Actions from within

This paper considers the nature of representations that precede the execution of an action. An analysis of the content of these representations is proposed by using classical tools of cognitive psychology, like introspection and mental chronometry. Their neural vehicle is described in normal subjects with neuroimaging methods and by clinical neuroscience methods like transcranial magnetic stimulation. The contribution of pathological conditions, such as paralysis and amputation, to the description of action representation is discussed. A general framework of motor simulation is proposed as a coherent explanation for the various types of action representation during motor imagery, motor decisions, and action observation. This framework is also used for interpreting the effects of mental training, learning by observation, and the use of neuroprosthetic devices in motorically handicapped people.