The involvement of parietal and prefrontal areas in human imitation revealed by fMRI adaptation

The perception and imitation of human movement requires that the brain integrates information about the goal of the movement and the kinematics that define it. Neuroimaging and neurophysiological studies implicate the ventral premotor cortex (Ba44) in the processing of action goals while the role of the parietal cortex is not entirely clear. The aim of this series of experiments was to disentangle the role of both prefrontal and parietal areas in the imitation of human movement. To this end we used human arm movements presented as point light displays. The movements were manipulated parametrically to produce morphs that differed from each other in their kinematics. Three different action types -throwing, lifting and knocking movements- and their morphs were utilised for this study. We used a rapid event related fMRI adaptation paradigm, in which fMRI responses to two sequentially repeated stimuli are lower than for different stimuli. We begun by functionally localising the brain areas involved in the imitation of human movement. We then looked at the MR signal under the different experimental conditions during the event related scans. In a first experiment we investigated the basic adaptation effect; identical movements both in their action goals and kinematics were tested against movements that were different in both their goals and kinematics. Preliminary evidence suggests that prefrontal and parietal areas show adaptation under those different experimental conditions. Future experiments will test whether the parietal areas respond to different kinematics even when the goal of the movement is the same, by using the kinematics morphs.