Low-Level Auditory-Motor Synchronization in Children with Autism Spectrum Disorder

Background: The “mirror-neuron system” (MNS) refers to a group of neurons that fire when performing an action as well as observing that same action performed by another (Rizzolatti et al., 2004).  Studies in vision point to an atypical functioning of the MNS in individuals with autism spectrum disorder (ASD) versus typical development (TD).  A parallel MNS-like system is thought to exist in the auditory domain in the context of auditory-motor synchronization (Chen et al., 2008).  Just as in vision, recent evidence suggests that the MNS may also be affected in the auditory domain in ASD (Russo et al., 2008; Wan et al, 2010).  However, no one has examined low-level auditory-motor synchronization in ASD versus TD children.

Objectives: The objectives of the present research were 1) to adapt a previously used auditory-motor synchronization task (Chen et al., 2008) for use in a child population, and 2) to test for group differences between ASD and TD children on this auditory-motor synchronization task.

Methods: We are currently collecting auditory behavioral data and MRI measures in a large group of children with ASD versus TD controls in a multi-site study on brain and behavioral development (Zwaigenbaum et al., 2011).  Here we present preliminary data from 7 children with ASD (mean age 10.0, range 6-15 years; mean IQ 105, SD 12.4) and 10 TD children (mean age 11.2, range 7-16 years).

In a child-friendly version of an auditory-motor synchronization task (Chen, et al., 2008), subjects were asked to tap in synchrony with auditory rhythms of varying levels of complexity (easy, simple, and complex).  Subject performance was measured based on mean absolute asynchrony (tap onset minus target onset).  Ethical approval for this research was obtained by the Montreal Neurological Institute and Hospital Research Ethics Board.

Results: Preliminary results revealed that all children (both ASD and TD) exhibited a complexity effect with worse performance (greater asynchrony) on more complex rhythms.  However, children with ASD show overall better performance (lower asynchrony) relative to TD.

Conclusions: We provide preliminary behavioral evidence that low-level auditory-motor synchronization is atypical in children with ASD relative to TD.  These findings are provocative since they are in contrast to the view that ASD individuals are generally impaired in cross-modal processing.  However, the finding that children with ASD show enhanced auditory-motor integration in this low-level context is consistent with current models of enhanced low-level processing in ASD.  These results signal potential alterations in the ‘auditory MNS’ system in ASD.  To this aim, we are currently conducting correlations between these auditory-motor behavioral measures and brain structural measures in the same participants.