Building a Percept: Early Influences on Mid and Higher-Level Visual Abilities in Autism Spectrum Disorder

Background:  Individuals with Autism Spectrum Disorder (ASD) present a perceptual profile that is defined by atypical performance on tasks mediated by lower- (primary visual areas), mid- (extra-striate areas) and higher-level (large-scale neural mechanisms) visual analysis (Simmons et al., 2009). These differences characterize the distinct visuo-perceptual phenotype in ASD, broadly described as strengths in detailed, local processing (mediated by lower-level analysis) with or without concurrent difficulty in global or integrative processing (mediated by mid- and higher-level analysis). The visuo-perceptual phenotype in ASD has been based largely on isolated levels of processing, providing little information with respect to how performance within the same individual varies with increasing task complexity. Alterations occurring in earlier stages of visual analysis arguably affect those occurring at higher levels (Bertone et al., 2010).  It is therefore important to elucidate the relationship between perceptual abilities mediated by different levels of analysis to understand how alterations in the building blocks of perception affect higher-order cognitive and social functions in ASD.

Objectives:  The present work systematically investigated whether enhanced local processing in lower-levels of visual analysis influenced higher-level perception in the same group of children and adolescents with and without ASD. Specifically, we examined whether enhanced local perception at earlier stages of processing affected higher level perception by asking the following questions:

1) Does enhanced local processing in low-level visual analysis predict greater local interference in mid-level visual analysis?

2) Does greater local interference in mid-level visual analysis predict a decreased global performance in higher-level visual analysis?

Methods:  A total of 27 and 48 respective children and adolescents with and without ASD performed three tasks, each soliciting a progressively complex visual analysis: (i) low-level perception was assessed by measuring contrast sensitivity to vertically oriented, sine-wave luminance- defined gratings of different spatial frequencies; (ii) mid-level perception was assessed by measuring local and global reaction times for consistent and inconsistent stimuli in a Navon task (Navon, 1977); and (iii) higher-level perception was assessed by measuring thresholds in a face-identity discrimination task.

Results:   Simultaneous multiple regression analyses revealed no significant relationship between low- and mid-level processing in either the TD or ASD groups; specifically, enhanced local processing on the low-level task, reflected by an increased sensitivity at high spatial frequencies, did not predict slower performance on the mid-level task when local information conflicted with the identification of global information (i.e. increased local interference). The effect of mid- on high-level perception, however, revealed that an increased local interference on the mid-level task predicted a decreased performance on the higher-level, face identity discrimination task in the ASD group alone. These results suggest that an increased effect of local processing for mid-level perception in ASD impacts higher-level perception, typically requiring a global analysis.

Conclusions:  Our findings establish a significant association between mid- and higher-level mechanisms in ASD. Such a relationship suggests that alterations in the “building blocks” of early perception are responsible for differences in higher-order visual processes in ASD, and possibly, functions in the domains of socialization and communication.