Description of the amygdala and hippocampus has been performed using manual tracing by expert raters, due to concerns regarding validity of existing automated methods for quantification of these structures, and is not yet completed for the longitudinal sample. In a previous report from a cross-sectional sample subset of the NIMH sample, amygdala volume increased significantly during adolescence only in males and hippocampal volume increased significantly only in females (Giedd et al. 1996). This pattern of gender-specific maturational volumetric changes is consistent with nonhuman primate studies indicating a relatively high number of androgen receptors in the amygdala (Clark et al. 1988) and a relatively higher number of estrogen receptors in the hippocampus (Morse et al. 1986).
