1. Crespi B, Stead P, Elliot M. {{Evolution in Health and Medicine Sackler Colloquium: Comparative genomics of autism and schizophrenia}}. {Proc Natl Acad Sci U S A};2009 (Dec 1)
We used data from studies of copy-number variants (CNVs), single-gene associations, growth-signaling pathways, and intermediate phenotypes associated with brain growth to evaluate four alternative hypotheses for the genomic and developmental relationships between autism and schizophrenia: (i) autism subsumed in schizophrenia, (ii) independence, (iii) diametric, and (iv) partial overlap. Data from CNVs provides statistical support for the hypothesis that autism and schizophrenia are associated with reciprocal variants, such that at four loci, deletions predispose to one disorder, whereas duplications predispose to the other. Data from single-gene studies are inconsistent with a hypothesis based on independence, in that autism and schizophrenia share associated genes more often than expected by chance. However, differentiation between the partial overlap and diametric hypotheses using these data is precluded by limited overlap in the specific genetic markers analyzed in both autism and schizophrenia. Evidence from the effects of risk variants on growth-signaling pathways shows that autism-spectrum conditions tend to be associated with up-regulation of pathways due to loss of function mutations in negative regulators, whereas schizophrenia is associated with reduced pathway activation. Finally, data from studies of head and brain size phenotypes indicate that autism is commonly associated with developmentally-enhanced brain growth, whereas schizophrenia is characterized, on average, by reduced brain growth. These convergent lines of evidence appear most compatible with the hypothesis that autism and schizophrenia represent diametric conditions with regard to their genomic underpinnings, neurodevelopmental bases, and phenotypic manifestations as reflecting under-development versus dysregulated over-development of the human social brain.
2. McCarthy J, Hemmings C, Kravariti E, Dworzynski K, Holt G, Bouras N, Tsakanikos E. {{Challenging behavior and co-morbid psychopathology in adults with intellectual disability and autism spectrum disorders}}. {Res Dev Disabil};2009 (Nov 30)
We investigated the relationship between challenging behavior and co-morbid psychopathology in adults with intellectual disability (ID) and autism spectrum disorders (ASDs) (N=124) as compared to adults with ID only (N=562). All participants were first time referrals to specialist mental health services and were living in community settings. Clinical diagnoses were based on ICD-10 criteria and presence of challenging behavior was assessed with the Disability Assessment Schedule (DAS-B). The analyses showed that ASD diagnosis was significantly associated with male gender, younger age and lower level of ID. Challenging behavior was about four times more likely in adults with ASD as compared to non-ASD adults. In those with challenging behavior, there were significant differences in co-morbid psychopathology between ASD and non-ASD adults. However, after controlling for level of ID, gender and age, there was no association between co-morbid psychopathology and presence of challenging behavior. Overall, the results suggest that presence of challenging behavior is independent from co-morbid psychopathology in adults with ID and ASD.
3. Nakano T, Ota H, Kato N, Kitazawa S. {{Deficit in visual temporal integration in autism spectrum disorders}}. {Proc Biol Sci};2009 (Dec 2)
Individuals with autism spectrum disorders (ASD) are superior in processing local features. Frith and Happe conceptualize this cognitive bias as ‘weak central coherence’, implying that a local enhancement derives from a weakness in integrating local elements into a coherent whole. The suggested deficit has been challenged, however, because individuals with ASD were not found to be inferior to normal controls in holistic perception. In these opposing studies, however, subjects were encouraged to ignore local features and attend to the whole. Therefore, no one has directly tested whether individuals with ASD are able to integrate local elements over time into a whole image. Here, we report a weakness of individuals with ASD in naming familiar objects moved behind a narrow slit, which was worsened by the absence of local salient features. The results indicate that individuals with ASD have a clear deficit in integrating local visual information over time into a global whole, providing direct evidence for the weak central coherence hypothesis.
4. Zalla T, Labruyere N, Clement A, Georgieff N. {{Predicting ensuing actions in children and adolescents with autism spectrum disorders}}. {Exp Brain Res};2009 (Dec 3)
This study investigated the ability to predict others’ action in a group of children and adolescents with autism spectrum disorders (ASD) (n = 18). Their performance was compared with a group of children with mental retardation (n = 13) and a group of children with typical development (n = 19). Participants were presented with short incomplete videotaped movies showing an actor executing familiar and non-familiar actions. When asked to predict the outcome, participants with ASD produced fewer correct responses and their performance did not improve for familiar actions, as compared to both comparison groups. In addition, they committed a greater number of errors of temporal inversion. These results provide new evidence that an impaired means-end analysis process, leading to a diminished sensitivity to the sequence structure of goal-directed actions, would disrupt the ability to understand and predict others’ actions. The comprehension of abnormalities in event knowledge provides a better insight of some of the problems that individuals with ASD encounter in spontaneously understanding real-life social situations.
