Abstract
Picture plane inversion of a face image dramatically impairs face recognition. This effect occurs at perceptual encoding, as suggested by the observation of a peak latency delay and amplitude increase of the early face event-related potential (ERP) N170 to inverted compared to upright faces (e.g. Rossion et al., 1999). However, the factors driving this latency and amplitude increase, as well as the relationship between these modulations and behavioral face inversion effects remain unclarified. To address this question, we presented subjects (n=25) with faces at 12 different orientations in 30° steps while recording ERPs. At the N170, parametric changes in face orientation yielded distinct patterns of amplitude and latency modulations. Whereas the entire amplitude modulation of the N170 was observed in the 0° to 90° range with no further increase from 90° to 180°; the latency increase with orientation was mostly observed in the 60° to 180° range. Behavioural performances over the 12 orientations were measured in a same/different matching task. Accuracy and reaction times data followed a sigmoid-like function with modulations mostly observed between 30° and 120°. This pattern of behavioral result closely matches the observed amplitude modulation pattern of the N170, not the latency. These results show for the first time a dissociation between amplitude and latency modulations of the N170 as a result of picture-plane rotation of face images. Moreover they suggest a strong relationship between N170 amplitude increase and the behavioral face inversion effect.
CJ and BR are supported by the Belgian National Foundation for Scientific Research (FNRS)