The complex relationship of cortical morphometry and brain size is highlighted by a recent report in healthy adults relating brain volume to cortical features including thickness, surface area and gyrification (Im et al., 2007a). Consistent with previous reports from postmortem data (Pakkenberg & Gundersen, 1997), they found that increases in gray matter volume were driven primarily by increased surface area rather than cortical thickening. They also found that increased brain size was associated with a marked increase in folding of the cortical surface. There were no sex differences after accounting for differences in total brain size. This is inconsistent with some previous studies which found relatively thicker cortex and greater cortical complexity in females if differences in total brain volume were taken into account (Luders et al., 2004; Luders et al., 2006; Sowell et al., 2006), although the authors speculated that this may have been due to the use of a linear scaling method in the previous studies, which did not completely account for brain size differences. If different brain regions do not scale linearly, it is possible that contrasts
