Movement and expression in the development of social cognition

What kind of movement or behavior is involved in neonate imitation? What exactly is the newborn infant doing when it responds to seeing gestures on another person's face? This question is closely related to some other questions, such as whether neonate imitation is possible, and whether it is truly imitation. Piaget, of course, thought that this sort of "invisible imitation" was not possible for infants less than 8-12 months of age.