The early visual encoding of a face (N170) is viewpoint-dependent: a parametric ERP-adaptation study

Abstract

Visual representations of faces are extracted shortly after 100 ms in the human brain, leading to an occipito-temporal cortex N170 event-related potential (ERP). To understand the nature of this early visual representation, a full-front adapting face preceded a different or identical target face identity. The target face varied parametrically in head orientation from the adapting face (0-90°, 15° steps). The N170 elicited by the target face increased progressively from 0° up to 30° head orientation, with no further increase until 90°. The N170 decreased for repeated face identities, this effect being stable between 0° and 30° changes of viewpoint, and no effect beyond that angle. These observations suggest that a face is encoded in a view-dependent manner, being matched to either a full-front or a profile face view. Yet, individual face representations activated as early as the peak of the N170 generalize partially across views.

Keywords: Adaptation; Event-related potential; Face perception; Head orientation; Identity; N170; Viewpoint dependence.