The MRI data were obtained using a 3-T scanner (Intera; Phillips Medical Systems NA, Bothell, Washington) at the Symbion Clinical Research Imaging Centre, Prince of Wales Medical Research Institute, Sydney. A 3-dimensional volumetric spoiled gradient–recalled echo sequence generated 180 contiguous coronal slices. The imaging parameters were as follows: echo time, 2.9 milliseconds; repetition time, 6.4 milliseconds; flip angle, 8°; matrix size, 256 × 256; and 1-mm3 voxels. Hippocampal, amygdala, whole brain, and intracranial volumes were measured using established reliable protocols28- 31 and were delineated by a trained rater (S.W.) masked to group information. Specifically, the hippocampal boundaries were as follows: posterior, the slice with the greatest length of continuous fornix; medial, the open end of the hippocampal fissure posteriorly, the uncal fissure in the hippocampal body, and the medial aspect of the ambient gyrus anteriorly; lateral, the temporal horn of the lateral ventricle; inferior, the white matter inferior to the hippocampus; superior, the superior border of the hippocampus; and anterior, the alveus was used to differentiate the hippocampal head from the amygdala. The anterior border was the most difficult to identify consistently and was aided by moving between slices before and after the index slice. The amygdala boundaries were as follows: posterior, the appearance of amygdala gray matter above the temporal horn; superolateral, the thin strip of white matter that separates the amygdala from the claustrum and the tail of the caudate; medial, the angular bundle, which separates the amygdala from the entorhinal cortex; superomedial, the semilunar gyrus; inferior, the hippocampus; inferolateral, the temporal lobe white matter and the extension of the temporal horn; and anterior, the slice anterior to the appearance of the optic chiasm. Whole brain volumes were estimated using the Brain Extraction Tool method32 to separate brain from nonbrain tissue. After brain/nonbrain segmentation, each voxel was classified into gray matter, white matter, or cerebrospinal fluid using FAST Model statistical software.33 Only gray and white matter were used in the estimate of whole brain volumes. The intracranial cavity was delineated from a sagittal reformat of the original 3-dimensional data set. The major anatomical boundary was the dura mater below the inner table, which was generally visible as a white line. Where the dura mater was not visible, the cerebral contour was outlined. Other landmarks included the undersurfaces of the frontal lobes, the dorsum sellae, the clivus, and the posterior arch of the craniovertebral junction.