(A) The bar plot shows the mean curvature value (see text for formula) for HM, VM, Fov, and Per vertices in the entire visual cortex, averaged across all monkey and all human data. (B) The bar plot shows the mean curvature value for HM and VM vertices in V1, V2, and ‘non-V1/V2’ (nV1/V2) visual cortex, averaged across all monkey and all human data. The error bars indicate one standard error of the mean, as obtained by averaging across hemispheres.

The maps show the relative fMRI activation for horizontal versus vertical meridian. The activation maps are displayed on a lateral view of folded (top) and inflated (bottom) visual cortex in a macaque monkey (left), and on a medial view of folded (top) and inflated (bottom) visual cortex in a human subject (right). The sulci are indicated as follows: Cal, calcarine; eCal, external calcarine; LuS, lunate; IOS, inferior occipital. The color scale bar indicates the P value, in logarithmic format.

The right panels show the relative fMRI activation for horizontal meridian (yellow/red) versus vertical meridian (cyan/blue), displayed on a flattened view of visual cortex from one representative hemisphere in monkeys (top) and humans (bottom). To flatten the cortical surface, the inflated brain was cut along the calcarine fissure. Gyral and sulcal cortical folds are shown in light and dark gray, respectively. The scatter plots in the left panels show the relationship between meridian representations and cortical folding in the same hemispheres as shown in the right panels. Each data-point (‘+’) in the scatter plots corresponds to a vertex in the cortical surface, as reconstructed with FreeSurfer. For each vertex, the curvature value (X-axis) and the logarithmic P value for ‘HM vs. VM’ contrast (Y-axis) were extracted; then these values were plotted for all vertices of the entire cortex. The curvature values were based on FreeSurfer’s curv file (sulci have positive values, and gyri have negative values). Vertices with positive P values (HM > VM) are yellow, and vertices with negative P values (HM < VM) are cyan.