Repetitive transcranial magnetic stimulation reveals a role for the left inferior parietal lobule in matching observed kinematics during imitation

Abstract

Apraxia (a disorder of complex movement) suggests that the left inferior parietal lobule plays a role in kinematic or spatial aspects of imitation, which may be particularly important for meaningless (i.e., unfamiliar intransitive) actions. Mirror neuron theories indicate that the inferior parietal lobule is part of a frontoparietal system that can support imitation by linking observed and stored actions through visuomotor matching, and have less to say about different subregions of the left inferior parietal lobule, or how different types of action (i.e., meaningful or meaningless) are processed for imitation. We used repetitive transcranial magnetic stimulation (rTMS) to bridge this gap and better understand the roles of the left supramarginal gyrus and left angular gyrus in imitation. We also examined if these areas are differentially involved in meaningful and meaningless action imitation. We applied rTMS over the left supramarginal gyrus, left angular gyrus, or during a no-rTMS baseline condition, then asked participants to imitate a confederate’s actions whilst the arm and hand movements of both individuals were motion-tracked. rTMS over both the left supramarginal gyrus and the left angular gyrus reduced the velocity of participants' finger movements relative to the actor during imitation of finger gestures, regardless of action meaning. Our results support recent claims in apraxia and confirm a role for the left inferior parietal lobule in kinematic processing during gesture imitation, regardless of action meaning