Nonconscious processing of fearful and neutral faces modulates the N170.

Abstract

Prioritised processing of fearful compared to neutral faces, is reflected in event-related potentials (ERPs), but the extent to which fearful faces enhance ERPs when not consciously perceived remains debated. The N170 component is considered a key marker for nonconscious processing of fearful faces. In this pre-registered study (N = 62), we tested whether the P1, N170, and early posterior negativity (EPN) differentiate between fearful faces, neutral faces, and non-facial control stimuli. Consciousness was manipulated using backward-masked stimuli presented for 17 ms, with masks following immediately or after 200 ms. Participants rated their subjective perception on a perceptual awareness scale in each trial. We found strong evidence for an increased N170 response to nonconscious fearful versus neutral faces and for N170 differences between nonconscious faces and non-facial stimuli. No significant effects were found for P1 or EPN amplitudes in nonconscious conditions, although exploratory analyses suggest a possible P1 difference between faces and non-faces. These findings support that nonconscious emotion and face processing are detectable in early neural responses, albeit much weaker than during conscious perception. Future research should examine the influence of low-level stimulus differences and experimental conditions on these results.