Electrophysiological neural mechanisms for detection, configural analysis and recognition of faces.

Despite ample explorations the nature of neural mechanisms underlying human expertise in face perception is still undetermined. Here we examined the response of two electrophysiological signals, the N170 ERP and induced gamma-band activity (>20 Hz), to face orientation and familiarity across two blocks, one in which the face identity was task-relevant and one in which it was not. N170 amplitude to inverted faces was higher than to upright faces and was not influenced by face familiarity or its task relevancy. In contrast, induced gamma activity was higher for upright than for inverted faces and for familiar than unfamiliar faces. The effect of face inversion was found in lower gamma frequency band (25-50 Hz), whereas familiarity affected amplitudes in higher gamma frequency band (50-70 Hz). For gamma, the relevance of face identity to the task modulated both inversion and familiarity effects. These findings pinpoint three functionally dissociated neural mechanisms involved in face processing, namely, detection, configural analysis, and recognition.