Processing of temporal structure of complex sound in children with autism spectrum disorders (ASD)
Abnormal development of speech perception is one of the key symptoms of Autism Spectrum Disorders (ASD), but its neural basis remains unknown. It has been hypothesized that speech perception difficulties in children with ASD are associated with an innate deficit in specialization of the left hemisphere of the brain, which is 'responsible' for speech (Eyler et al., 2012). The most common speech deficit in people with ASD is their impaired ability to understand and produce changes in voice pitch (prosody). Pitch processing of complex sounds, such as music and speech, take place in specialized areas of the auditory cortex – in 'pitch processing centers' (Patterson et al., 2002). Interestingly, this processing is performed differently in the right and left hemispheres, and the pitch processing in the left hemisphere is particularly important for speech perception (Schneider et al., 2005). Using MEG, we found that analysis of sounds characterized by complex spectral composition is impaired in children with ASD in the left hemisphere (Fig. 1, 2), suggestive of a specific deficit in functioning of the left 'pitch processing centers'. Developing this line of research, we plan to study how the identified neural deficit affects the speech abilities of children with ASD. This study will help to identify objective biomarkers useful for early diagnosis of speech deficits and their correction in children with ASD.
Fig. 1. Activation of the auditory cortex in response to 40 Hz clicks trains in neurotypical children.
Fig. 2. Auditory brain response to periodic stimulation is delayed in the left hemisphere in children with ASD compared to neurotypical (NT) children.
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2. Patterson, R.D., Uppenkamp, S., Johnsrude, I.S., Griffiths, T.D., 2002. The processing of temporal pitch and melody information in auditory cortex. Neuron 36: 767–776.
3. Schneider P, Sluming V, Roberts N, Scherg M, Goebel R, Specht H, Dosch H, Bleeck S, Stippich C, Rupp A. 2005. Structural and functional asymmetry of lateral Heschl’s gyrus reflects pitch perception preference. Nat Neurosci. 8:1241-1247