Figure 5.

Schematic illustration of the searchlight induced inflations and spatial inaccuracies. (A) Searchlight shape (down-projection to 2D) with a 5-voxel diameter. The violet shaded voxels are located within the searchlight. (B) No voxels carry class information, except the center voxel featuring the green sphere labeled with the letter “i”: this voxel is the sole voxel carrying class information. As a result of the SLD procedure using searchlight decoding (A), many voxels are being labeled as informative (these voxels are depicted in orange). The inflating effect has previously been termed as “needle in the haystack effect” (Viswanathan et al., 2012). (C) Here, no voxels except the two voxels with the green sphere labeled with “i” carry class information. The information carried by one voxel, however, is sufficiently small so that a searchlight has to include both informative voxels in order to be labeled significant. Hence only the voxels in the middle, where the searchlight contains both informative voxels, are labeled informative, resulting in inaccurate and distorted information maps.