Unconscious processing of emotional content in hybrid faces

Abstract

Seventeen participants were shown hybrid faces in an event-related design while undergoing functional magnetic resonance imaging (fMRI), we investigated the hypothesis that unconscious processing of emotion can take place, and that this process is driven by information the low spatial frequency spectrum. Furthermore we investigated the amygdala’s role in a hypothesized subcortical pathway for emotional processing. The hybrid images either contained implicit emotional information in the low spatial frequency range (1-7 cycles/image) and a neutral expression in the rest of the bandwidth, or hybrids containing an implicit neutral expression in low spatial frequency range and an explicit emotional expression in the rest of the bandwidth. We found that manipulating spatial frequency information did not lead to significant increase in amygdala activity for single filtered or hybrid images with emotional content in the low spatial frequency range. Possible issues with ¬ non-independent ROI-analysis are discussed and how it may lead to inflated spurious results in previous studies. The behavioral data do however show that hybrid images with implicit emotional content were rated as significantly more unfriendly/friendly when compared to neutral broadband images. The behavioral data does support the idea that the low frequency information can influence a rather complex social judgment, but are not in line with the fMRI data. Too many conclusions could not be drawn due to the substantial inter-subject variability in the fMRI data.