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Psychophysical and Speech Perception Studies in Individuals with Autism Spectrum Disorders

One of the remarkable properties of speech perception is its high resilience to the corrupting influences of background sounds. Everyday experience tells us that, even in noisy acoustic environments, we are able to understand speech, with little or no effort on our part. It appears that the human auditory system has developed useful strategies or mechanisms to optimize the saliency of the speech signal. Some of these mechanisms involve processing that occurs at very low levels of the auditory system, including the hearing end organ – the cochlea. Others occur at higher levels, up to and including the auditory cortex, and beyond. However, it is clear that the low-level processing stages are important, particularly for our perception of loudness, and the detection of speech in noise. Individuals with autism appear to react adversley to sounds, and have difficulty understanding speech when there are competing sounds present. Currently, we are not certain whether these symptoms are due to alterations in low- or high-level auditory processing. However, the evidence for the former is compelling, although we do not as yet know the nature of the underlying mechanisms responsible for the observed speech-in-noise deficits and atypical loudness perception. This project involved a series of behavioral and objective studies of auditory perception using both simple and complex stimuli to identify those mechanisms responsible for the perceptual difficulties experienced by individuals with autism. The results of the project have the potential to lead to the development of new screening tools for auditory sensitivity in autism, which will be important not only for improved clinical diagnosis, but also for the use in epidemiological and genetic research into autism, and may also help in the design of digital speech processing algorithms to compensate for auditory processing abnormalities.