Brain and Behavioral Correlates of Auditory-Motor Synchronization in Children with Autism Spectrum Disorder

Background: Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social and communication skills as well as repetitive behaviors and restricted interests.  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.  Studies in vision point to an atypical functioning of the MNS in individuals with 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).  As in vision, recent evidence suggests that MNS regions may also be affected in the auditory domain in ASD (Wan et al, 2010).  However, no one has examined basic auditory-motor synchronization in ASD versus TD children.

Objectives: The objectives of the present research were: 1) to test for group differences between ASD and TD children on a basic auditory-motor synchronization task, and 2) to investigate the correlation between performance on this task with brain structure.

Methods: We present preliminary data from 27 ASD and 40 TD control children as part of the ‘NeuroDevNet ASD project’, an ongoing multi-site study on brain and behavioral development in ASD.  The groups were matched on age (from 6-16 years old), and all subjects had an IQ above 70.  In an auditory-motor synchronization task, subjects were asked to tap in synchrony with auditory rhythms of varying levels of complexity (easy, simple, and complex).  We acquired T1-weighted MRI anatomical scans from all children on a 3T scanner.  We performed cortical thickness (CT) analyses on these MR data and then correlated performance on the auditory-motor task with the CT results.  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) performed worse on more complex rhythms.  However, children with ASD showed better performance relative to TD on the most complex rhythms.  In TD, performance on the auditory-motor task was negatively correlated with CT in motor cortex.  In contrast, ASD individuals showed a positive correlation between performance and CT in motor cortex.

Conclusions: We provide preliminary brain-behavioral evidence that basic auditory-motor synchronization might be enhanced in children with ASD relative to TD.  Our cortical structure analyses signal potential alterations in the ‘auditory MNS’ system in ASD.  These findings are in contrast to the view that ASD individuals are generally impaired in cross-modal processing.  However, these findings are consistent with current models of enhanced basic (low-level) processing in ASD.