Neural basis for the subliminal affective priming

A study using event related fMRI

Abstract

The affective primacy hypothesis asserts that positive and negative affective reactions can be evoked with minimal stimulus input. This phenomenon has been tested using subliminal affective priming technique, however, these techniques are not robust enough and have not been fully explored. The aim of this study was to clarify existence of the affective primacy and the underlying mechanism by a neuroimaging method using event related functional magnetic resonance imaging (fMRI). Fourteen participants were scanned during a task in which they evaluated presented facial expressions of "anger, " "neutral, " or "happiness." Target stimuli were faces expressing weak and ambiguous anger expressions, which were presented just after a presentation of either (1) faces with strong anger expressions as affective stimuli, neutral faces, or a non-face object; or (2) flash as a control stimuli of 35ms duration. Processing of facial expressions in each condition commonly increased regional blood oxygenation level-dependent (BOLD) activity in the bilateral inferior frontal gyrus and left anterior cingulate gyrus. We identified the anterior part of anterior cingulate gyrus showed significant activation in the anger prime condition compared with the other three prime conditions. This suggests that the affective priming effect engendered especially in the anterior cingulate cortex. This suggests that a part of the neurophysiological substrates that underlies the subliminal affective priming has been identified.