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56 CHARACTERISTICS OF BRAIN AND BEHAVIORoccur throughout adolescence (Huttenlocher, 1979). Findings from these postmortemstudies went largely ignored in the literature on adolescent behavior. Perhapsthis was because these cellular changes (i.e., myelination and synaptic pruning)were relatively subtle during the adolescent years relative to the dramatic changesearlier in development and it may not have seemed likely that such subtle changesin brain structure could impact behavior on such a gross level.Although we cannot directly measure structural changes at the cellular levelwith MRI, the spatial and temporal patterns of maturational change observed inthe recent imaging studies reflects the patterns observed postmortem. Some clearadvantages of the imaging studies are that larger samples of normally developingindividuals can be studied, they can be studied at multiple time points, and brainand behavioral changes can be correlated. The available imaging technology maynever be adequate or appropriate for assessing such issues as individual culpabilityfor societal extremes in troublesome adolescent behavior, but the developmentalneuroscience community is clearly better poised to address questions regardingrelationships between the brain and behavior than at any previous time.The main focus of this review will be on the exciting new studies of normativebrain development during childhood and adolescence that have been performedwith sophisticated new brain mapping techniques, including cortical pattern matching(CPM). With these studies, we have been able to map structural changes overthe entire cortical surface, advancing our understanding of the timing and localizationof these alterations that occur as part of the sculpting of the human brainat various ages. We will briefly review the earliest quantitative imaging studiesof child and adolescent brain development that used methods designed to calculateregional brain volumes (i.e., volumetrics). These studies continue to be the“gold standard” for assessing changes in brain morphology because they involvemanual designation of cortical and subcortical structures based on visually identifiableanatomical landmarks.More recent techniques rely on state-of-the-art computer algorithms that allowassessment of changes throughout the entire brain at once. Voxel-based morphometry(VBM), for example, involves spatially standardizing brain image volumesthree-dimensionally and assessing gray or white matter change in a completelyautomated way. CPM is also relatively automated but provides some advantageover VBM because sulcal patterns on the cortical surface are delineated, and corticalstructures are matched across subjects based on these landmarks. Both VBMand CPM provide an advantage because they allow three-dimensional visualizationof changes occurring within the brain and at the cortical surface, unbiased byobservable sulcal cortical boundaries necessary for making anatomical delineationsin the volumetric studies. These newer brain mapping studies will be discussedin detail in this chapter, and we will concentrate on changes in the cerebralcortex during childhood and adolescence, because these have been among the mostexciting findings. Because the focus of this collection of work is on adolescent