Developmental biology - Autism|
Amygdala Connections In Autistic Children Weaker
Communication between brain regions take unexpected twists and turns in autism...
Unique patterns of neural communications are found in brains of children with autism.
At a time different parts of the brain are supposed to be talking to each other or working together, the communication between different regions of the autistic brain appear to take unexpected exits and detours for no apparent reason.
Think of the brain as a complex transportation hub, a place where neural traffic heads off in any number of directions to make connections while processing something as simple as your mother's smile.
Now consider the same center in a child with an autism spectrum disorder (ASD). At a time different parts of the brain are supposed to be talking to each other or working together, this communication between different regions of the brain takes unexpected exits and detours for no apparent reason.
A team of San Diego State University (SDSU) researchers, studying MRI scans of school-age children's brains, found just such unique patterns of neural communication involving the amygdala, the area of the brain responsible for processing social information. In children with ASDs, amygdala connections with other parts of the brain proved to be weaker with some brain regions - but stronger with others - when compared to typically developing children of the same age.
A region of the brain showing marked differences connecting with the amygdala was the occipital cortex, located in the rear of the brain. It helps encode facial expressions, gaze and other facial cues, explains SDSU psychologist Inna Fishman, research leader.
These findings point to possible brain "markers" for autism spectrum disorders which further characterize autism in biological and not just behavioral terms. Fishman feels such markers could potentially become a tool to identify autism in children with the developmental disorder which can impair social communication and interaction.
"The patterns of amygdala connections are very unique in autism. What we found is not necessarily what I would have predicted. We measured connections from the amygdala to the entire brain. Findings in the visual cortex kind of surprised me."
Inna Fishman PhD, Brain Development Imaging Laboratories, Department of Psychology, San Diego State University, San Diego, California, USA.
Fishman, co-author Ralph-Axel Müller, along with colleagues contributing to the research, published their results in the Journal of the American Academy of Child & Adolescent Psychiatry.
Image Credit: Hindu Times.
Fishman is founding director of the SDSU Center for Autism, an interdisciplinary group of researchers and clinical scientists from multiple SDSU colleges and departments. Müller is director of SDSU's Brain Development Imaging Laboratories. Their work was supported by grants from the National Institutes of Health. Results were based on brain imaging from 55 children, aged 7 to 17, identified with ASDs and compared with 55 typically developing children of the same age.
The functional MRI used in the research measured how brain activity changes over time — in this case, a period of six minutes. It provides a picture of ongoing communication between different brain regions, known as "functional connectivity," showing how synchronized the amygdala's activity is with other brain areas. MRIs revealed weaker connections between the amygdala and the occipital cortex, Fishman added. In addition, the MRIs showed that the expected strengthening of connections between amygdala and the frontal cortex that takes place during adolescence in typically developing youth — was entirely absent in ASD participants.
This absence of a continuing brain maturation associated with typical adolescence may contribute to the social communication difficulties experienced by children with ASDs as they reach their teen years and young adulthood.
Fishman emphasizes there may be other forms of disrupted coordination between the amygdala and the brain. Although it isn't yet possible to say whether this causes any difference in social functioning seen in children with ASDs, this may partly be because of the age of children in this study.
"Having scanned kids who are 10, 12 or 14 years old, and having found differences at those ages, doesn't allow us to make inferences about what might have caused these differences," she points out. "At that point, connections in the brain are formed and already quite established."
As a follow-up, Fishman is studying brain connectivity and organization in ASDs toddlers and preschoolers, when autism symptoms first manifest. She hopes to learn whether early behaviors seen in children with ASDs lead to the atypical connection patterns, or the other way around.
Fishman hopes an overall, understanding of the biology behind ASDs "brings us incrementally closer" to improved clinical decisions concerning diagnosis or prognosis of ASDs. Earlier prognosis possibly leading to a more tailored intervention focusing on specific brain circuits and/or unique brain connections identified.
Converging evidence indicates that brain abnormalities in autism spectrum disorders (ASDs) involve atypical network connectivity. Given the central role of social deficits in the ASD phenotype, this investigation examined functional connectivity of the amygdala—a brain structure critically involved in processing of social information—in children and adolescents with ASDs, as well as age-dependent changes and links with clinical symptoms.
Resting-state functional magnetic resonance imaging (rs-fMRI) data from 55 participants with ASDs and 50 typically developing (TD) controls, aged 7 to 17 years, were included. Groups were matched for age, gender, IQ, and head motion. Functional connectivity MRI (fcMRI) analysis was applied to examine intrinsic functional connectivity (iFC) of the amygdala, including cross-sectional tests of age-related changes.
Direct between-group comparisons revealed reduced functional connectivity between bilateral amygdalae and left inferior occipital cortex, accompanied by greater connectivity between right amygdala and right sensorimotor cortex in the ASD group. This atypical pattern of amygdala connectivity was associated with decreased symptom severity and better overall functioning, as specifically seen in an ASD subgroup with the most atypical amygdala iFC but the least impaired social functioning. Age-related strengthening of amygdala-prefrontal connectivity, as observed in the TD group, was not detected in children with ASDs.
Findings support aberrant network sculpting in ASDs, specifically atypical integration between amygdala and primary sensorimotor circuits. Paradoxical links between atypical iFC and behavioral measures suggest that abnormal amygdala functional connections may be compensatory in some individuals with ASDs.
Inna Fishman PhD, Annika C. Linke PhD, Janice Hau PhD, Ruth A. Carper PhD, Ralph-Axel Müller PhD.
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Strengthening of amygdala-prefrontal connectivity, seen in typically developing (TD) teens, is not detected in children with ASDs. Credit: Brain Facts For Kids