Atypical brain responses to auditory spatial cues in adults with autism spectrum disorder.

The auditory processing atypicalities experienced by many individuals on the autism spectrum disorder might be understood in terms of difficulties parsing the sound energy arriving at the ears into discrete auditory 'objects'. Here, we asked whether autistic adults are able to make use of two important spatial cues to auditory object formation - the relative timing and amplitude of sound energy at the left and right ears. Using electroencephalography, we measured the brain responses of 15 autistic adults and 15 age- and verbal-IQ-matched control participants as they listened to dichotic pitch stimuli - white noise stimuli in which interaural timing or amplitude differences applied to a narrow frequency band of noise typically lead to the perception of a pitch sound that is spatially segregated from the noise. Responses were contrasted with those to stimuli in which timing and amplitude cues were removed. Consistent with our previous studies, autistic adults failed to show a significant object-related negativity (ORN) for timing-based pitch, although their ORN was not significantly smaller than that of the control group. Autistic participants did show an ORN to amplitude cues, indicating that they do not experience a general impairment in auditory object formation. However, their P400 response - thought to indicate the later attention-dependent aspects of auditory object formation - was missing. These findings provide further evidence of atypical auditory object processing in autism with potential implications for understanding the perceptual and communication difficulties associated with the condition.