Abstract
The N170 is a negative-going visually evoked potential that is particularly robust for faces. However, it is unclear whether this component reflects the detection of a face or the discrimination of individual faces. Most studies that directly compared N170s across individual faces have failed to find differences (e.g., Bentin & Deouell, 2000; Eimer, 2000), yet one recent study reported a larger N170 for morphed faces perceived as distinct from one another (Jacques & Rossion, 2006). Furthermore, although eyes seem particularly important for identity discrimination (e.g., Gold et al., 1999, 2004; Gosselin & Schyns 2001; Sekuler et al., 2004), studies examining the importance of the eye-region in driving the N170 have yielded conflicting results (e.g., Bentin et al., 1996; Eimer et al., 1998; Schyns et al., 2003; Itier et al., 2006).
The current study examined whether the N170 is linked to performance in a 2-face discrimination task. Across conditions, faces were degraded to include different regions of the face, while equating the total information available for discrimination. Faces containing the most informative pixels consisted of pixels primarily from the eye region; faces containing moderately- and least-informative pixels contained pixels distributed widely throughout the face, but not near the eyes. Consistent with earlier behavioural results (Gaspar et al., VSS 2003), discrimination accuracy was lowest in the least-informative pixel condition, even though stimuli in that condition had the greatest resemblance to normal faces. However, the N170 for full faces most closely resembled that for the least-informative pixel condition. Thus, our results show a clear dissociation between the N170 and discrimination performance.
This research was supported by NSERC operating grants 105494 & 42133 and the Canada Research Chairs Programme (ABS & PJB), a CIHR Fellowship (GAR), and an NSERC PGS-D Fellowship (JSH).