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Abstract:
The neuronal system involved in action understanding and imitation, involves the ventral premotor cortex (Ba44), parietal areas and the Superior Temporal Sulcus (STS). Neuroimaging and neurophysiological studies implicate the ventral premotor cortex in the processing of action goals while the function of the remaining areas is largely unknown. The present study investigated whether the goal and the kinematics of the movement are differentially processed within these cortical areas. We used an event-related fMRI adaptation paradigm, in which fMRI responses to two sequentially repeated stimuli are lower than for different stimuli. Using kinematics morphs (Hill Pollick, 2000) we tested the hypothesis that the premotor cortex in humans processes information about the goal of an action while parietal regions code for the kinematics of the movement. Four different action types and their kinematics morphs were used for the experiments. We functionally localised the brain areas involved in action understanding and imitation. We then tested for fMRI responses in the different experimental conditions during the event related scans. In the first series of experiments we showed that the premotor cortex represents the goal of the movements independent of their kinematics. Adaptation effects were observed across changes in the movement kinematics in the premotor cortex but not in parietal regions. These results suggest that the premotor cortex represents the goal of movements independent of their kinematics, while parietal regions encode information about the movement kinematics. Surprisingly, adaptation effects in hMT+/V5 and STS were similar to these in the premotor cortex. No differences across conditions were observed in early visual areas (i.e. V1). Subsequent experiments tested fMRI responses when the kinematics of the action remained the same while the goal of the action changed.
