Life after birth: the influence of steroid hormones on cerebral structure and function is not fixed prenatally.

Bryden, McManus, and Bulman-Fleming conclude that available empirical evidence does not support the Geschwind-Behan-Galaburda model of cerebral lateralization. One of the central assumptions of the model is that fetal testosterone plays a determinant role in the development of anomalous specialization and is associated with various behavioral, cognitive, and immunological disorders. The influence of testosterone, however, is not limited to the perinatal period. We show that hormonal effects constitute lifelong influences on aspects of brain architecture and function. These influences represent a little-known and discussed--but extremely relevant--dimension of our understanding of the biological bases of behavior.