The P200 predominantly reflects distance-to-norm in face space whereas the N250 reflects activation of identity-specific representations of known faces

The norm-based face space model (nMDFS) predicts that perceived typicality decreases with distance to the norm. Accordingly, an original face and its corresponding anti-face (deviating in exactly opposite direction from the norm) should inherit equivalent levels of typicality. Similarly, varying distance-to-norm (DTN, in absolute values) should have equivalent effects on typicality for both unfamiliar faces and their anti-faces. Here we reasoned that familiar faces would not follow this rule, due to the special nature of their mental representations. We investigated event-related brain potentials (ERPs) to familiar and unfamiliar faces and their anti-faces with different DTN ( +/- 0.33, +/- 0.66, and +/- 0.99). Across DTN, rated typicality was highest for original familiar faces, whereas all other face stimuli exhibited the expected gradual decrease of typicality with increasing DTN. ERPs showed pronounced DTN effects in the occipitotemporal P200 (190-260 ms), with progressively smaller amplitudes for faces with higher DTN, for all face types. By contrast, prominent effects of familiarity were found for the subsequent N250 (260-400 ms) and a late occipitotemporal negativity (LN, 400-800 ms). A large increase of occipitotemporal negativity was observed for original familiar faces versus their non-recognizable anti-faces. Analogous effects were small or absent for unfamiliar faces versus their anti-faces. These results confirm the N250 and LN as correlates of the processing of the identity of known faces, and show for the first time that the face-sensitive P200 is primarily modulated by DTN of a face in nMDFS.