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Greta Vilidaite, Miaomiao Yu, Daniel Baker; Highly correlated internal noise across three perceptual and cognitive modalities. Journal of Vision 2016;16(12):809. doi: 10.1167/16.12.809.
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© ARVO (1962-2015); The Authors (2016-present)
Neural variability (noise) is an important limiting factor in neural processing widely observed in neurophysiological studies. Abnormal levels of neural noise have been implicated in some neurological disorders such as Autism. Noise in the early visual system can be measured using noise masking paradigms in which stimulus noise is used to inject external variability. However, previous research has not been able to compare this noise in other cognitive modalities. We used a 2AFC double-pass paradigm (Burgess & Colbourne, 1988, J Opt Soc Am A, 5: 617-627) in which stimulus intensity was jittered on a trial-by-trial basis for three discrimination tasks: a) grating contrast; b) facial expression intensity; and c) numerical summation (in which participants were asked which set of four numbers had the higher sum). The tasks were repeated twice with 200 trials/rep and consistency of responses between the passes was calculated. We tested 43 neurotypical observers and also obtained an estimate of autistic traits with the Autism Quotient (AQ). There were substantial significant positive correlations between consistency scores across all three modalities: faces and numbers (Spearman's ρ=.63, p< .0001), faces and contrast (ρ=.71, p< .0001) and numbers and contrast (ρ=.56, p< .0001). Furthermore, a Principal Components Analysis showed that all three consistency scores load onto a single factor, which explained 77% of the variance. Individual observers' factor loadings were also found to be significantly negatively correlated with AQ scores (ρ=-.39, p=.009, two-tailed), suggesting that those with more autistic traits had higher internal variability. Our results imply either a single source of late decision noise, common across all tasks, or a common factor of endogenous noise across the various brain regions involved in each task. Our finding of lower response consistency in people with higher levels of autistic traits supports current theories of increased internal noise in autism.
Meeting abstract presented at VSS 2016
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