Left hemispheric deficit in the sustained neuromagnetic response to periodic click trains in children with ASD.

Abstract

Deficits in perception and production of vocal pitch are often observed in people with autism spectrum disorders (ASD), but the neural basis of these abnormalities is unknown. In magnetoencephalogram (MEG), spectrally complex periodic sounds trigger two continuous neural responses - the Auditory Steady State Response (ASSR) and the Sustained Field (SF). It has been shown that the SF in neuro-typical individuals is associated with low-level analysis of pitch in the pitch processing center of the Heschls gyrus. Therefore, this auditory response may reflect vocal pitch processing abnormalities in ASD. The SF, however, has never been studied in people with these disorders. We used MEG and individual brain models to investigate the ASSR and SF evoked by monaural 40 Hz click trains in 7-13-year-old boys with ASD (N=35) and neuro-typical (NT) boys (N=35). In agreement with the previous research in adults, the cortical sources of the SF in children were located in the left and the right Heschls gyri, anterolateral to those of the ASSR. In both groups, the SF and ASSR dominated in the right hemisphere and were higher contralaterally to the stimulated ear. The ASSR increased with age in both NT and ASD children and did not differ between the groups. The SF was moderately decreased in both hemispheres and was markedly delayed and displaced in the left hemisphere in boys with ASD. The SF delay in participants with ASD was present irrespective of their intelligence level and severity of autism symptoms. We suggest that the selective left-hemispheric SF abnormalities in children with ASD reflect a low-level deficiency in pitch processing that may contribute to their difficulties with perception and production of linguistic prosody.