A review of behavioural and electrophysiological studies on auditory processing and speech perception in autism spectrum disorders

This literature review aims to interpret behavioural and electrophysiological studies addressing auditory processing in children and adults with autism spectrum disorder (ASD). Data have been organised according to the applied methodology (behavioural versus electrophysiological studies) and according to stimulus complexity (pure versus complex tones versus speech sounds). In line with the weak central coherence (WCC) theory of autism we aimed to investigate whether individuals with ASD show a more locally and less globally oriented processing style in the auditory modality. To avoid the possible confound of stimulus complexity, this influence was taken into account as an additional hypothesis. The review reveals that the identification and discrimination of isolated acoustic features (in particular pitch processing) is generally intact or enhanced in individuals with ASD, for pure as well as for complex tones and speech sounds. It thus appears that the local processing advantage is not influenced by stimulus complexity. Individuals with ASD are also less susceptible to global interference of speech-like material. A deficit in global auditory processing, however, is less universally confirmed. We propose that the observed pattern of auditory enhancements and deficits in ASD may be related to an atypical pattern of right hemisphere dominance. As the right and left hemisphere are relatively more specialized in spectral versus temporal auditory processing, respectively, right hemisphere dominance in ASD could provoke enhanced pitch and vowel processing, whereas left hemisphere deficiencies might explain speech perception problems and temporal processing deficits. (C) 2010 Elsevier Ltd. All rights reserved.