On the relationship between the execution, perception, and imagination of action.

Humans can perform, perceive, and imagine voluntary movement. Numerous investigations of these abilities have employed variants of goal-directed aiming tasks because the Fitts's law equation reliably captures the mathematical relationship between movement time (MT) and accuracy requirements. The emergence of Fitts's speed-accuracy relationship during movement execution, perception, and imagination has led to the suggestion that these processes rely on common neural codes. This common coding account is based on the notion that the neural codes used to generate an action are tightly bound to the codes that represent the perceptual consequences of that action. It is suggested that during action imagination and perception the bound codes are activated offline through an action simulation. The present study provided a comprehensive testing of this common coding hypothesis by examining the characteristics of the Fitts relationship in movement execution, perception, and imagination within the same individuals. Participants were required to imagine and perceive reciprocal aiming movements with varying accuracy requirements before and after actually executing the movements. Consistent with the common coding account, the Fitts relationship was observed in all conditions. Critically, the slopes of the regression lines across tasks were not different suggesting that the core of the speed-accuracy trade-off was consistent across conditions. In addition, it was found that incidental limb position variability scaled to the amplitude of imagined movements. This motor overflow suggests motor system activation during action imagination. Overall, the results support the hypothesis that action execution, perception, and imagination rely on a common coding system.