The processing of emotional stimuli does not appear to be automatic

Behavioral and imaging studies have suggested that the visual processing of facial expression occurs not only automatically but could even take place without conscious awareness. In a recent study (PNAS, 2002), we tested the alternative possibility, namely, that the neural processing of stimuli with emotional content is not automatic and instead requires some degree of attention, similar to the processing of neutral stimuli. We measured fMRI responses evoked by pictures of faces with fearful, happy, or neutral expressions when attention was focused on them (attended condition), and compared the responses evoked by the same stimuli when attention was directed to a difficult peripheral task (unattended condition). In designing a competing task, we chose one that was sufficiently demanding to exhaust all attentional resources on that task and leave little or none available to focus on the faces, even though they were viewed foveally. We found that, for all brain regions that responded to faces, an increased response to emotional stimuli was observed only in the attended condition. Thus, responses to emotional stimuli, including in the amygdala, the orbitofrontal cortex, and ventral visual processing areas, are not automatic and instead require attention.

More recently, we have started to investigate the role of “attentional load” on the processing of unattended emotional faces. Consistent with the results discussed above, differential responses in the amygdala were only observed under low-load conditions, but not during intermediate- and high-load conditions (Neuroimage, 2005).