Early Responses to Nonconscious Fear-Conditioned Faces-An ERP Study

Prioritized processing of emotionally relevant faces compared to neutral faces is reflected in differential event-related potentials (ERPs). However, there is an ongoing debate about the extent to which faces, in general, and fear-conditioned faces, in particular, enhance early ERPs when they are not consciously perceived. Here, we tested whether early ERP components (P1 and N170) differentiate between fear-conditioned (CS+) and non-aversive (CS-) faces presented for 17 ms in a backward-masking design using a sequential Bayesian sampling procedure (N = 40). Consciousness was manipulated by presenting the mask directly (0 ms) or after a delay (200 ms) following the target stimulus. Participants were asked to rate their subjective perception after each trial to differentiate between trials in which they perceived nothing beyond the mask, brief glimpses of anything other than a face, vague impressions of a face, or clear impressions of a face. CS+ as compared to CS- faces led to increased N170 amplitudes in the conscious condition among successfully conditioned participants, but not in the nonconscious condition, while no differential effects were observed for the other ERP components. Thus, the data do not support the assumption that fear-conditioned stimuli are processed nonconsciously in the visual cortex.