Non-conscious processing of emotionally expressive faces has been found in patients with damage to visual brain areas and has been demonstrated experimentally in healthy controls using visual masking procedures. The time at which this subliminal processing occurs is not known. To address this question, a group of healthy participants performed a fearful face detection task in which backward masked fearful and non-fearful faces were presented at durations ranging from 16 to 266 ms. On the basis of the group's behavioural results, high-density event-related potentials were analysed for subliminal, intermediate and supraliminal presentations. Subliminally presented fearful faces were found to produce a stronger posterior negativity at 170 ms (N170) than non-fearful faces. This increase was also observed for intermediate and supraliminal conditions. A later component, the N2 occurring between 260 and 300 ms, was the earliest component related to stimulus detectability, increasing with target duration and differentiating fearful from non-fearful faces at longer durations of presentation. Source localisation performed on the N170 component showed that fear produced a greater activation of extrastriate visual areas, particularly on the right. Whether they are presented subliminally or supraliminally, fearful faces are processed at an early stage in the stream of visual processing, giving rise to enhanced activation of right extrastriate temporal cortex as early as 170 ms post-stimulus onset.
Bibliographical noteFunding Information:
This investigation was supported by the Swiss National Science Foundation grant no. 32-109928 and 325100-118362. The Cartool software used for data analysis ( http://brainmapping.unige.ch/Cartool.htm ) was programmed by Denis Brunet, from the Functional Brain Mapping Laboratory, Geneva, Switzerland, and is supported by the Center for Biomedical Imaging (CIBM) of Geneva and Lausanne.
- Source localisation
ASJC Scopus subject areas
- Neuroscience (all)
- Neuropsychology and Physiological Psychology
- Physiology (medical)