The action-perception link has also a physiological basis. In the macaque monkey, neurons have been found that fire both during the grasping of objects and during the observation of graspable objects (Rizzolatti and Fadiga, 1998; Murata et al., 1997; Rizzolatti et al., 1988). These neurons have been termed `canonical F5 neurons' (located in the premotor cortex, area F5)1.4. They are specific to the type of goal, for example, to precision grips or power grips, and also to the size of observed objects (which require different grip types). Furthermore, they do not respond to objects out of reach.
This link between action and perception is not only restricted to the direction from vision to premotor neurons; actions can also influence the activation of the visual cortex. On humans, using functional magnetic resonance imaging (a tool to visualize the local energy consumption in the vital brain), Astafiev et al. (2004) could show that the area in the visual cortex that responds to observing body parts of other humans is also active during goal-directed movements of the observer's own limbs.