Early-stage visual processing abnormalities in high-functioning autism spectrum disorder (ASD)

Abstract

It has been reported that individuals with autism spectrum disorder (ASD) have abnormal responses to the sensory environment. For these individuals sensory overload can impair functioning, raise physiological stress, and adversely affect social interaction. Early-stage (i.e. within 200ms of stimulus onset) auditory processing abnormalities have been widely examined in ASD using event-related potentials (ERP), while ERP studies investigating early-stage visual processing in ASD are less frequent. We wanted to test the hypothesis of early-stage visual processing abnormalities in ASD by investigating ERPs elicited in a visual oddball task using illusory figures. Our results indicate that individuals with ASD have abnormally large cortical responses to task irrelevant stimuli over both parieto-occipital and frontal regions-of-interest (ROI) during early stages of visual processing compared to the control group. Furthermore, ASD patients showed signs of an overall disruption in stimulus discrimination, and had a significantly higher rate of motor response errors.

Figure 1

We used Kanizsa and non-Kanizsa figures as stimulus material in this experiment. In particular, the stimulus types are Kanizsa square (target), Kanizsa triangle, non-Kanizsa square, and non-Kanizsa triangle. The non-target Kanizsa triangle is introduced to differentiate processing of Kanizsa figures and targets. The stimuli consist of either three or four inducer disks which are considered the shape feature, and they either constitute an illusory figure (square, triangle) or not (collinearity feature).

Figure 2

Sensor layout of the 128-channel geodesic sensor net (EGI, Eugene, Oregon) with frontal and parieto-occipital ROI for left, right, and midline labeled.

Figure 3

Parieto-occipital P50 amplitude is significantly more positive to non-target Kanizsa stimuli bilaterally in the ASD group compared to controls (F_1,29 =4.49, p=0.043).

Figure 4

3D topographic map of scalp potentials (P50, ~90 ms post-stimulus) in response to non-target Kanizsa stimuli in autism and control groups. The autism group shows more pronounced posterior positivity.

Figure 5

Latency of the parieto-occipital N100 ERP component to target Kanizsa, non-target Kanizsa, and non-Kanizsa standards in autism and control groups. A Stimulus (target, non-target, standard) X Group interaction is significant (F_2,58=3.43, p=0.04) across both hemisphres.

Figure 6

Midline frontal P50 amplitude is significantly more positive to non-target Kanizsa stimuli in the ASD group compared to controls (F_1,29 =6.24, p=0.019)

Figure 7

Midline frontal ERP waveforms to non-target Kanizsa illusory figures in autism and control groups (grandaverage, N=15/group).

Figure 8

3D topographic map of scalp potentials (N100, 130 ms post-stimulus) in response to target stimuli in autism and control groups. The autism group shows more pronounced anterior frontal negativity.

Figure 9

2D topographic map of responses to non-target Kanizsa, non-Kanizsa standards, and target Kanizsa stimuli in autism and control groups (210–220 ms post-stimulus). The control group shows frontal positivity (P200) only to targets, whereas the autism group has frontal postivity expressed as well to non-target stimuli (both non-target Kanizsa and non-Kanizsa standards).