Conscious perception of fear in faces: Insights from high-density EEG and perceptual awareness scale with threshold stimuli.

Visual awareness of fear expressed on a face is associated with a frontal brain response occurring 150–300 milliseconds after seeing the face, beyond the earlier face-sensitive N170 component. Using high-density EEG and a staircase procedure to individually calibrate perceptual thresholds, the study compared brain activity when participants were aware versus unaware of the emotion on otherwise identical faces. A data-driven cluster analysis showed that awareness of fear specifically modulated a frontal event-related potential in that time window. The findings are discussed in relation to current theories of visual consciousness and proposed neural correlates of consciousness.

Study at a glance

Abstract

Contrary to the extensive research on processing subliminal and/or unattended emotional facial expressions, only a minority of studies have investigated the neural correlates of consciousness (NCCs) of emotions conveyed by faces. In the present high-density electroencephalography (EEG) study, we first employed a staircase procedure to identify each participant's perceptual threshold of the emotion expressed by the face and then compared the EEG signals elicited in trials where the participants were aware with the activity elicited in trials where participants were unaware of the emotions expressed by these, otherwise identical, faces. Drawing on existing knowledge of the neural mechanisms of face processing and NCCs, we hypothesized that activity in frontal electrodes would be modulated in relation to participants' awareness of facial emotional content. More specifically, we hypothesized that the NCC of fear seen on someone else's face could be detected as a modulation of a later and more anterior (i.e., at frontal sites) event-related potential (ERP) than the face-sensitive N170. By adopting a data-driven approach and cluster-based statistics to the analysis of EEG signals, the results were clear-cut in showing that visual awareness of fear was associated with the modulation of a frontal ERP component in a 150-300 msec interval. These insights are dissected and contextualized in relation to prevailing theories of visual consciousness and their proposed NCC benchmarks.