Evidence for diminished multisensory integration in autism spectrum disorders.

Individuals with autism spectrum disorders (ASD) exhibit alterations in sensory processing, including changes in the integration of information across the different sensory modalities. In the current study, we used the sound-induced flash illusion to assess multisensory integration in children with ASD and typically-developing (TD) controls. Thirty-one children with ASD and 31 age and IQ matched TD children (average age = 12 years) were presented with simple visual (i.e., flash) and auditory (i.e., beep) stimuli of varying number. In illusory conditions, a single flash was presented with 2-4 beeps. In TD children, these conditions generally result in the perception of multiple flashes, implying a perceptual fusion across vision and audition. In the present study, children with ASD were significantly less likely to perceive the illusion relative to TD controls, suggesting that multisensory integration and cross-modal binding may be weaker in some children with ASD. These results are discussed in the context of previous findings for multisensory integration in ASD and future directions for research.

Multisensory temporal integration in autism spectrum disorders.

The new DSM-5 diagnostic criteria for autism spectrum disorders (ASDs) include sensory disturbances in addition to the well-established language, communication, and social deficits. One sensory disturbance seen in ASD is an impaired ability to integrate multisensory information into a unified percept. This may arise from an underlying impairment in which individuals with ASD have difficulty perceiving the temporal relationship between cross-modal inputs, an important cue for multisensory integration. Such impairments in multisensory processing may cascade into higher-level deficits, impairing day-to-day functioning on tasks, such as speech perception. To investigate multisensory temporal processing deficits in ASD and their links to speech processing, the current study mapped performance on a number of multisensory temporal tasks (with both simple and complex stimuli) onto the ability of individuals with ASD to perceptually bind audiovisual speech signals. High-functioning children with ASD were compared with a group of typically developing children. Performance on the multisensory temporal tasks varied with stimulus complexity for both groups; less precise temporal processing was observed with increasing stimulus complexity. Notably, individuals with ASD showed a speech-specific deficit in multisensory temporal processing. Most importantly, the strength of perceptual binding of audiovisual speech observed in individuals with ASD was strongly related to their low-level multisensory temporal processing abilities. Collectively, the results represent the first to illustrate links between multisensory temporal function and speech processing in ASD, strongly suggesting that deficits in low-level sensory processing may cascade into higher-order domains, such as language and communication.

Brief report: Arrested development of audiovisual speech perception in autism spectrum disorders.

Atypical communicative abilities are a core marker of Autism Spectrum Disorders (ASD). A number of studies have shown that, in addition to auditory comprehension differences, individuals with autism frequently show atypical responses to audiovisual speech, suggesting a multisensory contribution to these communicative differences from their typically developing peers. To shed light on possible differences in the maturation of audiovisual speech integration, we tested younger (ages 6-12) and older (ages 13-18) children with and without ASD on a task indexing such multisensory integration. To do this, we used the McGurk effect, in which the pairing of incongruent auditory and visual speech tokens typically results in the perception of a fused percept distinct from the auditory and visual signals, indicative of active integration of the two channels conveying speech information. Whereas little difference was seen in audiovisual speech processing (i.e., reports of McGurk fusion) between the younger ASD and TD groups, there was a significant difference at the older ages. While TD controls exhibited an increased rate of fusion (i.e., integration) with age, children with ASD failed to show this increase. These data suggest arrested development of audiovisual speech integration in ASD. The results are discussed in light of the extant literature and necessary next steps in research.