Children with Autism Spectrum Disorders and the Rubber Hand Illusion: Evidence of Decreased Multisensory Integration

Background:

Children with autism spectrum disorders (ASD) experience sensory and perceptual events differently than typically developing (TD) children.  One presumed source of altered perceptual experience is aberrant integration of information from multiple sensory modalities.  In the rubber hand illusion, simultaneous visual and tactile input converge to modify perception in a third modality, proprioception.  We hypothesized that children with ASD would differ from controls in their susceptibility to this illusion.

Objectives: To examine multisensory integration of visual and tactile input in ASD using the rubber hand illusion.
Methods: Thirteen children with ASD and thirteen children with TD, ages 8-17, were tested on the rubber hand paradigm.  The groups were matched for age, IQ, gender, and handedness.  ASD diagnosis was confirmed with the Autism Diagnostic Interview - Revised (ADI-R), Autism Diagnostic Observation Schedule (ADOS), and the judgment of a licensed clinical psychologist.  In the experimental condition, the experimenter used a soft brush to synchronously stroke a visible rubber hand and the child’s own hand, which was hidden from view.  In the control condition, the strokes to the real and rubber hands were delivered asynchronously.  Before and after each condition, the child was asked to make a judgment about the position of his/her obscured hand.  The dependent variable was the drift of perceived position relative to the position of the visible rubber hand, and was assessed using one sample t-tests.
Results: In the control condition (asynchronous brushing), neither group exhibited significant drift toward the rubber hand. In the experimental condition (synchronous brushing), the control group showed a significant drift in the direction of the rubber hand, while the autism group did not.  The amount of drift in the autism group was negatively correlated with spontaneous imitation during development as rated on the ADI-R.
Conclusions: The rubber hand illusion depends on the integration of visual and tactile input to influence proprioception.  Unlike the control group, children with ASD did not show a significant influence of this integrated multisensory input on proprioception, suggesting decreased integration of visual and tactile input.  Additionally, a trend for an association between the development of imitation skills and the strength of the illusion was noted in the ASD group.  The rubber hand illusion activates premotor cortex, a site that is part of the mirror neuron system, which has been implicated in autism and is thought to be important for developing imitation skills.  The link between the illusion and imitation skills may reflect a contribution of this system to multisensory integration deficits in ASD.