Abstract
Personally familiar face recognition is fast and extremely accurate despite large variations in viewing conditions, and thus available information. Notwithstanding considerable efforts, the neural correlates of this efficiency remain largely unspecified. Using a novel dynamic visual stimulation technique, we investigated the brain regions involved in perception and recognition of familiar faces encountered repeatedly in real-life (classmates) in an event-related fMRI experiment. Stimulation started with presentation of an average face containing only very low spatial frequency information (LSFI; 1.5 c/f), displayed for ~2500 msec (2TR). Then, incrementally increasing amounts of high spatial frequency information (HSFI; in steps of 1/4 octave per TR; trial duration: 27TR) were provided to progressively and dynamically reveal personally familiar or unfamiliar faces. This slow presentation rate was used to decelerate the recognition process (e.g. James et al., 2000; Kleinschmidt et al., 2002; Sadr & Sinha, 2004; Carlson et al., 2006; Eger et al., 2007), and mimic a coarse-to-fine mode of visual perception (Sergent, 1986). In line with previous findings (Watier & Collin, 2009), familiar face decisions required less HSFI than unfamiliar face decisions. Region of interest analyses within regions comprising the “core system” of face perception (Haxby et al., 2000) revealed that responses in the FFA and STS–not OFA–were modulated by familiarity. Importantly, however, these areas required relatively more HSFI than several regions (face-preferential and non-preferential) identified in a whole brain analysis by contrasting un-/familiar sequences: the amygdala, and other areas of the medial temporal lobe in the right hemisphere (perirhinal cortex, hippocampus), which were not face-preferential. These results emphasize the importance of regions of the medial temporal lobe for familiar face recognition. In particular, they highlight the involvement of the amygdala, which required less HSFI information to categorize faces according to their familiarity, than those regions previously considered to comprise the “core system” of face perception.
MR and BR are supported by the Belgian National Fund for Scientific Research (FNRS).