Children with Autism Show Enhanced Proprioceptive-Guided Motor Learning

Background: Difficulty with performance of skilled motor gestures is commonly reported in autism.  Previous studies of children with autism have demonstrated anomalous patterns of motor sequence learning on visually-guided motor tasks (e.g., serial reaction time, rotary pursuit) while a recent study of controlled reaching in a varying force field found an increased reliance on proprioceptive feedback in children with autism (Mostofsky et al., 2000, Larson and Mostofsky, 2008, Haswell et al., 2009).

Objectives: To use a blindfolded maze tracing task to examine whether children with autism show atypical proprioceptive-guided motor sequence learning and how that motor performance is related to core social/communicative impairment in autism.

Methods: 22 children with autism (5 female) and 23 typically developing (TD) children (5 female), 8-13 years, completed a task in which they used a stylus pen to trace a continuous closed-loop maze composed of linear segments while blindfolded.  The task consisted of 4 blocks of trials, with 4 trials in each block.  During blocks 1, 2, and 4 subjects traced a primary maze with eight decision points at which they could either make a correct turn or an error into a dead end; during block 3 subjects traced an “interference maze“ that was a mirror image of the primary maze.  After completing the task, children were shown a picture of 5 mazes and were asked to identify the primary maze, first using solely visual feedback, then with the addition of proprioceptive feedback (when allowed to trace the pictures with their hands).  Learning was assessed based on the number of loops completed in each trial and success in maze identification.  Associations between performance and degree of autism symptom severity/social impairment were examined using the Autism Diagnostic Observation Schedule (ADOS) and the Social Responsiveness Scale (SRS) parent report.

Results: Children with ASD showed no impairment in maze learning compared to TD children: (RM)ANOVA revealed no effect of diagnosis for number of loops competed across trials or blocks (all F<1.314, p>0.256).  Furthermore, for children with autism, we found positive correlations between average number of loops completed per trial and ADOS Total score, ADOS Social Interaction score and SRS T-score, such that greater autism symptom severity/social impairment was associated with better performance (R=0.443,p=0.039; R=0.542,p=0.009; R=0.540,p=0.012).  Children with autism also showed an intriguing, although non-significant increase in successful maze identification when using proprioceptive in addition to visual feedback:  the increase in successful identification was 40% for the autism group versus 15% for TD.  Additionally, at a trend level, those children who benefitted from proprioceptive feedback had a higher average ADOS Social Interaction score (greater social impairment) than those who did not (F=2.080, p=0.092).

Conclusions: These findings suggest that children with autism may be excessively dependent on proprioceptive feedback for motor learning.  Given that social and communicative gestures are often learned through visual imitation, these findings have important implications for understanding the neural basis of autism-associated impairments in motor, social and communicative development and for guiding therapies targeted at improving social and communicative skills in children with autism.