Other MRI studies accounting for pubertal development were cross-sectional. A VBM analysis of MRI data in 37 boys and 41 girls, age 10 to 15 years old, showed that smaller total gray matter volumes correlated with higher estradiol levels in girls, notably in prefrontal, parietal, and middle temporal cortices; sex hormone-MRI volume correlations were not forthcoming in the boys, likely because they were, on average, about a year younger than the girls (Peper et al., 2009a). A twin study of 210, 9-year old boys and girls (Peper et al., 2009b) provided strong cross-sectional evidence, based on VBM analysis, for an association between pubertal development in children with secondary sexual characteristic and those without them and the onset of decreasing gray matter in prefrontal and parietal cortical density. Another cross-sectional MRI study in 15 boys and 15 girls with Tanner stage information and circulating hormone levels revealed a complex set of relations involving medial temporal and diencephalic brain structures that suggested a role for sex hormones in influencing the organization of brain development (Neufang et al., 2009).
