PM Kruijver, Dick Swaab) also examined subjects with hormone-related disorders and found no pattern between those disorders and the BSTc while the single untreated male-to-female transsexual had a female-typical number of cells. They concluded that the BSTc provides evidence for a neurobiological basis of gender identity and proposed that such was determined before birth. Hormone replacement therapy has been shown to influence hypothalamic size, even though the study tried to do this by including non-transsexual male and female controls which, for a variety of medical reasons, had experienced hormone reversal. The statement about the neurobiological basis from birth has later been brought to question, though not refuted, by a follow up study by the same group which found that the sexual dimorphism of the BSTc is not present before adulthood (approximately 22 years of age) even though transsexuals report being aware of their gender identity since childhood. Since somatostatin-expressing neurons typically block dendritic inputs to the postsynaptic neuron, thus inhibiting signals traveling through associated structures, it is believed that the larger bed nucleus of the stria terminalis found in men (including transgender men) reduce the startle response in men and may be responsible for the higher incidence of specific phobias in women, and a possible source for the stereotype of women being afraid of mice. Oxytocin receptor activity in the BNST is important for social recognition in rats. Both male and female rats that received a microinjection of oxytocin receptor antagonist had lower social recognition scores than rats that received a vehicle injection, and microinjections of oxytocin into the BNST enhanced social memory in male, but not female, rats. Reduction of the size of the bed nucleus of the stria terminalis has been observed in pedophilic male perpetrators, in addition to reductions in the right amygdala, hypothalamus and abnormalities in related structures. The authors propose that childhood deficits in the BNST and medial amygdala may cause inhibition of sexual maturity. References External links Photo at University of Pennsylvania Overview at Everything2 Cerebrum