The papers collected in this issue also make it abundantly clear that many important questions about adolescent brain development remain to be asked and answered. One fundamental issue that desperately needs research attention concerns the role of puberty in adolescent brain development. It has been hypothesized that changes in reward-seeking are linked to the impact of gonadal hormones on brain function (see Dahl & Forbes, this issue), but the extent to which this is the case is uncertain, as is the extent to which these puberty-dependent processes differ between males and females, whose endocrinological environments are obviously very different. (My reading of the literature on sex differences in brain development, reinforced by the contribution to this issue by Lenroot and Giedd, is that the area is littered with inconsistencies and that a coherent story has yet to be told, perhaps because there isn't much of one to tell.) Animal studies suggest that some of the changes in dopaminergic activity are directly attributable to the hormonal changes of puberty, that some are indirectly attributable to them (in that the presence of
