Morphometric analysis was performed on three-dimensional MRI scans of
10 male and 10 female young adults with four principal objectives: (1)
to characterize in vivo volumes of whole brain and substructures, (2)
to explore volumetric symmetry in bilateral structures, (3) to consid
er the extent to which volumetric measures are dimorphic in the male a
nd female brain, and (4) to provide a normal volumetric database for t
he young adult brain. Total brain volumes ranged between 1173 and 1626
cm(3). All bilateral structures were symmetric or nearly symmetric in
volume, with the exception of a slightly larger right neocortex and a
mygdala, and larger left lateral ventricle. Male brains were larger in
volume than female brains, a difference that reached significance for
cerebellar but not for cerebral hemisphere volume. In females, there
was less cerebral white matter while caudate volume was larger than in
the male brains. The proportions of caudate and hippocampus relative
to total cerebral volumes were larger in females than in males. These
four measures accurately predicted gender in 85% of the subjects by di
scriminant analysis. No gender differences were noted in the structura
l symmetry analysis. These results represent the first step in establi
shing a comprehensive database of morphometric parameters, with unexpe
cted findings relative to brain symmetry and sexual dimorphism.