Objectives: We assessed a broad range of low-level auditory and speech processing abilities, as well as general language skill, to investigate whether the observed pattern of assets and deficits favors the evidence for the Atypical Hemispheric Specialization hypothesis or rather for the WCC or EPF theories.
Methods: A series of psychophysical measures and language tasks were administered in 20 adolescents with ASD and early developmental language delay and 20 matched TD controls. Auditory measures were selected to preferentially target right auditory cortex (frequency discrimination, 4 Hz AM) and left auditory cortex processing (gap-in-noise detection, 20 Hz AM). Speech perception measures comprised the perception of words and sentences in various types of noise (i.e. stationary, fluctuating and babbling noise) to investigate the impact of increasing contextual information and spectrotemporal complexity of the background noise, respectively. Language measures comprised various phonological tasks and general expressive and receptive language tasks.
Results: Preliminary analyses confirmed that the ASD group shows severe and broad language impairments, as well as deficits in speech perception, in particular for sentence perception in spectrotemporally complex background noise. There were no group differences on any of the low-level auditory measures.
Conclusions: The pattern of superior spectral and inferior temporal auditory processing could not be replicated in this sample of adolescents with ASD and early language impairment. Given the similar performance in both groups, the obtained auditory profile could not be related to any advantageous or preferential hemispheric processing. Yet, the severe deficits in basic speech-in-noise perception are intriguing and point to an inability to efficiently integrate socially relevant auditory information.
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