a Mirror to Brain Changes in Autism
ScienceDaily (Mar. 2, 2012) — Impaired social function is a cardinal symptom of autism spectrum disorders (ASDs). One of the brain circuits that enable us to relate to other people is the “mirror neuron” system. This brain circuit is activated when we watch other people, and allows our brains to represent the actions of others, influencing our ability to learn new tasks and to understand the intentions and experiences of other people.
This mirror neuron system is impaired in individuals with ASD and better understanding the neurobiology of this system could help in the development of new treatments.
In their new study, Dr. Peter Enticott at Monash University and his colleagues used transcranial magnetic stimulation to stimulate the brains of individuals with ASD and healthy individuals while they observed different hand gestures. This allowed the researchers to measure the activity of each individual’s mirror neuron system with millisecond precision in response to each observed action.
They found that the individuals with ASD showed a blunted brain response to stimulation of the motor cortex when viewing a transitive hand gesture. In other words, the mirror neuron system in the ASD individuals became less activated when watching the gestures, compared to the healthy group. In addition, among people with ASD, less mirror neuron activity was associated with greater social impairments. This finding adds to the evidence that deficits in mirror neuron system functioning contribute to the social deficits in ASD.
This finding also directly links a specific type of brain dysfunction in people with autism spectrum disorder to a specific symptom. This is important because “we do not have a substantial understanding of the brain basis of autism spectrum disorder, or a validated biomedical treatment for the disorder,” said Dr. Enticott. “If we can develop a substantial understanding of the biology of specific symptoms, this will allow us to develop treatments targeted specifically to the symptoms.”
"This study is an example of the effort to break down the component problems associated with autism spectrum disorder and to map these problems on to particular brain circuits," commented Dr. John Krystal, editor of Biological Psychiatry.
Enticott added, “We are currently investigating whether non-invasive brain stimulation can be used to improve mirror neuron activity in autism spectrum disorder, which would have substantial potential therapeutic implications.”
Source: Science Daily
This is an image of white matter pathways extracted from diffusion tensor imaging data for infants at-risk for autism. Warmer colors represent higher fractional anisotropy. Credit: Image created by Jason Wolff, Ph.D.
A new study led by the University of North Carolina at Chapel Hill found significant differences in brain development starting at age 6 months in high-risk infants who later develop autism, compared to high-risk infants who did not develop autism.
"It’s a promising finding," said Jason J. Wolff, PhD, lead author of the study and a postdoctoral fellow at UNC’s Carolina Institute for Developmental Disabilities (CIDD). "At this point, it’s a preliminary albeit great first step towards thinking about developing a biomarker for risk in advance of our current ability to diagnose autism."
The study also suggests, Wolff said, that autism does not appear suddenly in young children, but instead develops over time during infancy. This raises the possibility “that we may be able to interrupt that process with targeted intervention,” he said.
Joseph Piven, MD, director of the CIDD, is senior author of the study.
The study was published online on Friday, Feb. 17 at AJP in Advance, a section of the website of the American Journal of Psychiatry. Its results are the latest from the ongoing Infant Brain Imaging Study (IBIS) Network, which is funded by the National Institutes of Health and headquartered at UNC. Piven received an NIH Autism Centers of Excellence (ACE) program network award for the IBIS Network in 2007. ACE networks consist of researchers at many facilities in locations throughout the country, all of whom work together on a single research question.
Participants in the study were 92 infants who all have older siblings with autism and thus are considered to be at high risk for autism themselves. All had diffusion tensor imaging – which is a type of magnetic resonance imaging (MRI) – at 6 months and behavioral assessments at 24 months. Most also had additional brain imaging scans at either or both 12 and 24 months.
At 24 months, 28 infants (30 percent) met criteria for autism spectrum disorders while 64 infants (70 percent) did not. The two groups differed in white matter fiber tract development – pathways that connect brain regions – as measured by fractional anisotropy (FA). FA measures white matter organization and development, based on the movement of water molecules through brain tissue.
This study examined 15 separate fiber tracts, and found significant differences in FA trajectories in 12 of the 15 tracts between infants who did develop autism versus infants who did not. Infants who later developed autism had elevated FA at six months but then experienced slower change over time. By 24 months of age, infants with autism had lower FA values than infants without autism.
"This evidence, which implicates multiple fiber pathways, suggests that autism is a whole-brain phenomenon not isolated to any particular brain region," Wolff said.
Provided by University of North Carolina School of Medicine
Source: medicalxpress