The Cognitive Neural Mechanism Of Co-representation In The Asymmetry Joint Action

Joint action between individuals in everyday life are popular.Joint action describes as "any form of social interaction whereby two or more individuals coordinate their actions in space and time to bring about a change in the environment"(Sebanz,Bekkcring,&Knoblich,2006).According to the difficulty of inter-individual tasks,the symmetry joint action can be definded with the equally difficulty between actor and co-actor's tasks,such as the Joint Simon Task.And the asymmetry joint action is respect to task difficulty when one co-actor performs a more difficult task than the other.However,both the symmetry and asymmetry joint actions are often accompanied by planned coordination,which is individuals in joint action take action to achieve their common goals.It has been found that planned coordination between individuals is often accompanied by co-representation in joint action.Therefore,explore the cognitive neural mechanism of co-representation to provide a theoretical and empirical basis for the intervention of synergistic activities between individuals in the future.Based on the symmetry joint action task,two viewpoints about co-representation have been proposed.One is the action co-representation,and the other is the task co-representation.However,there are some conflicts of reaction choices between actor and co-actor in joint Simon task.Actor(or co-actor)must monitor co-actor(or actor)to ensure the successful completion of the task,based on which the co-representation effect obtained is likely to be caused by the stimulus-response model of the task rather than the planned coordination.In addition,one obtains the task or response presentations of the other one by visually observation in most cases.The task information of one actor,however,also could be obtained by the other side through abstract cues.Therefore,whether cues could give rise to co-representations between individuals,like visual observation does,is one of the questions that the present research aims to explore.At present,most of the studies,based on isolated experimental paradigm,examined the influence of co-representation between individuals on the activation patterns of their brains.However,the synchronization of behaviors is closely related to the synchronization of neural activity in brains.The neural activities between individuals would occur coupling with responding perception,action,and cognitive activities under the co-representation effect.Therefore,in order to unveil the neural basis of coupling process between individuals,it is especially necessary to interpret the co-representation of joint action in the perspective of inter-individual brains.In order to solve the above problems,this research introduces an asymmetric joint action task.Co-representation between individuals,in this task,will not been disturbed by task settings.Based on this task,the cognitive neural mechanism of inter-individual co-representation(in the present research)is systematically discussed.We manipulated the co-actor's features of stimulus and motion characteristics,actor's motion direction,the visual information interaction between oneself and the counterpart,and the clues,and so on.The present research explores the above problems through five experiments in three studies.The purpose of Study 1 is based on motion capture system to explore whether co-actor has influence on the action performance of actor in the situation where they could see each(i.e.visual information real-time interacting)and why this happens.Experiment la examines whether the co-representation effect between individuals could be found in the asymmetric joint action task with visual observation.21 pairs of subjects are selected to complete the asymmetric joint action under the 2(occlusion:yes,no)×2(obstacle:yes,no)within-subject design,to investigate the impact of co-actor on the actor's performance.The results show that the movements peak height of the actor is affected by the co-actor,and the co-presentation effect occurs.Experiment lb with 18 pairs of subjects,based on experiment la,changed the motion direction of actor to examine the stability of the effect.The results show that the co-presentation effect does not vary with the motion directions between individuals.Experiment 2a and 2b controls the stimulus and motion features,respectively,to determine the content of co-presentation effect.In experiment 2a,the stimulus features of co-actor have three levels which are conditions with no obstacle,obstacle with height of 10cm,and obstacle with height of 20cm.In addition,the height of movement must be higher than 23cm when subjects execute the task.Experiment 2b retain the no onstacle condition and 20cm obstacle condition on the basis of experiment 2a,and the motion features of co-actor are adjusted and the motion peak height must be higher than 23cm when reach the furthest target point and 33cm when reach the nearest target point.19 pairs of subjects were selected to take part in experiment 2a and 2b,respectively.The results show that the actor processes the features of stimulus in the co-actor's task,which supports the viewpoint of task co-presentation.The results of the two experiments indicate that in asymmetric joint action task,the actor would observe the co-actor and process the stimulus features of co-actor's task,thus the co-presentation effect occurs,and this effect has stability across motion directions.The purpose of Study 2 is also based on motion capture system to explore whether the clues of co-actor's task can cause the co-presentation effect in asymmetric joint action task without visual observation(cannot see each other).Experiment 3a aims to explore whether the task clue prompts on co-presentation in inter-individuals.21 pairs of subjects are selected to complete the task under 2(clue:yes,no)×2(obstacle:yes,no)within-subject design.We find that after the clues appearing,the stimulus features of co-actor influence the movements peak height of the actor compared to no clues condition.Experiment 3b,based on experiment 3a,changes the motion direction of the actor to examine the stability of the co-representation effect which is based on abstract clues.The results of 18 pairs subjects show that the effect has stability across motion directions.The results of Study 2 suggest that the task clues could cause the task co-presentation between actor and co-actor,and it also has stability across motion directions.The purpose of Study 3 is by hyperscanning which based on fNIRS,to explore the neural basis of the co-representation effect in asymmetric joint action task.Experiment 4 aims to investigate the neural basis of co-representation in the condition of visual observation.While experiment 5 focus to describe the neural basis of co-representation caused by the clues of co-actor's task.The results of actor's single-brain activation show that under the visual observation condition,the activation level of actor's temporoparietal junction is higher when an obstacle appears in co-actor's task than when no obstacle appears in co-actor's task.And in the condition with clue,we find similar results.The analysis of 18 pairs double-brains activation shows that neural synchronous activity between the inter-individual brain regions tied to motor planning(premotor and supplementary motor cortex of actor as well as the dorsolateral prefrontal cortex of co-actor)under vision observation condition and clue condition is enhanced,compared to no visual(or no clue)condition.Apart from that,the neural synchronous activity between the inferior frontal gyrus of actor and the temporoparietal junction of co-actor is enhanced under the visual observation condition than the clue condition.These results of above experiments indicate that temporoparietal junction of actor is related to the co-presentation effect in asymmetric joint action task.The synchronic enhancement of neural activity in the brain regions associated with motor planning may be the neural basis for the co-representation effect between actors in asymmetric joint action task.The neural activity synchronic enhancement between neural areas related to motion observation of actor and areas related to motor execution of co-actor is unique to the co-representation effect which is based on visual observation.Under the experimental conditions of this paper,the following conclusions can be drawn:1.In the asymmetric joint action task,co-actor influences the actor's action performance.This co-presentation effect caused by observation has stability across motion directions.Actor represent the stimulus features of co-actor's task is the reason of the co-presentation effect.2.The clues of co-actor's task can also induce the co-presentation effect under the asymmetric joint action task without visual observation.This effect also has stability across motion directions.3.Temporoparietal junction of actor is related to the co-presentation effect in asymmetric joint action task.The synchronic enhancement of neural activity in the brain regions associated with motor planning may be the neural basis for the co-representation effect between actors in asymmetric joint action task.The neural activity synchronic enhancement between neural areas related to motion observation of actor and areas related to motor execution of co-actor is unique to the co-representation effect which is based on visual observation.