Location of NIRS probes and channels (a) and Fixation pattern maps and topographies for changes in oxyHb levels in one representative subject (b).

<p>(a) Five emission and four detector probes (gray dots) were arranged in a 3×3 square lattice and the three lowest probes were aligned between Fp1/Fp2 and T3/T4 (blue dots). The mid probe of the three was placed around F7/F8 (international 10/20 system). We obtained cortical responses from a total of 12 channels (red dots) in each hemisphere. Numbers in red dots show channel numbers, i.e. 1 means Ch. 1. (b) Hemodynamic activities in the right hemisphere, especially the areas corresponding with inferior frontal gyrus, were higher in the self-face condition compared with other conditions, but fixation patterns were similar among all conditions. Each line presents a condition: the upper line shows the self-face condition, the middle line shows the familiar face condition, and the lowest line shows the unfamiliar face condition. The left column shows fixation maps and the other two columns show hemodynamic changes, the middle column for the right hemisphere and right column for the left hemisphere. A two-dimensional Gaussian distribution was applied to each of the fixation maps created. The center of this Gaussian distribution is the fixation location and its width is set to 1° of visual angle: the height of the Gaussian is weighted by the proportion of dwell time on each area. Both subjects of self- and familiar facial images have given written informed consents (as outlined in the PLoS consent form) to publication of their picture. Unfamiliar facial image was artificially created (nonexistent person).