title: Regional callosal morphology in autism and macrocephaly.
abstract: Previous investigations have reported decreased size of the corpus callosum (CC) in autism. However, little is known of the regional distribution of these callosal abnormalities. Additional uncertainty exists regarding the role of head size with respect to variations in callosal size in individuals with autism. This study investigated the size of the CC in 5 groups of high functioning individuals: (1) normocephalic autistic individuals; (2) autism with macrocephaly; (3) non-autistic normocephalic controls; (4) non-autistic participants with benign macrocephaly; and (5) a reading disordered (RD) group, comprised of non-autistic individuals with a deficit in reading. The CC was traced from midsaggital MRIs and the outlines partitioned into 99 equidistant width measures. Factor analysis of the 99 widths revealed 10 contiguous callosal regions. Individuals with macrocephaly (autistic and non-autistic) had larger total CC size. Regional analysis revealed a significantly larger CC midbody in macrocephaly, regardless of presence or absence of autism. Within normocephalic individuals, those with autism had a smaller CC genu and midbody than either non-autistic controls or RD individuals. These results underscore the importance of considering head size in studies of CC morphology in autism. These findings add to the literature implicating problems of interhemispheric connectivity being present in individuals with autism.
authors.affiliation: The Travis Research Institute, Fuller Graduate School of Psychology, Jerry L. Pettis Memorial VA Medical Center, Loma Linda, California, USA.
authors.forename: Shirley
authors.initials: S
authors.lastname: Kilian
authors.forename: Warren S
authors.initials: WS
authors.lastname: Brown
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Hallam
authors.forename: William
authors.initials: W
authors.lastname: McMahon
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Lu
authors.forename: Michael
authors.initials: M
authors.lastname: Johnson
authors.forename: Erin D
authors.initials: ED
authors.lastname: Bigler
authors.forename: Janet
authors.initials: J
authors.lastname: Lainhart
mesh_terms: D000293:Adolescent; D000328:Adult; D061085:Agenesis of Corpus Callosum; D001321:Autistic Disorder / Q000175:diagnosis* / Q000503:physiopathology; D001921:Brain / Q000002:abnormalities* / Q000473:pathology*; D002508:Cephalometry; D002648:Child; D003337:Corpus Callosum / Q000473:pathology*; D019465:Craniofacial Abnormalities / Q000175:diagnosis* / Q000503:physiopathology; D004410:Dyslexia / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests; D012016:Reference Values