title: Abnormalities in brain systems supporting individuation and enumeration in autism.
abstract: Previous work indicates that adults with autism display a decreased capacity when rapidly enumerating small sets of elements (i.e., subitizing), compared to typically developing (TD) individuals. This ability is crucial for fundamental visual functions such as object individuation and parallel processing. Thus, the deficit in autism suggests limits in these skills. To examine the neural basis of this limitation, adults with and without high functioning autism rapidly enumerated 1 to 8 randomly located squares during a neuroimaging study. Typically, adults are thought to use parallel visual processes to quantify up to three or four elements, and serial processes to enumerate more (5+) elements. We hypothesized that parietal lobe regions associated with counting would be recruited with smaller sets of elements in adults with autism, compared to TD adults. Consistent with this hypothesis, activation in parietal regions increased with smaller set sizes in adults with autism compared to TD adults. Increased activation for three elements was evident in several regions, including those thought to underlie subitizing. In addition, regions specific to the counting range in TD adults were often equally active for set sizes in the subitizing range in the adults with autism. Finally, significant deactivation was evident in TD adults, presumably reflecting relative suppression of regions specialized for competing processes, but was not apparent in adults with autism. These differences in brain function in adults with autism on a simple enumeration task suggest atypical brain organization and function that is likely to impact most visual tasks, especially those with multiple elements.
authors.affiliation: Department of Psychiatry, University of Pittsburgh.
authors.forename: Kirsten
authors.initials: K
authors.lastname: O'Hearn
authors.affiliation: Department of Psychiatry, University of Pittsburgh.
authors.forename: Katerina
authors.initials: K
authors.lastname: Velanova
authors.affiliation: Department of Psychiatry, University of Pittsburgh.
authors.forename: Andrew
authors.initials: A
authors.lastname: Lynn
authors.affiliation: Department of Psychiatry, University of Pittsburgh.
authors.forename: Catherine
authors.initials: C
authors.lastname: Wright
authors.affiliation: Department of Psychiatry, University of Pittsburgh.
authors.forename: Michael
authors.initials: M
authors.lastname: Hallquist
authors.affiliation: Department of Psychiatry, University of Pittsburgh.|Department of Neurology, University of Pittsburgh.
authors.forename: Nancy
authors.initials: N
authors.lastname: Minshew
authors.affiliation: Department of Psychiatry, University of Pittsburgh.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Luna
mesh_terms: D000328:Adult; D001321:Autistic Disorder / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods; D005260:Female; D006801:Humans; D007207:Individuation; D008279:Magnetic Resonance Imaging; D008297:Male; D008433:Mathematics; D010296:Parietal Lobe / Q000503:physiopathology; D010364:Pattern Recognition, Visual; D011930:Reaction Time; D055815:Young Adult
keywords: autism spectrum disorder; counting; fMRI; number; parietal; subitizing