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Mapping Adolescent Brain Change 57psychopathology and the developing brain, we will also discuss some of ourrecent work describing brain morphological abnormalities in children with developmentaldisorders such as fetal alcohol syndrome and attention deficit/hyperactivity disorder. We relate these studies to the normative studies to helpillustrate how we may learn more by integrating normative and disabled populationsthan from either alone.Volumetric Image Analysis FindingsBrain developmental changes in childhood and adolescence have been the focusof numerous volumetric MRI studies in the last decade (Caviness et al., 1996;Courchesne et al., 2000; Giedd et al., 1996a; Giedd et al., 1996b; Giedd et al.,1999; Jernigan et al., 1991; Pfefferbaum et al., 1994; Reiss et al., 1996; Sowell &Jernigan, 1998; Sowell et al., 2002c). Various methods have been used to assessage effects on the volumes of various brain regions and tissues. Researchers haveused tissue segmentation, which involves classification of brain tissue into distinctcategories, to assess age-effects on volumes of gray matter, white matter andcerebrospinal fluid (CSF). Stereotaxic region definition schemes were most characteristicof the earlier studies (Giedd et al., 1996a; Jernigan et al., 1991; Reisset al., 1996), frequently because the image spatial resolution was low (i.e., 4- to5-mm MRI slice thickness), making cortical anatomical landmarks difficult to identifyand follow through successive image slices. In some early volumetric studies,whole brain tissue volumes were assessed for age effects (Caviness et al., 1996;Courchesne et al., 2000), but others employed manual region definition on a sliceby slice basis using cortical anatomical landmarks (where observable) as boundaries(Giedd et al., 1996b; Lange et al., 1997; Sowell & Jernigan, 1998; Sowellet al., 2002c). Finally, automated lobar region definition schemes have been used(Giedd et al., 1999), in which image warping algorithms are used to automatically,three-dimensionally map brain lobe regions from one subject to another.In the earliest report of volumetric brain differences between childhood andyoung adulthood, Jernigan and Tallal (1990) reported that children aged 8 to 10years had significantly more cortical gray matter as a proportion of cerebral sizethan did young adults. These authors followed this preliminary report with a largersample size and stereotaxic subdivision of cortical regions, and found evidencefor an increase in size of the dorsal-most brain region between childhood and youngadulthood (Jernigan et al., 1991), particularly in the frontal lobes. Within the dorsalbrain region, the cortical gray matter appeared to decrease with age while CSFin this region increased. The inferior cortical gray matter volumes did not appearto change across the age range. The authors proposed that their observation of a“thinning” cortex in superior cortical regions could be related to reductions insynaptic density reported earlier in postmortem material (Huttenlocher, 1979).