Audiovisual Processing in Specific Language Impairment. A growing body of literature strongly suggests that the ability to combine auditory and visual information plays a significant role in normal language acquisition. However, whether a breakdown in the merging of these senses may contribute to the development of language disorders, such as specific language impairment (SLI), is unknown. So far, only a few studies have evaluated audiovisual processing in SLI. All of them used the sensory conflict paradigm - the so-called McGurk illusion - in which the sound of pa is dubbed onto the visual articulation of ka typically leading to the perception of ta. These studies have reported a reduced susceptibility to this illusion in children with SLI and in adults with a history of SLI, concludin that their audiovisual integration is impaired. However, the inability to resolve a sensory conflic between auditory and visual modalities during syllable perception does not presuppose an impairment in audiovisual integration during other stages of linguistic processing, such as early sensory encoding of speech sounds or later lexical perception. Furthermore, how an impairment in audiovisual processing interacts with speech-language deficits of children with SLI is unknown. This project is designed to advance our understanding of audiovisual processing in SLI in multiple ways. First, we determine the effectiveness of audiovisual processing in SLI at the acoustic, phonemic, and lexical levels of speech perception by drawing on the strength of the event-related brain potentials (ERP) method, whose excellent temporal resolution makes it uniquely suited for evaluating the stage of information processing at which audiovisual perception falters in SLI. We also add more ecologically valid stimuli - syllables without a sensory conflict and words - to our paradigms in order to examine audiovisual processing in response to more realistic speech stimuli. Lastly, by evaluating correlations between, on the one hand, behavioral and ERP indices of audiovisual integration and, on the other hand, a range of cognitive and language skills in children with SLI, we strive to identify those cognitive and linguistic deficits of SLI that are most likely to be affected by audiovisual perception difficultis in this group.
Specific language impairment affects more children than autism and stuttering combined and often has a life-long impact on individuals' well-being. The goal of this research is to identify the role of inefficient audiovisual processing in the development of specific language impairment and to help determine whether these children's language acquisition and speech perception difficulties may be alleviated by therapy techniques that focus on enhancing audio-visual perception skills.
