Pointwise p-values. We permuted the locations of subjects and reran the GAM model 999 times to estimate the distribution of log odds under the null hypothesis at each point. We define areas of significantly decreased odds ("cold spots") to include all points that rank in the lower 2.5% of the pointwise permutation distribution and areas of elevated odds ("hot spots") to include all points that rank in the upper 2.5% of the pointwise permutation distribution. We superimpose the 2.5% and 97.5% contour lines on the point estimate map. The slightly elevated, but non-significant, region in the lower right corner occurred due to chance.