Structural Encoding and Identification in Face Processing: Erp Evidence for Separate Mechanisms

Abstract

The present study had two aims. The first aim was to explore the possible top-down effect of facerecognition and/or face-identification processes on the formation of structural representation of faces, as indexed by the N170 ERP component. The second aim was to examine possible ERP manifestations of face identification processes as an initial step for assessing their time course and functional neuroanatomy. Identical N170 potentials were elicited by famous and unfamiliar faces in Experiment 1, when both were irrelevant to the task, suggesting that face familiarity does not affect structural encoding processes. Small but significant differences were observed, however, during later-occurring epochs of the ERPs. In Experiment 2 the participants were instructed to count occasionally occurring portraits of famous politicians while rejecting faces of famous people who were not politicians and faces of unfamiliar people. Although an attempt to identify each face was required, no differences were found in the N170 elicited by faces of unfamiliar people and faces of familiar non-politicians. Famous faces, however, elicited a negative potential that was significantly larger than that elicited by unfamiliar faces between about 250 and 500msec from stimulus onset. This negative component was tentatively identified as an N400 analogue elicited by faces. Both the absence of an effect of familiarity on the N170 and the familiarity face-N400 effect were replicated in Experiment 3, in which the participants made speeded button-press responses in each trial, distinguishing among faces of politicians and faces of famous and unfamiliar non-politicians. In addition, ERP components later than the N400 were found to be associated with the speed of the response but not with face familiarity. We concluded that (1) although reflected by the N170, the structural encoding mechanism is not influenced by the face recognition and identification processes, and (2) the negative component modulated by face familiarity is associated with the semantic activity involved in the identification of familiar faces.

ERP Evidence of Atypical Face Processing in Young Children with Autism

“…Reports with adults have suggested the N170 is: (1) affected by repetition (Caharel et al, 2002;Itier & Taylor, 2004;Jemel et al, 2003); (2) not affected by stimulus repetition (e.g., Begleiter, Porjesz & Wang, 1995;Schweinberger. Pfutze & Sommer, 1995;Schweinberger, Pickering, Jentzsch, Burton, & Kaufman 2002); and (3) not affected by familiarity (e.g., Bentin & Deouell, 2000;Eimer, 2000;Rossion et al, 1999). However, a later component, the N250 has been shown to be manipulated by familiarity and repetition (Schweinberger et al, 2002).…”

Multiple cues in social perception: The time course of processing race and facial expression

“…For instance, N200s are larger to pictures of one's own face than to other's faces (Tanaka, Curran, Porterfield, & Collins, 2005), and to famous as compared with unfamiliar faces (Bentin & Deouell, 2000). In the case of expression and race, although automatic vigilance mechanisms make it adaptive to initially devote greater attentional resources to angry faces and faces of racial outgroup members (as reflected in the N100 and P200), individuals with positive or neutral expressions, and those who are racial ingroup members are probably more desirable for greater individuation.…”

Cognitive Neuroscience and Neuropsychology

“…For instance, electrophysiological studies have pinpointed a negative event-related potential (ERP) component peaking between 150 and 190 ms, which is highly sensitive to faces (the N170), distributed maximally over occipito-temporal cortex. Much of this research implicates the N170 in initial structural face encoding [3,4], but finds that it is insensitive to facial identity and familiarity [5] -a dissociation predicted by Bruce and Young's model [2]. Surprisingly, little is known, however, about the neural encoding of social category information.…”

“…Given an a priori hypothesis of N170 involvement in social category encoding and its localization to occipito-temporal sites [3][4][5], we measured mean amplitudes between a poststimulus window of 150-190 ms that were averaged together for left occipito-temporal sites (CP5/P3) and together for right occipito-temporal sites (CP6/P4). The N170 in the left hemisphere did not reliably differ for sex-typical (mean = 0.97 mV) versus sex-atypical (mean = 1.09 mV) faces [t(22) = 0.29, P = 0.78].…”

“…Subsequent firing of this same neuronal population, however, appears to gradually sharpen over time by coming to represent finer facial information, including identity and emotional expression [6]. This initial rough distinction between face and non-face stimuli in macaque temporal cortex likely corresponds with the early face-detection mechanism in humans peaking approximately 100 ms after face presentation [7], which is approximately 70 ms before the structural encoding operations reflected by the N170 [3][4][5]. That the same neuronal population gradually transitions from processing global characteristics (e.g.…”