Reduced Spatial Suppression in ASD Children
Objectives: The aim of our study was to examine the spatial suppression and gain control in a broader sample of ASD children with wider range of IQ scores.
Methods: Subjects were 22 ASD boys and 32 TD boys, aged between 6 and 15 years with IQ ranging from 62 to 136: intellectual ability was assessed by the Kauffman Assessment Battery (Kauffman&Kauffman, 2004). Experimental groups did not differ by chronological age, but mean IQ score was higher in TD than ASD children (117.5±12.0 and 90.9±19.8, respectively). The experimental procedure was similar to those used by Foss-Feig et al., 2013. The stimuli were the drifting vertical sine wave gratings of either small (2°) or big (12°) size, presented in high- (100%) or low- (1%) contrasts. The duration of stimuli presentation was adjusted using two interleaved one up two down staircases that converged on 71% correct performance. Participants were asked to judge the direction of motion. The logarithm of the obtained threshold was taken as a dependent variable for ANOVA analysis performed separately for high- and low- contrast condition with stimuli Size as within-subject factor and Group as between subject factor. To examine for gain control ANOVA with Contrast as within-subjects factor was applied to the thresholds for small stimuli obtained in low and high contrast blocks.
Results: In high-contrast condition the was significant Size by Group interaction (F(1,52) = 5.49, p = 0.023, η2 = 0.094), with ASD children having smaller difference between thresholds obtained for small and big stimuli (spatial suppression) as compared to TD boys (log scaled: 0.18±0.19 and 0.30±0.19, respectively for ASD and TD). No group difference in low-contrast condition was found. The group also did not differ either in gain control or in general sensitivity to motion.
Conclusions: Our study provides evidence for a reduced spatial suppression in a representative sample of ASD boys comparing to their TD peers.