Abstract
The N170 component to a face stimulus presented in the periphery is strongly reduced when another face is present at the fovea (Jacques & Rossion, NeuroReport, 2004). A similar but smaller reduction is observed for fixated faces in the context of peripheral faces (Jacques & Rossion, JOV, in press). Together with the fact that the N170 decreases with eccentricity (Rousselet et al., JOV 2005), these results suggest the existence of a visual competition modulated by a foveal bias, the N170 amplitude being mostly driven by the stimulus at the fovea. Here we clarify this question in an experiment in which a face or a scrambled-face was presented at the fovea together with 2 peripheral faces or scrambled-faces centered at 5 degrees to the left and right of the fixation point. As hypothesized, the N170 amplitude was mostly driven by the stimulus at the fovea.
This was particularly true for a foveal face stimulus, in which case there was no increase associated with peripheral faces at left and temporal sites, and a small increase at occipital right hemisphere sites. The presence of a scrambled-face at the fovea, presented simultaneously with peripheral faces, tended to drive the signal toward the lower N170 response to a scrambled-face alone. Yet, there was still an increase due to faces presented in the periphery. This effect had a bilateral occipital-temporal topography.
These results suggest that foveal stimuli have a strong competitive advantage over stimuli in the periphery, an effect that is even stronger for faces.
GAR is supported by a CIHR fellowship grant. BR and CJ are supported by the National fundation for scientific research (FNRS)