رویداد بالقوه مربوط به چهره خاص در انسان مستقل از حالت چهره است

Abstract A face-specific brain EEG potential at approximately 160 ms after stimulus presentation has recently been described by various research groups. Most of these studies analysed this face-specific brain potential using smiling faces as stimuli. In electrophysiological studies, however, differences in amplitude due to the emotional valence of the stimuli were described as early as 100 ms after stimulus presentation. In order to investigate the effect of facial expressions with different emotional content on face-specific brain EEG potentials, event-related potentials (ERPs) to faces with sad, happy and neutral expressions were compared to ERPs elicited with buildings in 16 healthy subjects. A face-specific potential at vertex approximately 160 ms after stimulus presentation has been verified in the present study. No significant differences in latency or amplitude of this component were found for different facial expressions.

. Introduction There is strong evidence from electrophysiological studies for a face-specific event-related potential, which indicates that faces are processed in different brain regions compared to control stimuli. This face-specific brain activity has been reported in the range between 120 (Linkenkaer Hansen et al., 1998) and 175 ms (Boetzel and Grusser, 1989) after the presentation of a face. However, differences in amplitude of brain electrical activity associated with the emotional valence of the stimuli were found as early as 100 ms after stimulus presentation (Pizzagalli et al., 1999). Furthermore, the processing of different facial expressions is supposed to start at approximately 180 ms post-stimulus (Streit et al., 1999). Most studies analysing the face-specific brain potential do not report the expression or emotional content of their face stimuli (Boetzel and Grusser, 1989, Eimer, 1998, Eimer and McCarthy, 1999 and Linkenkaer Hansen et al., 1998) or they used smiling faces only (Boetzel et al., 1995 and Debruille et al., 1998). Therefore, an influence of the emotional valence of the face stimuli on the face-specific brain potential cannot be ruled out. Only one study investigated the influence of different facial expressions and blurred faces on the event-related potentials (ERPs) and did not find any significant differences between conditions (Streit et al., 2000). However, this study failed to include non-facial control stimuli in order to identify the face-specific brain potential. The present study was therefore designed to clarify the issue as to whether the face-specific brain potential is modified by the emotional valence of the face stimuli presented.

Results The amplitudes elicited by faces were significantly larger compared to those evoked by buildings, both for the positive component (P2) between 125 and 238 ms (t=5.53; P<0.001), and for the positive component (P3) between 242 and 500 ms (t=2.50; P<0.05). The grand mean ERPs to faces and buildings at the electrode location Cz are shown in Fig. 1. The P2 component peaked at approximately 162.6 ms in response to faces, and significantly later, at approximately 175.3 ms in response to buildings (t=−2.90; P<0.05). In Fig. 2 the grand mean ERPs at the electrode Cz elicited with happy, sad and neutral faces are shown. The curves and statistical analysis with ANOVA did not reveal any significant differences in amplitude or latency between ERPs elicited with the three different facial expressions. Grand average curves at Cz electrode site for faces and buildings. Fig. 1. Grand average curves at Cz electrode site for faces and buildings. Figure options Grand average curves at Cz electrode site for happy, sad and neutral facial ... Fig. 2. Grand average curves at Cz electrode site for happy, sad and neutral facial expressions.