Luminance- and Texture-Defined Visual Perceptual Processing in Children and Adolescents with Asd; Comparison with Other Neurodevelopmental Conditions

Background: Individuals with Autism Spectrum Disorder (ASD) possess unique capacities related to visual perception (Mottron et al., 2006). Their capabilities can be defined by performance on behavioural tasks assessing low-level, basic visual information processing. An increasing trend in autism research has been defining the perceptual phenotypes in ASD and other neurodevelopmental conditions (NDCs) by conceptualizing atypical visuo-perceptual processes usingtwo models; the dorsal stream vulnerability hypothesis (Braddick et al, 2011) and the complexity-specific (CS) hypothesis (Bertone et al., 2005). Whereas the former is defined by findings of less efficient dynamic information processes across NDCs, the latter suggests neuro-integrative dysfunction leading to decreased sensitivity to complex visual information. Despite progress in defining visuo-perceptual profiles in ASD and other NDCs, findings are often inconsistent due to the use of different tasks across clinical groups, and participant groups in the literature are predominantly adults with average or above average cognitive abilities.

Objectives: Thepresent study (i) assessed visuo-perceptual profiles (processing of static and dynamic stimuli of varying complexity) in youth with ASD and other NDCs, and (ii) explored the extension of the CS hypothesis to a non-adult ASD population.

Methods: This study employed a single interval, two alternative (spatial) forced-choice orientation-discrimination paradigm to assess the processing of luminance- (simple) and texture-defined (complex) gratings presented in both static and dynamic states for 101 children and adolescents (aged 5 to 17 years). Participant groups either had a primary diagnosis of ASD (n=32), a non-ASD NDC (i.e., ADHD, ID and LD; NDC; n=26) or were typically developing (TD; n=43); groups were matched for mental age (MA), (p=.10), defined by an assessment of cognitive ability using the Wechsler Abbreviated Scale of Intelligence (WASI-II). Orientation-discrimination thresholds (luminance- and contrast-modulation thresholds) were calculated for each condition across groups; performance was assessed in relation to MA.

Results: The performance of the ASD group was comparable to the TD group, whereas the NDC group demonstrated reduced performance for second-order dynamic stimuli, suggesting that the CS hypothesis can define perceptual abilities of younger individuals with a non-ASD NDC. While results are not consistent with the adult-based CS hypothesis, significant correlations were found between MA and ASD perceptual discrimination thresholds in all conditions: r [-.49, -.41, -.55], with the exception of the luminance-defined, dynamic information condition.This relationship, demonstrating that discrimination thresholds decrease with increasing mental age, suggests the visuo-perceptual profile of individuals with ASD changes with MA.

Conclusions: This study provides valuable information regarding the respective maturation of both dynamic and static early perceptual abilities across childhood and adolescence in ASD compared to MA-matched NDC and TD groups. Findings extend the literature by evaluating the integrity of the dorsal and ventral visual streams in clinical groups, and contribute to the developmental and condition-specific conceptualization of visuo-perceptual processing in ASD. Overall, the results support the applicability of the CS hypothesis to other NDCs, and highlight the relationship between visuo-perceptual profiles and overall cognitive abilities (i.e., MA) in ASD. Future research should assess perceptual abilities in ASD and other NDCs within a developmental context.