Differential early ERPs to fearful versus neutral facial expressions: a response to the salience of the eyes?

Several event-related potential (ERP) studies have demonstrated a negative shift in ERPs for fearful relative to neutral facial expressions approximately 170-300 ms post-stimulus over occipital-temporal scalp. In the present study, three experiments were conducted to examine the importance of the eye region for this ERP differentiation. ERPs and behavioral discrimination responses were measured to fearful and neutral expressions when only the eye region of the expression was visible (the eyes and eyebrows or the eyes alone) and when the eye region (the eyes and eyebrows or the eyes alone) was covered by dark glasses. The results showed a negative shift in ERPs for fearful relative to neutral expressions over lateral temporal sites, starting approximately 160-210 ms post-stimulus. The visibility of the eye region but not the eyes per se was critical for these ERP differences to occur. There were, however, indications that information in the eyes is also coded and used in the categorization of facial expressions.