Biological Psychology 59 (2002) 171 – 186 Discrimination of emotional facial expressions in a visual oddball task: an ERP study S. Campanella a, *, C. Gaspard a , D. Debatisse b , R. Bruyer a , M. Crommelinck b , J.-M. Guerit b a Unite ´ de Neurosciences Cognities (NESC), Faculte de Psychologie, Uniersite ´ Catholique de Louain, Place du Cardinal Mercier 10, B-1348 Louain -la -Neue, Belgium b Laboratoire de Neurophysiologie (NEFY), Uniersite ´ Catholique de Louain, Brussels, Belgium Received 26 June 2001; accepted 4 January 2002 Abstract Several ERP studies have shown an orienting complex, the N2/P3a, associated to the detection of stimulus novelty. Its role consists in preparing the organism to process and react to biologically prepotent stimuli. Whether this N2/P3a: (1) could be obtained with complex visual stimuli, such as with emotional facial expressions; and (2) could take part in a complex discrimination process has yet to be determined. To investigate this issue, event-related potentials were recorded in response to repetitions of a particular facial expression (e.g. sadness) and in response to two different deviant (rare) stimuli, one depicting the same emotion as the frequent stimulus, while the other depicted a different facial expression (e.g. fear). As expected, deviant stimuli evoked an N2/P3a complex of larger amplitude than frequent stimuli. But more interestingly, when the deviant stimulus depicted the same emotion as the frequent stimulus the N2/P3a was delayed compared to the response elicited by the different-emotion deviant. The N2/P3a was thus implicated in the detection of physical facial changes, with a higher sensitivity to changes related to a new different emotional content, perhaps leading to faster adaptive reactions. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Event-related potential; Oddball; Facial expressions; Categorical perception; N2/P3a; Latency www.elsevier.com/locate/biopsycho * Corresponding author. Tel.: +32-10-473808; fax: +32-10-473774. E-mail address: salvatore.campanella@psp.ucl.ac.be (S. Campanella). 0301-0511/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0301-0511(02)00005-4