1. SEXUAL DIMORPHISMS IN HUMAN BRAIN (Swaab et al., Hormones and Behavior, 2001

2. Problems to study humans Use of bioptic material No possibility of having homogenous groups Difficulties to find the clinical history Presence of brain pathologies The legal period for autopsy is depending by the local laws (in Italy 48 hours postmortem, in Netherlands 8 hours)

3. General features Woman Weight: 1171 gr 19 mil of neurons Higher cerebral metabolism Higher linguistic capacities Man Weight: 1308 gr 23 mil of neurons Higher cerebral volume in childrens Higher serotonin synthesis (+53%)

4. Sexual dimorphism according to Swaab

5. Sexual dimorphism according to Gorsky

8. Comparison SDN-POA volume 2.2 higher in man than in woman Cell number about 2 times higher in man INAH INAH1 8% > in HIV+ INAH2 volume 2 times higher in man INAH3 volume 3 times in man INAH4 no dimorphism

9. Development and sexual differentiation of the SDN-POA Cell number reach a peak value around 2-4 years postnatally, after which a sexual differentiation occurs due to a reduction in cell number in females, whereas cell number in males remains approximately unchanged up to age of 50 years (Hofman and Swaab, Exp Clin Endocrinol, 1991)

10. Dimorphism of INAH in relation to gender and sexual orientation Individuals who died of complications of AIDS Individuals who died of causes other than AIDS An individual who was a bisexual man and died of AIDS (Le Vay, Science 1991) INAH 3 > in heterosexual men Homosexual men INAH 3 = Women INAH 3 INAH 3 is dimorphic with sexual orientation The sexual orientation has a biological substrate

11. Comparison SDN-POA volume 2.2 higher in man than in woman Cell number about 2 times higher in man INAH INAH1 8% > in HIV+ INAH2 volume 2 times higher in man INAH3 volume 3 times in man INAH4 no dimorphism

12. Dimorphism of INAH in relation to gender and sexual orientation Individuals who died of complications of AIDS Individuals who died of causes other than AIDS An individual who was a bisexual man and died of AIDS (Le Vay, Science 1991) INAH 3 > in heterosexual men Homosexual men INAH 3 = Women INAH 3 INAH 3 is dimorphic with sexual orientation The sexual orientation has a biological substrate

14. Dimorphism in relation to gender and sexual orientation SDN-POA Suprachiasmatic nucleus Swaab et al, Progr Brain Res, 1992 VOLUME

15. Dimorphism in relation to gender and sexual orientations Suprachiasmatic nucleus SDN-POA

16. The nucleus of the Stria Terminalis The nucleus of the stria terminalis (BST) may be easily identifyed by means of Somatostatin distribution. Larger volume in men (a) than in women (b) In homosexual men (c) the volume is similar to that of normal men In transsexual men with female orientation (d) the nucleus has a volume similar to that of women The BST volume is reflecting the sexual orientation rather than the genetic sex. menwomen Homosexual mentranssexual men

17. The nucleus of the Stria Terminalis The nucleus of the stria terminalis (BST) may be easily identifyed by means of VIP distribution. Larger volume in men (a) than in women (b) In homosexual men (c) the volume is similar to that of normal men In transsexual men with female orientation (d) the nucleus has a volume similar to that of women The BST volume is reflecting the sexual orientation rather than the genetic sex. men women Homosexual mentranssexual men

18. Man Woman Oxytocin neurons in the human SON Oxytocin neurons do not shown any difference