| Imitation is a very important way to learn within a social context. Researches increasingly suggest that understanding and imitating other people's actions is central to the development of social cognition, however, that is the weakest link to the individuals with autism. Based on the overview of many research documents related to Autistic spectrum disorder, we focus on the behavior characteristics, cognitive functions and neural mechanism during IMITATION by 3 series of experiments. Following the experiments' conclusion, this study carried out early intervention programs for the young children with autism to assess the benefit of the Reciprocal Imitation Skills to increasing their imitative behavior, and demonstrated the validity of experimental studies in return.There are five parts within this dissertation:The first part reviewed the research background about the imitation and the impaired imitative skills related to autism, especially comparing the difference of Imitation definitions, the changes in the research approaches, then, put forward our research overall idea and design.The second part is made up of experimental studies, the core of this research, including three series of studies and 10experiments. Subjects were fifteen Children (mean age=8.40y) diagnosed with Autistic spectrum disorder (ASD), matched with thirteen Children (mean age=9.44y) diagnosed as Mental Retardation (MR) on verbal IQ and CA(Chronological Age), and thirteen Children (mean age=9.08y) diagnosed as Deaf (D) on the non-verbal IQ and CA.From the view of observing behavior, Series 1 examined their responses on the tasks categorized on 2 imitation types(response agents and Goal-directed) and 4 kinds of motor imitation (manual postures, oral-face postures, object involved action and Goal-directed action).We concluded that: (1) the individuals with ASD achieved significantly lower scores in the manual gesture imitation than the Deaf, and little higher than the MR ; (2) Children with Autism achieved significantly lower scores in oral-face postures than Deaf Children, though higher than the MR; (3) the children with ASD achieved significantly lower scores in the object involved imitation than those who were MR and Deaf; (4) Autism has goal-directed imitation deficit and failed to understand other's action.From the standpoint of cognitive function, Series 2 analyzed the relationship between three imitation tasks (manual, oral-facial, and object oriented imitations) and three influencing factors(Joint Attention, Working Memory and Apraxia), the outcome indicated that: (1) the ability of Joint attention for individuals with ASD is intact; (2) the working memory has no influence on the imitation deficit with ASD; (3) the Dyspraxia is one of the primary reason for the Autism's imitation deficit, but not the only one; (4) Multiple Regression Equation applied and suggested that imitation skills were differentially impaired in children with autism, the poor performance of imitation skills clustered with overall developmental level(age) and apraxia.From the perspective of neural mechanisms, Series 3 devised three tasks with different effectors (observation and imitation of the game Rock_Paper_Scissors, observation of oral-face posture, and observation of Meaningful and Meaningless limb posture). Functional magnetic resonance imaging (fMRI) scanning protocol was used to localize brain areas that were active during the observation and imitation of actions made by another individual. We found that: (1) During the observation and imitation of hand geusture, the activity attributable to MNS was less extensive in the individual with autism than normal subjects; (2) On the task of oral-face observation, the activity attributable to MNS was less extensive in the children with autism than normal subjects; (3) when observing the Meaningful and Meaningless body gesture, the activity of MNS was less extensive in Autism than normal subjects, either.The third part is the early intervention program that is multiple-baseline designed across 4 young children with autism (mean age=49.25m). In sum, after four months intervention, all participants increased and maintained their spontaneous object imitation skills and generalized in the familty. Who attend the intervention earlier; he achieved the higher performance on the object imitation easiler. To some extent, participants exhibited increases in other social-communicative behaviors, including spontaneous language, joint attention, pretend play; and the stereotypical behaviors decreased.Based on the four level of imitation, behavior characteristics, ognitive and neural mechanism nature and intervention performance, the fourth part discusses the following problems objectively: the distinction between the developmental DELAY and the congenital DEFICIT, the relationship between IQ and imitative ability, the relationship between the poor imitation performance and social motivation lacking, the connection between Echolalia and Echopraxia in autism and imitation deficit. More importantly, within the frame of the TWO neural cognitive science theories, Direct Mapping and the Dual Route Procession, we need to reconsider the FOUR primary cognitive theories, which are the theory of Active Intermodal Matching (AIM), the theory of Self-Other Mapping, Goal-Directed Imitation Theory (GOADI), the Dual Route theory, and the reason for the effecitivity of the imitation intervention training.The fifth part draws five important conclusions and predicts the research tendency. The conclusions are as follows: (1) Imitation deficit was one of main characteristic of the individual with autism, the Pervasive Developmental Disorder; (2) Comparing the role of Joint attention and Working memory, age and dyspraxia are the primary factors influencing the poor imitation performance of the children with autism; (3)During all the observation tasks, the premotor cortex and inferior parietal cortex have the same activation in Normal subjects , which are also somatotopically organized. Thus, this is the first time to demonstrate the hypothesis of MNS lied in Chinese people; (4) In whatever observation or imitation, we found that activity attributable to MNS was less extensive in the children with autism than normal subjects, which supports the hypothesis of dysfunctional Mirror Neuron System; (5) Considering that the circuit of MNS plays an important role in social cognition, we suggest that the social disability consisting of imitation deficit happening in the children with ASD is associated with altered patterns of brain activity. It is more likely to be the more complex and distributed network linking the mirror neuron system that is functionally impaired. (6) On the point ot neural plasticity, since Reciprocal Imitation Training is effective to improve the object imitation skill for the young children with autism, which suggested that the imitation skills acquired from training is helpful to improve the funcational coordination of MNS, and therefore deepen the possibility of improving imitation performance.More studies can developed in the future areas: (a) Formulating the standard imitation scale, increasing the size of subject sample, to compare autism and other developmental disability on the level of behavior characteristics, and to find the way to diagnose and treat the imitation deficit on the level of medical and biological feedback; (b) Increasing the studies on the disability of social cognition in autism, together with behavior level and neural science, and clarifying the relationship between imitation deficit and social cognition impairment; (c) Reinforcing the role of parents and peer imitation in the early intervention of reciprocal imitation training.
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