Searching for face-specific long latency ERPs: a topographic study of effects associated with mismatching features

In a previous study [E. Olivares, M.A. Bobes, E. Aubert, M. Valdes-Sosa, As sociative ERPs effects with memories of artificial faces, Cogn. Brain Res. 2 (1994) 39-48] we reported the presence of a negativity associated with mi smatching features when subjects carried out a face-feature matching task w hilst their evoked potentials were recorded. Since the stimuli used were le arned faces (realistic drawings), for which the subjects possessed no seman tic information or associated verbal labels, the mismatch negativity obtain ed was considered a face-specific N400. In this work we present a new exper iment to study the topographic distribution of these mismatch effects. As i n the above-mentioned study, in each trial the subjects observed previously an incomplete (without the eyes/eyebrows fragment) familiar face, which se rved as a structural context for the face recognition. The face was then co mpleted by grafting either matching (learned) features or mismatching featu res (from another face). In line with neuropsychological studies on prosopa gnosia and electrophysiological findings in humans and non-human primates, we found as one of the most relevant items of data that the most-posterior (principally, left occipital) cortices appear to be a region in which are l ocated the possible neural generators of the negativity associated with the detection of incongruencies in the structure of familiar faces. We also re ported a late positivity, distributed in more anterior regions, which follo ws the mismatch negativity. This complex N-P is interpreted as reflecting a dual process of retrieval and integration of information in memory. (C) 19 99 Elsevier Science B.V. All rights reserved.