The anatomy of the callosal and visual-association pathways in high-functioning autism: a DTI tractography study.
There is increasing recognition that many of the core behavioral impairments that characterize autism potentially emerge from poor neural synchronization across nodes comprising dispersed cortical networks. A likely candidate for the source of this atypical functional connectivity in autism is an alteration in the structural integrity of intra- and inter-hemispheric white matter (WM) tracts that form large-scale cortical networks. To test this hypothesis, in a group of adults with high-functioning autism (HFA) and matched control participants, we used diffusion tensor tractography to compare the structural integrity of three intra-hemispheric visual-association WM tracts, the inferior longitudinal fasciculus (ILF), the inferior fronto-occipito fasciculus (IFOF) and the uncinate fasciculus (UF), with the integrity of three sub-portions of the major inter-hemispheric fiber tract, the corpus callosum. Compared with the control group, the HFA group evinced an increase in the volume of the intra-hemispheric fibers, particularly in the left hemisphere, and a reduction in the volume of the forceps minor (F-Mi) and body of the corpus callosum. The reduction in the volume of the F-Mi also correlated with an increase in repetitive and stereotypical behavior as measured by the Autism Diagnostic Interview. These findings suggest that the abnormalities in the integrity of key inter- and intra-hemispheric WM tracts may underlie the atypical information processing observed in these individuals.
Thomas
Cibu
C
Department of Psychology, Carnegie Mellon University, PA 15213, USA. thomascp@mail.nih.gov
Humphreys
Kate
K
Jung
Kwan-Jin
KJ
Minshew
Nancy
N
Behrmann
Marlene
M
D000328:Adult; D001321:Autistic Disorder / Q000473:pathology*; D001921:Brain / Q000473:pathology; D003337:Corpus Callosum / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009415:Nerve Net / Q000473:pathology; D014795:Visual Pathways / Q000473:pathology*