Abstract
Asperger syndrome (AS) is a neurodevelopmental condition within the Autism Spectrum Disorders (ASD) characterized by specific difficulties in social interaction, communication and behavioural control. In recent years, it has been suggested that ASD is related to a dysfunction of action simulation processes, but studies employing imitation or action observation tasks provided mixed results. Here, we addressed action simulation processes in adolescents with AS by means of a motor imagery task, the classical hand laterality task (to decide whether a rotated hand image is left or right); mental rotation of letters was also evaluated. As a specific marker of action simulation in hand rotation, we assessed the so-called biomechanical effect, that is the advantage for judging hand pictures showing physically comfortable versus physically awkward positions. We found the biomechanical effect in typically-developing participants but not in participants with AS. Overall performance on both hand laterality and letter rotation tasks, instead, did not differ in the two groups. These findings demonstrated a specific alteration of motor imagery skills in AS. We suggest that impaired mental simulation and imitation of goal-less movements in ASD could be related to shared cognitive mechanisms.
Highlights
Autism Spectrum Disorders (ASD), including autism and Asperger syndrome (AS), are characterized by developmental impairments in communication and social interaction, together with repetitive stereotyped behaviours [1]
Clinical diagnosis was validated by means of the Autism Diagnostic InterviewRevised (ADI-R) [39] and the Autism Diagnostic Observation Schedule (ADOS) Module 3 [40]; general intelligence was measured by means of the Wechsler Intelligence Scale for Children-Revised (WISC-R) [41]
Post-hoc comparisons on the interaction among stimulus laterality, stimulus orientation, and group (Figure 2, lower row) showed that typical adolescents were significantly more accurate in judging left than right 90u oriented hands (t = 3.077, p = .005), whereas the opposite was true at 270u orientation (t = 22.505, p = .020), consistent with the biomechanical effect
Summary
Autism Spectrum Disorders (ASD), including autism and Asperger syndrome (AS), are characterized by developmental impairments in communication and social interaction, together with repetitive stereotyped behaviours [1]. Some studies reported defective performance and altered patterns of sensorimotor brain activity during imitation [10,11], whereas other reported spared imitative abilities [12], and typical patterns of sensorimotor cortical activation during observation and execution of hand actions [13,14]. Recent behavioural studies shed new light in this issue by demonstrating a dissociation between goal-directed and goal-less imitation in ASD: individuals with ASD show relatively spared performance in imitating goaldirected movements and actions with objects, whereas they show impaired imitation of goal-less or meaningless actions [9,12,15,16,17,18]
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