Atypical sound discrimination in children with ASD as indicated by cortical ERPs

Background: Individuals with autism spectrum disorder (ASD) show a relative indifference to the human voice.
Accordingly, and contrarily to their typically developed peers, adults with autism do not show a preferential
response to voices in the superior temporal sulcus; this lack of voice-specific response was previously linked
to atypical processing of voices. In electroencephalography, a slow event-related potential (ERP) called the
fronto-temporal positivity to voice (FTPV) is larger for vocal than for non-vocal sounds, resulting in a voice-sensitive
response over right fronto-temporal sites. Here, we investigated the neurophysiological correlates of voice
perception in children with and without ASD.
Methods: Sixteen children with autism and 16 age-matched typically developing children heard vocal (speech and
non-speech) and non-vocal sounds while their electroencephalographic activity was recorded; overall IQ was
smaller in the group of children with ASD. ERP amplitudes were compared using non-parametric statistical tests at
each electrode and in successive 20-ms time windows. Within each group, differences between conditions were
assessed using a non-parametric Quade test between 0 and 400 ms post-stimulus. Inter-group comparisons of ERP
amplitudes were performed using non-paired Kruskal-Wallis tests between 140 and 180 ms post-stimulus.
Results: Typically developing children showed the classical voice-sensitive response over right fronto-temporal
electrodes, for both speech and non-speech vocal sounds. Children with ASD did not show a preferential response
to vocal sounds. Inter-group analysis showed no difference in the processing of vocal sounds, both speech and
non-speech, but significant differences in the processing of non-vocal sounds over right fronto-temporal sites.
Conclusions: Our results demonstrate a lack of voice-preferential response in children with autism spectrum
disorders. In contrast to observations in adults with ASD, the lack of voice-preferential response was attributed to an
atypical response to non-vocal sounds, which was overall more similar to the event-related potentials evoked by
vocal sounds in both groups. This result suggests atypical maturation processes in ASD impeding the specialization
of temporal regions in voice processing.