Moving mirrors: a high-density EEG study investigating the effect of camera movements on motor cortex activation during action observation.

Action execution-perception links (mirror mechanism) have been repeatedly suggested to play crucial roles in social cognition. Remarkably, the designs of most studies exploring this topic so far excluded even the simplest traces of social interaction, such as a movement of the observer toward another individual. This study introduces a new design by investigating the effects of camera movements, possibly simulating the observer's own approaching movement toward the scene. We conducted a combined high-density EEG and behavioral study investigating motor cortex activation during action observation measured by event-related desynchronization and resynchronization (ERD/ERS) of the mu rhythm. Stimuli were videos showing a goal-related hand action filmed while using the camera in four different ways: filming from a fixed position, zooming in on the scene, approaching the scene by means of a dolly, and approaching the scene by means of a steadycam. Results demonstrated a consistently stronger ERD of the mu rhythm for videos that were filmed while approaching the scene with a steadycam. Furthermore, videos in which the zoom was applied reliably demonstrated a stronger rebound. A rating task showed that videos in which the camera approached the scene were felt as more involving and the steadycam was most able to produce a visual experience close to the one of a human approaching the scene. These results suggest that filming technique predicts time course specifics of ERD/ERS during action observation with only videos simulating the natural vision of a walking human observer eliciting a stronger ERD than videos filmed from a fixed position. This demonstrates the utility of ecologically designed studies for exploring social cognition.