title: Neurophysiological hyperresponsivity to sensory input in autism spectrum disorders.
abstract: BACKGROUND
  Atypical sensory processing is a common clinical observation in autism spectrum disorder (ASD). Neural hyperexcitability has been suggested as the cause for sensory hypersensitivity, a frequently reported clinical observation in ASD. We examined visual evoked responses to parametric increases in stimulus contrast in order to model neural responsivity of sensory systems in ASD.
  
  
  METHODS
  Thirteen high-functioning individuals with ASD and 12 typically developing (TD) individuals completed a steady-state visual evoked potential study. Stimuli were vertical circular gratings oscillating at 3.76 Hz at varying contrasts (5, 10, 20,…, 90 % contrast, 10 levels). The average spectral power at the stimulus oscillation frequency was calculated for each contrast level.
  
  
  RESULTS
  The magnitude of evoked sensory responses increased at a significantly greater rate and resulted in disproportionately elevated activation with higher contrasts in the ASD group. Approximately 45 % of ASD participants had rates of response increases greater than any TD participant. This alteration was highly associated with parental reports of these participants' sensory difficulties.
  
  
  CONCLUSIONS
  Greater increases in visual responses over contrast manipulation suggest heightened excitability in the sensory cortex in ASD participants. Heightened neural excitability was observed in a substantial portion but not all of the ASD participants. This pattern suggests that individuals with higher excitability may constitute a neurobiologically distinct subgroup requiring individualized treatment interventions.
authors: Center for Autism and Developmental Disabilities, Department of Psychiatry, University of Texas Southwestern, 5323 Harry Hines Blvd., Dallas, TX 75390 USA.
authors: Yukari
authors: Y
authors: Takarae
authors: Center for Autism and Developmental Disabilities, Department of Psychiatry, University of Texas Southwestern, 5323 Harry Hines Blvd., Dallas, TX 75390 USA.
authors: Savanna R
authors: SR
authors: Sablich
authors: Center for Autism and Developmental Disabilities, Department of Psychiatry, University of Texas Southwestern, 5323 Harry Hines Blvd., Dallas, TX 75390 USA.
authors: Stormi P
authors: SP
authors: White
authors: Center for Autism and Developmental Disabilities, Department of Psychiatry, University of Texas Southwestern, 5323 Harry Hines Blvd., Dallas, TX 75390 USA.
authors: John A
authors: JA
authors: Sweeney
keywords: Autism; Contrast sensitivity; Heterogeneity; Individual differences; Sensory hypersensitivity