I . From action to imitation
Despite the considerable delay and noise involved in cerebral information processing, we are generally capable of rapid and precise motor control. This is probably because predictive motor control is performed in the brain, using the difference between predicted sensory feedback and actual feedback occurring in association with hand movements, and enables highly accurate prediction of states of the hand based on an internal model of the hand (Inui 2006). Currently, a fronto-parietal network is known to be crucial for reaching-grasping: therefore, to shed light on the neural basis of the imitation required for learning of social skills and motor learning of tool use, we will perform two experiments:
1) Tracing and copying figures
Both tracing and copying figures are similar to imitating, in that they require re-constructing a sample object. Individuals with Williams syndrome, a developmental disorder, are known to be able to trace a figure but not to copy it (Nagai et al., 2001). On the other hand, functional neuroimaging study of tracing movements with normal subjects has revealed that the pre-supplementary motor area (pre-SMA) is involved in internal prediction of target motion during visual occlusion, and that the posterior parietal cortex is related to evaluation of online motor error based on visual feedback (Ogawa et al., 2006). Therefore, to clarify the difference in mechanisms between tracing and copying, we will use new tracing / copying tasks, varying i) visual features and ii) the speed and duration of sample (target) presentation.
Furthermore, to determine the neural basis of performance of each task, we will investigate neural activity by functional neuroimaging in normal subjects. In addition, we will investigate differences in brain activity between predictions of self-versus-othersf motion to clarify the neural basis underlying the self-other distinction.
2) Imitation of actions and gestures (including contract research)
Although the ability to imitate is known to be important for development of social behaviour, few studies have compared this ability in individuals with autism and Williams syndrome, who exhibit antithetical types of social disorders.
We will therefore compare the abilities to imitate actions and tool-use gestures of these two groups of patients, and attempt to determine whether a correlation exists between ability to imitate and social cognitive saliency.
