The neural correlates of covert recognition of familiar faces

Abstract

It is well established that our brains are highly sensitive to face. We can easily recognize a face even it is seriously degraded. Specially, our brains can even make a response to a face of which we can not overtly be aware. A good many of studies have reported such covert or unconscious face recognition. However, little is known about the neural correlates underlying such face processing. Patients with acquired prosopagnosia may be a good mode for the investigation of the neural mechanism of covert face processing, because they are unable to consciously identify the faces with which they were very familiar previously after the onset of their diseases. Here, we use fMRI methodology to compare the brain activities between a prosopagnosic patient and normal controls when they viewed famous face and unfamiliar face stimuli. We found that the FFA of the patient was activated only by famous faces relative to common objects stimuli. In contrast, the FFA of the normal controls was activated by both famous faces and unfamiliar faces. Further, when comparing the fMRI activities of famous face to those of unfamiliar faces, the normal controls showed enhanced activation in the lateral prefrontal cortex and right posterior parietal lobule (Figure 1). Such brain regions have been suggested to be involved in the overt processing of face identity information. In contrast, using the same contrast as the normal controls, the patient did not show enhanced activities in such regions, but instead presented greater activation in the medial prefrontal cortices (Figure 2). Our findings suggested that the FFA may be involved in both overt and covert face processing, and the patient' s impairment in overt recognition of famous faces is likely to be due to the absent activation of the lateral prefrontal cortices and right posterior parietal lobule.

Meeting abstract presented at VSS 2013