Statistical parametric map of grey matter volume associated with a measure of crowding [spacing (shapes/numbers)]. The SPM is displayed on axial (A), coronal (B) and sagittal (C) sections of the custom template in MNI space: the right hemisphere is shown on the right in coronal and axial sections. When restricting analysis to a prespecified region of interest (outlined in blue), there was an association between a greater degree of crowding and lower grey matter volume in the collateral sulcus (FWE corrected: P < 0.05; peak t = 6.61, location: x = 30 y = −58 z = −8): the colour-map indicates t-values for this association.