title: Abnormal magnocellular pathway visual processing in infants at risk for autism.
abstract: BACKGROUND
  A wealth of data has documented impairments in face processing in individuals with autism spectrum disorders (ASD). Recently, the suggestion has been made that these impairments may arise from abnormal development of a subcortical system involved in face processing that originates in the magnocellular pathway of the primate visual system.
  
  
  METHODS
  To test this developmental hypothesis, we obtained visual perceptual data from 6-month-old infants who were at risk for ASD because they had an older sibling diagnosed with the disorder ("high-risk infants"). To measure sensitivity of the magnocellular (M) pathway and, for comparison, of the parvocellular (P) visual pathway, we employed visual stimuli designed to selectively stimulate the two. Sensitivity data from high-risk infants (n = 13) were compared with data from matched control infants (i.e., "low-risk" infants with no family history of ASD, n = 26).
  
  
  RESULTS
  On the P pathway stimulus, high-risk infants exhibited sensitivities that were identical to those of control infants. By contrast, on the M pathway stimulus, high-risk infants exhibited sensitivities nearly twofold greater than those of control infants.
  
  
  CONCLUSIONS
  Given that ASD and its symptoms are known to run in families, these preliminary results suggest that ASD may be associated with abnormal M pathway function early in infancy, which may aid in early diagnosis of the disorder.
authors.affiliation: Department of Psychology, University of California, San Diego, La Jolla, California 92093, USA.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: McCleery
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Allman
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Carver
authors.forename: Karen R
authors.initials: KR
authors.lastname: Dobkins
mesh_terms: D000377:Agnosia; D000704:Analysis of Variance; D001321:Autistic Disorder / Q000175:diagnosis* / Q000503:physiopathology*; D002675:Child, Preschool; D003118:Color Perception / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology; D002658:Developmental Disabilities; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009483:Neuropsychological Tests; D010775:Photic Stimulation / Q000379:methods; D011446:Prospective Studies; D012306:Risk; D014795:Visual Pathways / Q000503:physiopathology*