The reader will discover that the exact mechanism in which testosterone masculinizes the fetal and neonatal brain is not fully understood, however the common theme in the following lectures and essays is that prenatal hormones are very important to the sexual differentiation process of the brain.

 

---

Harvard Medical School : Five Themes at The Interface of  Brain and Education, He, She, I: When and How do you know what you are? Speaker: Dr. Daniel Federman, Senior Dean for Alumni Relations and Clinical Teaching, Harvard Medical School 204)

"How and when does the infant internalize the information of which sex he or she belongs to? The classic view was that the development of gender identity reflected social cues from parents and others in the environment who knew what sex the patient's genitalia reflected. This formulation has been revised in the past 25 years to recognize a greater role for hormones in organizing the central nervous system. It is thus likely that a combination of biological and experiential learning determines gender identity."

 

---

M Hines Professor of Psychology Society for Endocrinology , Psychological Development in Intersex Conditions, Endocrine Nurses Training Course 4-6 September 2000 .

" Thus, it is possible that hormone levels during early development influence human neural and behavioural sexual differentiation in a manner similar to that documented experimentally in rodents and non-human primates. If so, intersex conditions, particularly those that involve gonadal hormone abnormalities that produce alterations in the external genitalia might also be expected to produce alterations in brain development and sex-typical behaviour. "

 DR. Hines has a new book out entitled Brain Gender 209)

---

University at Albany , Wagner , Sexual Differentiation of Brain and Behavior, How do sex differences in behavior develop? Nature vs. Nurture 142)

"From rodent studies

•  Male and female brains become different because of differential exposure to steroid hormones during development

• Sex differences in brain presumably underlie sex differences in behavior "
  

---

University of Colorado at Boulder , Brain and Behavior 

REPRODUCTION & SEXUAL BEHAVIOR  143)

"3. Sexual differentiation of the nervous system occurs between males and females, such as Spinal Nucleus Bulbocavernosus (SNB) in the male spinal cord or the enlarged Sexual Dimorphic Nucleus (SDN) in the male hypothalamus. The Medial Preoptic area (MPA), Amygdala (AMG), and Basal Nucleus of the Striatum Terminalis (bNST) are critical for male sexual behavior. These brain areas are T-sensitive. Female sexual behavior (e.g., lordosis behavior) is regulated in part by the Ventromedial hypothalamus (VMH) and the AMG. "

 

---

University of Massachusetts Amherst  Geert J. De Vries  Hormonal Control of Sexual Differentiation 144)

"Gonadal hormones profoundly influence brain physiology and behavior in vertebrates. During development, these hormones determine whether brains will function in a typical male or female fashion."

 

---

Medical Neuroscience Course, Dr. Piasecki - Sexuality - PowerPoint (1.2 Mb), Neuroscience of Sexuality 145)

 "Brain Masculinization

• Default is female

• Timing of testosterone surge important for adequate number and type of receptors "

"Brain Structure and Human sexuality

• Small differences in brain structure: Large differences in sexual behavior

• Brain Dimorphisms result from effects of circulating hormones during development"

"Conclusions: Gender is determined by

• Genes

• X,Y

• Synchronization of  hormonal surges, effects of enzymes and intact receptor systems

• Mismatches between brain and body development are possible"

---

Dr. Alexander Thiele University of Newcastle upon Tyne Lecture 7: Social emotions –‘the sexual brain’ Handout 147)

"Thus, a brain that is entirely male or female hardly exists, these terms represent the extreme poles that are rarely realized in nature. In reality all sorts of intermediaries are realized in male and female bodies. The possible permutations allow for cross sexual variants, with the result that male brains can reside in female bodies and vice versa. The discovery of cross-gender desires for the individual can be quite painful, especially in intolerant (and sometimes repressive) societies that have created a norm of sexual behaviour deemed acceptable."

Slides 146)

"The primordial plan for both female and male fetuses in mammals is initially feminine.

 Contrary to some creation myths, in mammals,maleness arises from femaleness, not the other  way round.

 Masculinisation results from organisational effects of fetal testosterone (and its derivatives),  which in humans occurs during the second trimester of pregnancy.

 To be masculinised means that certain areas of the brain grow larger, while others remain  smaller.

 These differences to some extend explain sexual behaviours and preferences even in humans "

 

---

University of Massachusetts Amherst. PSYCH 335 Motivation and Emotion: Biological motives: sex Revised (spring '03) last revision 5/3/03 161)

"V. Sexual differentiation of the brain.

A. Events before birth contribute to determining sex behavior as adults and in humans gender identity.

B. During prenatal period the secretion of T from the testes has a masculinizing affect on the male brain

C. Early in prenatal development the testes secrete T in XY individuals which causes masculinization of the brain.

1. In particular, the hypothalamus is affected but other brain regions are also changed

2. To accomplish this T from testes is aromatized to estrogen in the brain

3. The default form of the brain is feminine--no hormone action

4. Estradiol does not do this in females because ovaries are not developed and mom's E. is blocked by a binding protein, alpha fetoprotein, in fetal circulation.

D. The idea that the structure of brain can be changed strongly suggests that behavior will also be different between male and females."

Note: the above lecture discusses DES in relation to masculinizing female behavior.

 

---

University Of South Florida , EXPERIMENTAL PSYCHOLOGY PSY 3403 Instructor: Scott Husband, MA 162)

"D. The hormonal basis of sex

1. Adrenogenital syndrome: Genetic female with male genitals

2. Androgen insensitivity: Male embryo unresponsive to male hormones

3. Sexual behavior

a. Sexual orientation: Heterosexual, bisexual, gay

b. Transsexualism: Gender doesn't match biological sex "

---

The English Language Psychology Program at the Faculty of Humanities of the Eötvös Loránd University The Institute of Psychology 163)

"PY–F04 Gender Differences, the Development of Gender Roles (1 lecture/practice, exam/practice mark)  The development of gender identity. Inherited biological bases, the effect of androgen hormones on the development of brain in the fetal period and infancy. The influence of cognitive development and socialization on the development of gender identity. The development of gender roles; cross-cultural comparisons. The development of social relationships between the sexes. "

 

---

The University Of Hawaii: A Sexologist in the Outback - Queensland, Australia (Professor Milton Diamond PhD and Dr Constance Brinton-Diamond PhD) 205)

"Are differences in sexual orientation and gender identity determined by genetics and hormonal influences--or are they a lifestyle choice? "

 

---

The University Of Southern Maine: Psychopathology ~ PSY333 Presented by William Gayton, Ph.D. Ch 13 SEXUAL DISORDERS Gender Identity Disorder 207)

"Gender Identity Disorder

Strong and persistent cross-gender indentification
(desire to be the other gender)
Persistent discomfort with one's anatomical sex
Significant distress or impairment is present

Etiology

Biogenic
Hormonal imbalance during prenatal development
(exposure to higher than average levels of hormones related to the opposite sex)

Psychoanalytic
Inability to resolve oedipal conflict

Behavioral
Inappropriate learning
(i.e. parental encouragement of feminine behavior) "

---

Arizon State University :  Dr. F. Scott Christopher ,  FAS 332:  Human Sexuality  : Gender identity  216)

"Gender Identity

Gender Identity as a Normal, Developmental, Biological Process

Chromosomes
Development of Internal Reproductive Structures

Gonads
At 6 weeks
At 8 weeks

Males & Wolffian ducts
Females & Müellerian ducts
Adams principle

Development of External Genitals

At 6 weeks

Males & Dihydrotestosterone (DHT)
Females & absence of male hormones
homologous sex organs

Sex Differentiation of the Brain

Prenatal hormones
Animal research
Humans & prenatal hormones"

---

 

Harbor College Biology of Sex and Gender, Donette Steele, M.A./ Clinical Psychology  249)

"Prenatal Hormones and the Brain

The presence of testosterone during fetal development masculinizes certain parts of the brain.

 Absence of testosterone results in feminization"

---

 

The University of Plymouth, Department of Psychology PSY 364 , The nature and nurture of Gender. 250)

"Effect of testosterone on the brain

We have seen that early exposure to testosterone affects the external genitalia and adult behaviour, but does it also change the brain? This is an important question. There is evidence that the brains of male and female rodents are structurally different, and that this sexual dimorphism is caused by exposure to androgen during a critical period of development.

An area of the hypothalamus at the base of the brain called the sexually dimorphic nucleus of the preoptic area (SDN-POA) is much larger in male rats than in females. These diagrams show the location of this sexual dimorphism. You can load an animation that explains the relationship between the saggital and coronal views of the brain in a separate browser window."

---

Exploring the Biological Contributions to Human Health: Does Sex Matter? (2001) Institute of Medicine (IOM) 164)  Page 80 Psychosexual Differentiation .  Discusses the role of testosterone in the sexual differentiation of the brain

---

Sheldon Krimsky: Chemicals Health and the Environment , Peace and Justice studies at Tufts University , a very comprehensive syllabus 197)

Some conferences which discuss the role of hormones and the brain
e.hormone Events page	Lists events taking place around the world discussing EDC's, an excellent place to start
2nd International Meeting STEROIDS AND NERVOUS SYSTEM	February 22-26, 2003 Villa Gualino,TORINO, Italy
US/Japan INTERNATIONAL SYMPOSIUM ON NEUROPLASTICITY DEVELOPMENT AND STEROID HORMONE ACTION	September 26-29, 2000 Hawaii-Imin International Conference Center Honolulu, HI

 

---

 Previous   Next

[Introduction] [Definitions] [Discussion] [Lectures] [Gender Identity] [Intersex] [Table1] [Table2] [Table3] [Research] [Genetics] [Questions] [Conclusions] [Links] [Timelines] [Responsibility]