Between- and within-person inhibition of return effects in the movements of people with autism.

Autism is neurodevelopmental disorder that is characterized by severe deficits in the areas of social interaction and language, repetitive behaviors, and impaired motor control. Some researchers have suggested that the problems in social interaction may be related to a dysfunction in the mirror neuron system. The mirror neuron system is a network of neurons in the premotor and posterior parietal cortices that become active when performing movements and when observing other people performing similar movements. In autism, a dysfunction of the mirror neuron system may lead to a lack of understanding of the actions of other people and, as a result, to a deficiency in understanding other people's intentions and mind states. The current study tested the mirror neuron dysfunction hypothesis by investigating the relative magnitude of between- and within-person inhibition of return (IOR) effects in people with autism. Inhibition of return is the term given to the increased reaction times for responses to target stimuli that appear at the same location as a previous cue or target stimulus relative to those presented at a new location. Recently, we have found that participants working in pairs demonstrate similar magnitudes of IOR when they respond to targets that are presented at the same location as a previous response whether they or their partners recently moved to that location (within- and between-person IOR, respectively). The between-person IOR effects have been attributed to activation of the mirror neuron system. The results of the present study revealed that, unlike their peers from the typical population, the participants with autism had smaller magnitude IOR effects when they completed a movement that followed the movement of their partner than when they followed their own movement. These data support the hypothesis that the mirror neuron system in people with autism may not function as efficiently as the mirror neuron system in people from the typical population. [ABSTRACT FROM AUTHOR]