Creating and Presenting Real and Artificial Visual Stimuli for the Neurophysiological Investigation of the Observation/Execution Matching System Marco Agus, Fabio Bettio, and Enrico Gobbetti CRS4 Center for Advanced Studies, Research, and Development in Sardinia VI Strada Ovest, Z.I. Macchiareddu, C.P. 94, I-09010 Uta (CA), Italy E-mail: {magus,fabio,gobbetti}@crs4.it, WWW: http:://www.crs4.it/vvr Abstract. Recent neurophysiological experiments have shown that the visual stimuli that trigger a particular kind of neurons located in the ventral premo- tor cortex of monkeys and humans are very selective. These mirror neurons are activated when the hand of another individual interacts with an objects but are not activated when the actions, identical in purpose, are made by manipulated mechanical tools. A Human Frontiers Science Program project is investigating which are the parameters of the external stimuli that mirror neurons visually ex- tract and match on their movement related activity. The planned neurophysiolog- ical experiments will require the presentation of digital stimuli of different kinds, including video sequences showing meaningful actions made by human hands, synthetic reproductions of the same actions made by realistic virtual hands, as well as variations of the same actions by controlled modifications of hand ge- ometry and/or action kinematics. This paper presents the specialized animation system we have developed for the project. 1 Introduction In spite of its fundamental role for human and animal behavior, very little is known on how individuals recognize actions performed by others. It has been often proposed that to recognize motor actions a common code should exist between the observed events and an internally produced motor activity. Neurophysiological evidence in favor of this putative common code was, however, until recently lacking. A possible breakthrough in this field was the discovery in the monkey of a set of neurons with surprising properties. These neurons, that are located in the ventral premotor cortex, discharge both when the monkey makes a hand action directed towards an object and when it observes another individual making a similar action (“mirror neurons”). In many instances the similarity between the active action and the observed action that activates the neurons is very tight. An action made by others is represented, therefore, in the premotor cortex. If one admits that an individual, when making an action, may predict its outcome, it appears likely that he/she will recognize an action made by others because it evokes a discharge in those same neurons that fire when he/she makes the identical action.