High-pass-filtered checkerboard images selectively activate PPA.

(A and B) Examples of low SF (A) and high SF (B) checkerboards. In the actual experiment, an array of 6×6 checks was used, and the phase of the stimulus was systematically varied (see Materials and Methods for further details). The border around the stimuli is for illustration purposes only. (C and D) The FFTs of low SF (C) and high SF (D) checkerboards. The color map represents the FFT magnitude in Fourier space (see Figure 1A for more details about FFT maps). (E) The comparison between faces and places (an independent localizer scan) showed the classical areas FFA and PPA in the averaged map of four human subjects. The group-averaged activity map is displayed on a flattened view of the right occipito-temporal cortex. (F) The comparison of activity between high SF (yellow/red) and low SF (cyan/blue) checkerboards revealed a high SF bias within PPA. If anything, the opposite bias was found in parts of FFA. The maps are significant at the threshold of p<10⁻².