Children with autism rely more on internal cues about the orientation of their limbs when learning to use a novel tool in new situations, reports a study published online this week in Nature Neuroscience. In contrast, children without autism rely equally on external cues, such as vision. The study found that greater reliance on internal cues in the autistic group correlated with greater impairments in social functioning and imitation.
Reza Shadmehr and colleagues asked groups of autistic and non-autistic children to move a robotic 'arm' towards a target. The robotic arm was designed to resist their movements, so that the first attempts were disjointed and off-target; though with practice both groups quickly learned to compensate for this.
The team then noted how well the children could generalize this learned adjustment to new target locations. Two types of target locations were tested: one required the children to rotate their hand and arm joints in way that was identical to what had been learnt, though the movements looked quite different; the other required movements which looked similar to what had been learnt, but joint rotations required were different. Shadmehr and colleagues discovered that autistic children only utilized the previous learned adjustments when joint rotations were the same, whereas the non-autistic children adjusted to both types of targets
Generalized learning based on what movements look like relies on visual cues, whereas the generalized learning exhibited by the autistic children -- which is based on joint rotations -- requires a greater awareness of internal cues about the position of limbs in space.
Reza Shadmehr (Johns Hopkins University, Baltimore, MD, USA)
Abstract available online.
(C) Nature Neuroscience press release.
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