Neural representation for the perception of the intentionality of actions

A novel population of cells is described, located in the anterior part of t he superior temporal sulcus (STSa, sometimes called STPa) of the temporal l obe in the macaque monkey. These cells respond selectively to the sight of reaching but only when the agent performing the action is seen to be attend ing to the target position of the reaching. We describe how such conditiona l selectivity can be generated from the properties of distinct cell populat ions within STSa. One cell population responds selectively to faces, eye ga ze, and body posture, and we argue that subsets of these cells code for the direction of attention of others. A second cell population is selectively responsive to limb movement in certain directions (e.g., responding to an a rm movement to the left but not to an equivalent leg movement or vice versa ). The responses of a subset of cells sensitive to limb movement are modula ted by the direction of attention (indicated by head and body posture of th e agent performing the action). We conclude that this combined analysis of direction of attention and body movements supports the detection of intenti onal actions. (C) 2000 Academic Press.