Neural correlates of affective priming effects based on masked facial emotion: an fMRI study

Affective priming refers to the phenomenon that subliminal presentation of facial emotion biases subsequent evaluation of a neutral object in the direction of the prime. The aim of the present study was to specify the neural correlates of evaluative shifts elicited by facial emotion shown below the threshold of conscious perception. We tested the hypotheses whether the amygdala is involved in negative priming, whereas the nucleus accumbens participates in positive priming. In addition, exploratory whole brain correlation analyses were conducted. During 3T fMRI scanning, pictures of sad, happy, and neutral facial expression masked by neutral faces were presented to 110 healthy adults who had to judge valence of masks on a four-point scale. There was evidence for significant negative priming based on sad faces. A correlation was observed between amygdala activation and negative priming. Activation in medial, middle, and superior frontal and middle temporo-occipital areas, and insula was also associated with negative priming. No significant priming based on happy faces was found. However, nucleus accumbens activation to happy faces correlated with the positive priming score. The present findings confirm that the amygdala but also other brain regions, especially the medial frontal cortex, appear involved in automatically elicited negative evaluative shifts.