Motor Imagery - Functional Equivalence of Motor Preparation and Motor Imagery

Functional Equivalence of Motor Preparation and Motor Imagery

Motor imagery has been studied using the classical methods of introspection and mental chronometry. These methods have revealed that motor images retain many of the properties, in terms of temporal regularities, programming rules and biomechanical constraints, which are observed in the corresponding real action when it comes to execution. For instance, in an experiment participants were instructed to walk mentally through gates of a given apparent width positioned at different apparent distances. The gates were presented to the participants with a 3-D visual display (a virtual reality helmet) which involved no calibration with external cues and no possibility for the subject to refer to a known environment. Participants were asked to indicate the time they started walking and the time they passed through the gate. Mental walking time was found to increase with increasing gate distance and decreasing gate width. Thus, it took the participant longer to walk mentally through a narrow gate than to walk through a larger gate placed at the same distance. This finding led neurophysiologists Marc Jeannerod and Jean Decety to propose that there is a similarity in mental states between action simulation and execution. The functional equivalence between action and imagination goes beyond motor movements. For instance similar cortical networks mediate music performance and music imagery in pianists.