title: Behavioral evidence for a functional link between low- and mid-level visual perception in the autism spectrum.
abstract: BACKGROUND
  Most investigations of visuo-perceptual abilities in the Autism Spectrum (AS) are level-specific, using tasks that selectively solicit either lower- (i.e., spatial frequency sensitivity), mid- (i.e., pattern discrimination) or higher-level processes (i.e., face identification) along the visual hierarchy. Less is known about how alterations at one level of processing (i.e., low-level) interact with that of another (i.e., mid-level). The aim of this study was to assess whether manipulating the physical properties (luminance vs texture) of local contour elements of a mid-level, visual pattern interferes with the discrimination of that pattern in a differential manner for individuals with AS.
  
  
  METHODS
  Twenty-nine AS individuals and thirty control participants (range 14-27 years) were asked to discriminate between perfect circles and Radial Frequency Patterns (RFP) of two, three, five, and 10 radial frequencies (RF), or deformations along the pattern's contour. When RFP have few deformations (<five RF), a global, pattern analysis is needed for shape discrimination. Conversely, when RFP contain many deformations (≥10 RF), discrimination is dependent on the analysis of local deformations along the RFP contour. The effect of manipulating RF on RFP discrimination was assessed for RFP whose local contour elements were defined by either luminance or texture information, the latter previously found less efficiently processed in AS individuals.
  
  
  RESULTS
  Two separate mixed factorial ANOVAs [2 (Group)×4 (RF)] were conducted on mean deformation thresholds for luminance- and texture-defined conditions. A significant Group×RF interaction was found for the luminance-defined condition where thresholds were higher in the AS group for the two and three RF conditions; no between-group differences were found for the five and 10 RF conditions. A significant main effect of group was identified for the texture-defined condition, where mean thresholds were higher for the AS group across all RF conditions assessed (two, three, five and 10); a Group×RF interaction effect was not found. Performance for each RFP condition was not affected across group by either chronological age or intelligence, as measured by either Weschler scales or Raven Progressive Matrices.
  
  
  CONCLUSIONS
  The ability of AS individuals to discriminate a circular pattern is differentially affected by the availability (number of deformations along the RFP contour) and type (luminance vs texture) of local, low-level elements defining its contour. Performance is unaffected in AS when RFP discrimination is dependent on the analysis of local deformations of luminance-defined contour elements, but decreased across all RF conditions when local contour elements are texture-defined. These results suggest that efficient pattern perception in AS is functionally related to the efficacy with which its local elements are processed, indicative of an early origin for altered mid-level, pattern perception in AS.
authors.affiliation: Perceptual Neuroscience Lab for Autism and Development (PNLab), Rivière-des-Prairies Hospital, Montreal, Canada; Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Department of Psychology, Université de Montréal, Montreal, Canada. Electronic address: perreault.audrey@gmail.com.
authors.forename: Audrey
authors.initials: A
authors.lastname: Perreault
authors.affiliation: Educational Neuroscience Research Centre, Health and Special Education, Emirates College for Advanced Education, Abu Dhabi, UAE. Electronic address: claudine.habak@ecae.ac.ae.
authors.forename: Claudine
authors.initials: C
authors.lastname: Habak
authors.affiliation: Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Department of Psychology, Université de Montréal, Montreal, Canada. Electronic address: franco.lepore@umontreal.ca.
authors.forename: Franco
authors.initials: F
authors.lastname: Lepore
authors.affiliation: Centre d'excellence en Troubles envahissants du développement de l'Université de Montréal (CETEDUM), Hôpital Rivière-des-Prairies, Canada. Electronic address: laurent.mottron@gmail.com.
authors.forename: Laurent
authors.initials: L
authors.lastname: Mottron
authors.affiliation: Centre d'excellence en Troubles envahissants du développement de l'Université de Montréal (CETEDUM), Hôpital Rivière-des-Prairies, Canada; Perceptual Neuroscience Lab for Autism and Development (PNLab), Canada; Department of Education and Counselling Psychology, McGill University, Montreal, Canada. Electronic address: armando.bertone@mcgill.ca.
authors.forename: Armando
authors.initials: A
authors.lastname: Bertone
mesh_terms: D000293:Adolescent; D000328:Adult; D001321:Autistic Disorder / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D010775:Photic Stimulation; D011581:Psychological Tests; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Autism Spectrum; Intermediate level vision; Low-level vision; Visuo-spatial perception