Academic journal article Cognitive, Affective and Behavioral Neuroscience

Mapping the Time Course of the Positive Classification Advantage: An ERP Study

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Mapping the Time Course of the Positive Classification Advantage: An ERP Study

Article excerpt

Abstract The aim of the present study was to investigate the time course of the positive advantage in the expression classification of faces by recording event-related potentials (ERPs). Although neutral faces were classified more quickly than either happy or sad faces, a significant positive classification advantage (PCA)-that is, faster classification for happy than for sad faces-was found. For ERP data, as compared with sad faces, happy faces elicited a smaller N170 and a larger posterior N2 component. The P3 was modulated by facial expressions with higher amplitudes and shorter latencies for both happy and neutral stimuli than for sad stimuli, and the reaction times were significantly correlated with the amplitude and latency of the P3. Overall, these data showed robust PCA in expression classification, starting when the stimulus has been recognized as a face revealed by the N170 component.

Keywords Facial expression · Event-related potentials · Positive classification advantage

Introduction

The ability to recognize facial expressions is crucial to adaptive social interaction. Recognizing another's expression of rage or fear, for example, could allow for a rapid response to escape danger. It has been shown that emotionally positive facial express ions are recognized substantially faster than emotionally negative facial expressions-the positive classification advantage (PCA). This effect was evident in happiness recognition, which was faster than recognition for sadness (e.g., Crews & Harrison, 1994; Hanaya, 1992; Leppänen & Hietanen, 2004), anger (e.g., Billings, Harrison, & Alden, 1993; Hugdahl, Iversen, & Johnsen, 1993), disgust (Ducci, 1981; Stalans & Wedding, 1985), and emotional neutrality (Hugdahl et al., 1993; but see Leppänen & Hietanen, 2004). While many of the electrophysiological and neuroimaging studies have investigated emotional face processing, the phenomenon of PCA has received surprisingly little attention. Several previous studies explored the neural mechanism of explicit facial expression categorization by recording eventrelated potentials (ERPs; e.g., Lynn & Salisbury, 2008;fora review, see Eimer & Holmes, 2007) and found that, as compared with neutral faces, fearful faces elicited an enhanced positivity starting at 160 ms poststimulus (Holmes, Kiss, & Eimer, 2005) and that significant differences in N170 amplitude were elicited by facial expressions (Lynn & Salisbury, 2008). Although facial expression classification could modulate the ERP components, the above studies did not involve the phenomenon of PCA: responding whenever the face with a fearful or neutral facial expression presented on the preceding trial was shown again on the current trial (Holmes et al., 2005) or detecting neutral facial expressions from among five emotional expressions (happy, sad, fearful, angry, and disgusted) (Lynn & Salisbury, 2008). Particularly relevant to the present study, recently, recording response selection (onset of the lateralized readiness potential [LRP]) and response execution (LRP onset-response onset) times for positive (happy) and negative (disgusted/angry) faces, Leppänen, Tenhunen, and Hietanen (2003) found shorter response selection times for positive than for negative faces but did not find differences in response execution times, indicating that the PCA occurs primarily at premotoric processing stages. The aim of the present study was to further map the time course of the PCA. To achieve this goal, we examined the sensitivity of a sequence of ERP components to the expression of the face while the participants categorized the stimuli according to their expressions.

The earliest component that has been consistently associated with the faces is the N170, which is a negative ERP occurring between 140 and 180 ms after the stimulus onset at occipito-temporal electrodes and is reliably larger to faces than to other stimulus categories (Bentin, Allison, Puce, Perez, &McCarthy,1996). …

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