title: Greater magnocellular saccadic suppression in high versus low autistic tendency suggests a causal path to local perceptual style.
abstract: Saccadic suppression-the reduction of visual sensitivity during rapid eye movements-has previously been proposed to reflect a specific suppression of the magnocellular visual system, with the initial neural site of that suppression at or prior to afferent visual information reaching striate cortex. Dysfunction in the magnocellular visual pathway has also been associated with perceptual and physiological anomalies in individuals with autism spectrum disorder or high autistic tendency, leading us to question whether saccadic suppression is altered in the broader autism phenotype. Here we show that individuals with high autistic tendency show greater saccadic suppression of low versus high spatial frequency gratings while those with low autistic tendency do not. In addition, those with high but not low autism spectrum quotient (AQ) demonstrated pre-cortical (35-45 ms) evoked potential differences (saccade versus fixation) to a large, low contrast, pseudo-randomly flashing bar. Both AQ groups showed similar differential visual evoked potential effects in later epochs (80-160 ms) at high contrast. Thus, the magnocellular theory of saccadic suppression appears untenable as a general description for the typically developing population. Our results also suggest that the bias towards local perceptual style reported in autism may be due to selective suppression of low spatial frequency information accompanying every saccadic eye movement.
authors.affiliation: Centre for Human Psychopharmacology Swinburne University of Technology Melbourne, Australia.
authors.forename: David P
authors.initials: DP
authors.lastname: Crewther
authors.affiliation: Centre for Human Psychopharmacology Swinburne University of Technology Melbourne, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Crewther
authors.affiliation: Centre for Human Psychopharmacology Swinburne University of Technology Melbourne, Australia.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bevan
authors.affiliation: Brain and Mind Institute, University of Western Ontario London, Ontario, Canada.
authors.forename: Melvyn A
authors.initials: MA
authors.lastname: Goodale
authors.affiliation: La Trobe University Melbourne, Australia.
authors.forename: Sheila G
authors.initials: SG
authors.lastname: Crewther
keywords: autistic tendency; magnocellular; nonlinear visual evoked potential; saccadic suppression