While in the past autism research has often been dedicated to a single core deficit or localized brain defect, growing evidence suggests that autism is a "distributed disorder" involving many genes and neuroanatomical loci, and many neurofunctional and behavioral systems. The resulting need for studies of network organization and brain connectivity is hampered by our lack of (i) a precise understanding of what impaired functional connectivity ("underconnectivity") in autism means, and (ii) a model integrating evidence of abnormal local cortical architecture with evidence of "underconnectivity". Children with autism (ages 13-17 years) and matched typically developing children will participate in neuropsychological testing, diffusion tensor imaging (DTI), and functional MRI (fMRI) experiments during performance on two simple sensory tasks (visual, auditory) and a more complex lexico-semantic language task. Event-related fMRI designs will allow us to identify activation peaks in primary visual and auditory cortices, primary motor cortex, and left inferior frontal cortex. These activation peaks will be further used for functional connectivity (fcMRI) analyses, testing for time series correlations across the brain. According to our overarching hypothesis, reduced activation concordance (reflecting compromised local cortical organization) will be associated with reduced interregional connectivity (functional, anatomical), reduced white matter integrity, and with impaired neuropsychological performance in autism.
Four specific aims will test hypotheses for the autism group of (i) reduced concordance of activity in core activation sites (fMRI), (ii) correlation between functional connectivity (fcMRI) and activation concordance, (iii) correlations of anatomical connectivity and white matter integrity (DTI) with local activation concordance and functional connectivity, and (iv) correlations between imaging (concordance, connectivity) and neuropsychological measures. Establishing links between cognitive-behavioral impairment, local cortical compromise, functional connectivity, and anatomical connectivity will have translational relevance in at least two respects. First, it promises to unite several currently separate lines of neurodevelopmental research in autism that may be the foundation for therapeutic advances;and second, it will provide an approach to characterizing neurofunctionally defined endophenotypes of autism, in support of identifying subtypes of genetic risk within the population.
Narrative Autism is a pediatric health issue of growing urgency. Genetic approaches require the identification of biologically defined subtypes (endophenotypes), to which this project will contribute by examining links between local cortical organization, brain connectivity, and cognition in children with autism, using several types of magnetic resonance imaging.
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