Making sense of sensory integration: Is perceptual coherence important in ASD?

Background:

Reports of ‘fragmented’ multisensory perception in autism spectrum disorders (ASDs) have increased interest in this area (Iarocci & McDonald, 2006). Recent research has produced conflicting results. Van der Smagt, van Engeland and Hemner (2006) found no difference in susceptibility to the Shams audio-visual illusion between control and high-functioning autism/AS groups. However, Smith and Bennetto (2007) suggest a ‘pre-attentive crossmodal’ component partially accounts for atypical audiovisual speech comprehension thresholds in adolescents with high-functioning autism.

Objectives:

Our study used an audio-visual ‘launch/pass’ phenomenon (Sekuler, Sekuler & Lau, 1997), in which a disk is made to appear to crash into and launch a second disk of the same colour by presenting an auditory stimulus at the point of occlusion. Such phenomena putatively reflect early perceptual integration (Bushara et al., 2003). We hypothesised that ASD children/adolescents with normal/near normal IQ would report fewer crashes in response to these stimuli than age-matched controls, as a consequence of compromised audio-visual processing.

Methods:

Age-matched participants with/without ASDs (n = 19 per group) were presented with five blocks of twenty trials in which experimental and control trials were inter-mixed. In experimental trials, an auditory signal was presented at one of three stimulus onset asynchronies (SOAs) relative to the point at which a disk passed over a stationary disk of the same colour (0ms, -250 ms and +250ms). The number of crash percepts reported in response to each condition was the dependent measure. The control trials presented unambiguous crash and miss events accompanied by auditory signals with the same SOAs.

Results:

No significant differences in the proportion of crashes reported in response to the simultaneous SOA condition, or the response pattern across SOAs, were obtained.

Conclusions:

This study found no evidence to support compromised audio-visual integration in ASD. Interim findings relating to diagnostic subgroups, IQ matching and ADHD comorbidity measures will be presented.