title: Diffusion Tensor Imaging Provides Evidence of Possible Axonal Overconnectivity in Frontal Lobes in Autism Spectrum Disorder Toddlers.
abstract: BACKGROUND
  Theories of brain abnormality in autism spectrum disorder (ASD) have focused on underconnectivity as an explanation for social, language, and behavioral deficits but are based mainly on studies of older autistic children and adults.
  
  
  METHODS
  In 94 ASD and typical toddlers ages 1 to 4 years, we examined the microstructure (indexed by fractional anisotropy) and volume of axon pathways using in vivo diffusion tensor imaging of fronto-frontal, fronto-temporal, fronto-striatal, and fronto-amygdala axon pathways, as well as posterior contrast tracts. Differences between ASD and typical toddlers in the nature of the relationship of age to these measures were tested.
  
  
  RESULTS
  Frontal tracts in ASD toddlers displayed abnormal age-related changes with greater fractional anisotropy and volume than normal at younger ages but an overall slower than typical apparent rate of continued development across the span of years. Posterior cortical contrast tracts had few significant abnormalities.
  
  
  CONCLUSIONS
  Frontal fiber tracts displayed deviant early development and age-related changes that could underlie impaired brain functioning and impact social and communication behaviors in ASD.
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla.
authors: Stephanie
authors: S
authors: Solso
authors: Clinical and Translational Research Institute, School of Medicine, University of California San Diego, La Jolla.
authors: Ronghui
authors: R
authors: Xu
authors: Clinical and Translational Research Institute, School of Medicine, University of California San Diego, La Jolla.
authors: James
authors: J
authors: Proudfoot
authors: Department of Radiology, Multimodal Imaging Laboratory, School of Medicine, University of California San Diego, La Jolla.
authors: Donald J
authors: DJ
authors: Hagler
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla.
authors: Kathleen
authors: K
authors: Campbell
authors: Department of Radiology, Multimodal Imaging Laboratory, School of Medicine, University of California San Diego, La Jolla.
authors: Vijay
authors: V
authors: Venkatraman
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla.
authors: Cynthia
authors: C
authors: Carter Barnes
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla.
authors: Clelia
authors: C
authors: Ahrens-Barbeau
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla.
authors: Karen
authors: K
authors: Pierce
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla.
authors: Anders
authors: A
authors: Dale
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla; Department of Psychiatry, School of Medicine, University of California San Diego, La Jolla; Desert-Pacific Mental Illness Research, Education and Clinical Center, Veterans Affairs San Diego Healthcare System, San Diego, California.
authors: Lisa
authors: L
authors: Eyler
authors: Department of Neuroscience, School of Medicine, University of California San Diego, La Jolla. Electronic address: ecourchesne@ucsd.edu.
authors: Eric
authors: E
authors: Courchesne
mesh_terms: D016880:Anisotropy; D000067877:Autism Spectrum Disorder / Q000000981:diagnostic imaging* / Q000473:pathology; D001369:Axons / Q000473:pathology; D002675:Child, Preschool; D003337:Corpus Callosum / Q000000981:diagnostic imaging / Q000254:growth & development / Q000473:pathology; D056324:Diffusion Tensor Imaging; D005260:Female; D005625:Frontal Lobe / Q000000981:diagnostic imaging* / Q000254:growth & development / Q000473:pathology; D006801:Humans; D007223:Infant; D008297:Male; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000254:growth & development / Q000473:pathology; D009929:Organ Size; D012720:Severity of Illness Index
keywords: Autism; DTI; Development; Frontal tracts; Tract FA; Tract volume