Evidence has accumulated for a mirror system in humans which simulates actions of conspecifics (Wilson amp; Knoblich, 2005). One likely purpose of such a simulation system is to support action prediction. We focused on the time-course of action prediction, investigating whether the prediction of actions involves a real-time simulation process. We motion-captured a number of human actions and rendered them as point light action sequences. In the experiments, we presented brief videos of human actions, followed by an occluder and a static test stimulus. Both the occluder duration (SOA of 100, 400, or 700 ms) and the distance of the test stimulus to the endpoint of the action sequence (corresponding to 100, 400, or 700 ms) were varied independently. Subjects had to judge whether the test stimulus depicted a continuation of the action in the same orientation, or whether the test stimulus was presented in a different orientation in depth as the previous action sequence. Prediction accuracy was best when SOA and distance to the endpoint corresponded, i.e. when the test image was a continuation of the sequence that matched the occluder duration. This pattern of results was destroyed when the sequences and test images were inverted (flipped around the horizontal axis). In this case, performance simply deteriorated with increasing distance to the end of the sequence. Overall, our findings suggest that action prediction involves a real-time simulation process. This process can break down when the actions are presented under viewing conditions for which we have little experience

It is typically assumed that perception for action and object recognition are subserved by functionally and neuroanatomically distinct processing streams in the brain. However, recent evidence challenges this classical view and suggests an interaction between both visual processing streams. While previous studies showed an influence of object perception on action-related tasks, we investigated whether action representations facilitate visual object recognition. In order to address this question, two briefly displayed masked objects were sequentially presented, either affording congruent or incongruent motor interactions. We found superior naming accuracy for object pairs with congruent as compared to incongruent motor interactions (Experiment 1). This action priming effect indicates that action representations can facilitate object recognition. We further investigated the nature of the representations underlying this action priming effect. The effect was absent when the prime stimulus was presented as a word (Experiment 2). Thus, the action priming effect seems to rely on action representations specified by visual object information. Our findings suggest that processes of object-directed action influence object recognition.

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Many studies have shown the involvement of the premotor cortex in action observation, recognizing this region as the neural marker of action simulation (i.e., internal modeling on the basis of the observer's own motor repertoire). So far, however, we have remained unaware of how action simulation differs from more general action representation in terms of premotor activation. The present fMRI experiment is the first to demonstrate how premotor structures contribute to action simulation as opposed to other action-related cognitive tasks, such as maintaining action representations. Using similar stimuli, a prediction condition requiring internal simulation of transiently occluded actions was compared to three different action-related control tasks differing solely in task instructions. Results showed right pre-SMA activation as a correlate of maintaining action representations in general. Moreover, the prediction condition was most efficient in activating the left pre-SMA and left PMd. These results suggest that the conjoint activation of the pre-SMA and PMd reflects a core neural driver of action simulation.