Stanford/Packard autism researchers seek twins for brain-imaging study
Posted Feb 02 2010 12:42pm
The subject of twins and autism concordance comes up on LeftBrainRightBrain periodically. I find the questions raised to be very interesting and I’ve said a number of times I hope people take a closer look at twins.
Enter Dr. Antonio Hardan of the Lucile Packard Children’s Hospital (LPCH) at Stanford University in California. Dr. Hardan is a Child Psychiatrist with much experience in exploring brain structure in autistics. Yesterday there was a press release (which I can’t find now) calling for subjects for a twin study. The announcement is on the LPCH website.
Stanford/Packard autism researchers seek twins for brain-imaging study
“We’re doing a twin study to try to sort the impact of genetics on brain abnormalities in autism from the impact of the environment,” said lead scientist Antonio Hardan, MD, who is a child psychiatrist at Lucile Packard Children’s Hospital and associate professor of psychiatry and behavioral sciences at Stanford. Hardan’s team will use magnetic resonance imaging to scan the brains of 120 pairs of twins, some with autism and some without, to look for gene-brain associations.
Previous research has indicated about 75 to 80 percent of autism is explained by genetics, Hardan said. This means that if one member of a pair of identical twins has autism, the other will usually be affected. Having a fraternal (non-identical) twin or other sibling with autism raises a child’s likelihood of an autism diagnosis, but not as much.
Still, no one knows the degree to which genetic factors explain distinct structural and chemical characteristics in the brains of autistic individuals, which may include differences in total brain size and in the corpus callosum and amygdala.
Hardan’s research team will compare the level of similarity in brain structures of identical twins, who share all their genes, with the brain similarities of fraternal twins, who share half of their genes. They will also compare pairs of twins with autism with typically developing (non-autistic) twins to gain insight into which developmental patterns are distinct to autism. They then hope to figure out whether and to what degree there is a correlation between genetic profiles and the brain metabolites and structures of people with autism.
The team is seeking same-sex twin pairs aged 3 to 14. Study subjects can be identical or non-identical twins. The scientists plan to scan 80 pairs in which one or both twins have autism, and 40 typically developing pairs in which neither twin has autism. The scanning method, MRI, is non-invasive and does not involve any radiation exposure. All subjects will also receive standard cognitive and IQ assessments, as well as a battery of diagnostic tests for autism.
Testing will take four to five hours over two consecutive days, and each twin who completes the testing will be compensated $100. Subjects will receive summaries of their cognitive testing results, and confirmation of whether they are identical or fraternal twins. The twins’ families will also be compensated for travel expenses to and from Stanford.
“The scientific value of the study is a major one,” Hardan concluded. “We don’t know how much is inherited in terms of specific brain abnormalities in autism, and we also need to learn more about how environmental factors play into the development of the autistic brain. This study will help us gain that understanding.”
Department of Psychiatry and Behavioral Sciences, State University of New York at Upstate Medical University, Syracuse, New York 13210, USA. firstname.lastname@example.org
In order to disentangle genetic and environmental contributions to cortical anomalies in children with autism, we investigated cortical folding patterns in a cohort of 14 monozygotic (MZ) twin pairs who displayed a range of phenotypic discordance for autism, and 14 typically developing community controls. Cortical folding was assessed with the gyrification index, which was calculated on high resolution anatomic MR images. We found that the cortical folding patterns across most lobar regions of the cerebral cortex was highly discordant within MZ twin pairs. In addition, children with autism and their co-twins exhibited increased cortical folding in the right parietal lobe, relative to age- and gender-matched typical developing children. Increased folding in the right parietal lobe was associated with more symptoms of autism for co-twins. Finally, the robust association between cortical folding and IQ observed in typical children was not observed in either children with autism or their co-twins. These findings, which contribute to our understanding of the limits of genetic liability in autism, suggest that anomalies in the structural integrity of the cortex in this PDD may disrupt the association between cortical folding and intelligence that has been reported in typical individuals, and may account, in part, for the deficits in visual spatial attention and in social cognition that have been reported in children with autism.
I find this to be rather interesting. “We found that the cortical folding patterns across most lobar regions of the cerebral cortex was highly discordant within MZ twin pairs.” In other words, the physical brain structure is different within “identical” twin pairs. Recall the twin pairs in this study “displayed a range of phenotypic discordance for autism”. It is hard for me to simplify that without oversimplification, but the twins do not have the same autistic traits, and perhaps differing ASD diagnoses.
Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA. email@example.com
The gyrification index (GI), the ratio of total to outer cortical contour, was applied to measure the cerebral folding patterns in autism. GI was examined on a frontal coronal slice obtained from MRI scans of 30 nonmentally retarded individuals with autism and 32 matched healthy controls. In the autistic group, left frontal GI was higher in children and adolescents but not in adults. Cortical folding was decreased bilaterally with age in the total autistic sample but not in controls. These preliminary findings suggest that the gyrification patterns in autism may be abnormal, which could be related to the various cortical anomalies observed in this disorder.
Below is an image from the Hardan study. The “gyrification ratio” is a measure of the inner contour to the outer contour.
The results of the Hardan study were “preliminary”, and there was a statistically significant difference observed in those measurements. What was observed was “Interestingly, there was a significant decrease in the frontal gyrification patterns with age in the autistic group (right side: r=?0.44, P=0.012; left side: r=?0.48, P=0.006), which was not seen in controls (right side: r=?0.12, P=0.51; left side: r=?0.065, P=0.72). ”
I find this interesting—the GI (consider it the “folding” in the brain) differs by age for the autistics but not for the controls.
Again, I find the proposed twin study to be interesting and potentially very valuable. I hope Dr. Hardan can find enough study subjects to complete the study. There probably are not a lot of parents of autistic twins who live near Stanford reading this blog, but who knows?
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