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Monozygotic twins with Asperger syndrome: differences in behaviour reflect variations in brain structure and
Matthew K Belmonte1, Ruth A Carper
1Autism Research Centre, Department of Psychiatry, University of Cambridge, UK. belmonte@mit.edu
Brain and Cognition
|February 7, 2006
Summary
This study examined monozygotic twins with differing Asperger syndrome symptoms. Brain structure and function differences in the lower-functioning twin correlated with behavioral and cognitive variations, highlighting autism
Area of Science:
- Neuroscience
- Psychiatry
- Genetics
Background:
- Monozygotic twins offer a unique model to study genetic versus environmental influences on neurodevelopmental disorders.
- Asperger syndrome, now part of Autism Spectrum Disorder (ASD), presents with social-communication challenges and restricted interests.
- Understanding the neurobiological underpinnings of discordance in ASD within genetically identical twins is crucial for targeted interventions.
Purpose of the Study:
- To investigate the neuroanatomical and functional brain differences between monozygotic twins discordant for Asperger syndrome symptoms.
- To correlate observed brain structure and function with behavioral and cognitive profiles in each twin.
- To explore the relationship between brain morphology and neural activation patterns in the context of ASD.
Main Methods:
- Psychometric assessments to evaluate cognitive and behavioral phenotypes.
- Morphometric analysis to compare brain volumes and proportions.
- Functional magnetic resonance imaging (fMRI) to assess neural activation during a visual attention task.
Main Results:
- The lower-functioning twin exhibited overall smaller brain volume, reduced right cerebellum size, and a disproportionately enlarged left frontal lobe.
- This twin showed minimal differential brain activation between high and low-congruence distractors during the visual task.
- The higher-functioning twin displayed typical autistic patterns of brain activation (anterior deactivation, posterior hyperactivation) with superimposed normal superior frontal cortex activity.
Conclusions:
- Morphometric findings align with known brain-behavior correlations in autism spectrum disorder.
- Functional imaging results suggest a link between structural brain differences and altered neural processing in Asperger syndrome.
- This case highlights how genetic identity does not preclude significant neurodevelopmental divergence in ASD, impacting both brain structure and function.