Multisensory Processing in Autism Spectrum Disorders : Intersensory Processing Disturbance as a Basis for Atypical Development

Autism spectrum disorder (ASD) is a neurodevelopmental disorder with symptom onset prior to age 3. Although there is great variability in symptom severity and intellectual functioning, ASD is defined by a triad of symptoms, including impairments in social functioning and interaction, impairments in communication, and restricted, repetitive, and stereotyped behaviors, interests, and activities (DSM-IV-TR: American Psychiatric Association, 2000). In this chapter we develop the view that typical social and communicative functioning rests on a foundation of intersensory/multisensory processing skills that develop and emerge across the first 6 months of life and are further refined across development (see also Bahrick, 2010). Intersensory processing entails perception of unified and coordinated information across the senses, including visual, auditory, tactile, and proprioceptive stimulation. Critical skills, such as social orienting and joint attention, which are found to be impaired in autism, also rely on a foundation of intersensory functioning (see also Mundy & Burnette, 2005). Attention, perception, learning, and interacting with the social world of people, language, and meaningful action depend on integrating dynamic, rapidly changing auditory, visual, tactile, and proprioceptive information from social and nonsocial events. Below we briefly describe the typical development of these skills across infancy and their links to social and communicative functioning. We then examine evidence of intersensory skills and impairments in individuals with ASD. Finally, we evaluate intersensory processing disturbance as a potential basis for explaining fundamental impairments in autism, including social and communicative functioning as well as stereotyped, repetitive behaviors. By 3 years of age, children with ASD show a variety of impairments in social and communicative functioning, including reduced eye contact and attention to social partners, poor joint attention skills, little imitation, poor facial recognition, and altered emotional responsiveness (e.g., Dawson et al., 2004; Mundy, 1995; Mundy & Burnette, 2005; Volkmar, Paul, Klin, & Cohen, 2005). Children with ASD also show atypical patterns of attention and sensory processing. Compared to typically developing (TD) children, children with ASD are said to show sticky attention or overselectivity, including impairments in disengaging attention from competing stimulation to orient to new events (Landry & Bryson, 2004; Rincover & Ducharme, 1987), particularly to social events (Dawson, Meltzoff, Osterling, Rinaldi, & Brown, 1998; Dawson et al., 2004; Swettenham et al., 1998). They also show heightened attention to detail relative to global information (see Brock, Brown, Boucher, & Rippon, 2002; Frith & Happé, 1994; Happé, 1999; Happé & Frith, 2006), enhanced visual search, and certain enhancements in visual and auditory processing, including discrimination of surface properties such as pattern and feature information (Mottron, Dawson, Soulières, Hubert, & Burack, 2006; O’Riordan, Plaisted, Driver, & Baron-Cohen, 2001). However, this heightened or enhanced processing is thought to reflect low-level perceptual processing of simple objects and events, and sensory impairments are evident as the complexity of the stimuli grows (Bertone, Mottron, Jelenic, & Faubert, 2005; Minshew & Hobson, 2008). For example, the processing of faces is impaired (Dawson, Webb, & McPartland, 2005; see Schultz, 2005, for a review). How and when do these impairments in attention, sensory processing, and social and communicative functioning develop, and how are they interrelated? Characterizing early behavioral markers and the nature of developmental cascades that lead to increasing symptom severity in ASD is currently a significant