To take schizophrenia as an example, structural abnormalities have been reported in many areas of the brain. Abnormalities such as enlarged ventricles and decreased cortical gray matter in the frontal and mediotemporal lobes are found relatively frequently, whereas changes in other brain regions, such as decreased volume of the thalamus and cerebellum, are more variable (Pearlson & Calhoun, 2007; Shenton, Dickey, Frumin, & McCarley, 2001; van Haren, Bakker, & Kahn, 2008). Some of the disparity is likely due to changes in imaging methodology inherent in the technical advances of the past 3 decades. In addition, it has become apparent that most findings are relatively subtle, and that many studies are underpowered (Meda et al., 2008; van Haren et al., 2008). Heterogeneity of patient populations may also be a contributing factor. Clinically, individuals with schizophrenia can have very different presentations, depending on the relative severity of different types of symptoms, and an ongoing debate concerns how best to account for the imperfect correspondence between the clinical diagnostic entity and the underlying neurobiology (Hyman, 2007). An additional complication arises when considering the
