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SEXUAL DIMORPHISMS IN HUMAN BRAIN (Swaab et al., Hormones and Behavior, 2001. Problems to study humans. Use of bioptic material No possibility of having homogenous groups Difficulties to find the clinical history Presence of brain pathologies
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SEXUAL DIMORPHISMSINHUMAN BRAIN(Swaab et al., Hormones and Behavior, 2001
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)
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%) General features
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 Comparison
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)
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 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 (Le Vay, Science 1991)
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 Comparison
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 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 (Le Vay, Science 1991)
Dimorphism in relation to gender and sexual orientation VOLUME Suprachiasmatic nucleus SDN-POA Swaab et al, Progr Brain Res, 1992
Dimorphism in relation to gender and sexual orientations Suprachiasmatic nucleus SDN-POA
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. men women Homosexual men transsexual men
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 men transsexual men
Man Oxytocin neurons in the human SON Woman Oxytocin neurons do not shown any difference