Psych
311 - Psychophysical Development
OUTLINES
Chapter 3
Origin and Function of Embryonic Behavior
Rev.
Return to Syllabus
I. Hormones
A. Blood borne substances secreted by tissues cause the development and maintained of structure and behavior
1. Forbes 1949, Bethhold 1849 showed proof of endocrine function
a. Castrated young male foul and put testes in body cavity
b. Nerve supply did not reconnect to testes
c. Determined
that sexual functions are a result of the productive function of the testes’
action on the bloodstream
B. Reproductive System
1. Hormones are involved in sexual differentiations
2. Lillie 1916-17
studied the freemartin-female member of dizygotic
bovine twins.
a. Female
shows abnormalities-sterility, atrophic gonads that resemble ovaries and
testes, abnormal development of genital tract-in cases where there is a fusion
of some of the placental blood vessels.
b. Male was normal although male blood was thought to cause effects seen in female.
3. Attempts to produce freemartinism syndrome is cows failed although we know freemartinism is caused by germ cell of the male to the female or by the presents of a honadnrogenic substance that causes testicular development
4. Regardless
of sex each embryo contains the anglgen (basic
material) for both male and female genital ducts.
a. Wolffian ducts-male sex organs
b. Mullerian ducts-precursor of uterus, oviduct, and vagina
c. Male
ducts system develops when functional fetal testes are present and a female
system.
d. Female-clitoris arises from the genital tube
e. Male-tubercle develops into penis.
f. Direction
of development depends solely on whether testicular secretions are present.
5. Testicular feminizing syndrome - The absence of androgen sensitive tissue is inherited as an x-linked recessive trait.
a. Males born with this are often identified as female at birth as they developed with out testes
b. Usually not discovered until puberty
c. Usually given hormone to maintain female sexual traits.
6. Pfeiffer study demonstrated the principle of preferential
female differentiation applies to reproduction function
a. Gonadotropins act on the ovary to induce ovulation
b. Rats of both sexes were gonadectomized
1) some were given testicular transplants
2) provides them with androgen
3) at adult each had ovarian transplant
4) assessed for ovulation
5) no ovulation
6) found that ovulation does not occur if testicular secreations are present in early life
7) in the absence of androgen both male and females exhibit ovulation
c. Site of action of androgen is the pituitary
1) male pituitary-one secreting gonadtropins tonically results from early androgenic stumulation
2) female pituitary that secretes gonadotropins cyclically develops in the absence of androgen
3) later research proved this to be wrong
7. Other Research
a. Other research demonstrated that the site of action of androgen involves the brain
1) arcuate nuclei synthesizes and releases a hormone that acts on the pituitary
2) preoptic nuclei causes the arcuate nucleus to change its firing pattern from tonic to cyclic
b. Early
androgen stimulation promotes the later display of male-like reproductive
behaviors
C. Reproductive Behavior
1.
a. Injected pregnant guinea pigs daily with synthetic androgen testosterone propionate throughout most of the gestation period
b. Between 90 and 160 days they were gonadectomized and tested
c. Found that prenatal exposure to testosterone permanently suppresses the females capacity to respond to estrogen and progesterone by becoming sexually receptive
1) Also found that the guinea pigs exhibited elevated levels of male copulatory activities in response to testosterone propionate stimulation given in adult life
2. Grady,
a. Castrated male rats on either day 1, 5, 20, 30, 50 of life
1) Then given estrogen and progesterone and tested for the display of sexual behavior
b. Found that males castrated on day 1 or 5 displayed much more female sex behavior in response to estrogen plus progesterone treatment then did males castrated after day 5
3. Gerall, Dunlap and Hendricks (1972)
a. Castrated new born make rats and gave them ovarian transplants
1) Ovaries removed on day 60
2) Tested for female sexual behavior on either day 90 or 160
b. Found that males given ovaries displayed more female behaviors than those not given the transplant
4. Dohler et al, 1984
a. Hypothesized that high levels of estrogen cause sexual differentiation to proceed in a male typical direction, whereas moderate levels of estrogen lead to female differentiation
II. Hormones and nonreproductive Behavior
A. Aggression
1. Testicular secretion are involved in the display of aggressive behavior.
2. Males, typically more aggressive then females, can be made tractable by castration
3.
a. Reported that aggression is reduced in males following castration and can be reinstated by testosterone replacement therapy in both chimps and rats.
4. Edwards
a. Suggests that aggression, like sexual behavior, follows the principle of preferential female differentiation: In the absence of androgen exposure and regardless of genetic sex, a relatively non-aggressive organism develops.
b. He injected testosterone propionate into some newborn female mice and gave other oil vehicle
c. When adults, the mice were ovariectomized and administered daily injections of testosterone in dosages that started out low and increased weekly.
d. When the females were placed with the males it was noted that neonatal androgen exposure promotes later responsiveness to androgen; females only attack males if testosterone was given soon after birth.
e. It was later proven that fighting
can be activated in animals that have not been exposed to androgen during
prenatal development.
5. Savare, Davis, and Gandelman
a. Such aggression procedes at a much slower pace.
b. Nonperinatally androgenized animals require upward of a month of daily injections.
c. They concluded that androgen stimultion during early development does not institute behavioral responsivness to testosterone, rather it is enhanced.
d. Additional parallels exist between the hormonal involvement in reproduction and aggression.
1) Perinatally androgenized animals require a much shorter exposure to androgen then do nonandrogenized animals.
e. Early postnatal androgen exposure is more effective then embryonic exposure.
6. Simon and Whalen
a. Proposed that masculinization of neutral sustance mediating aggression may involved androgen and estrogen.
b. Male copulatory activity is enhanced is some cases by perinatal androgen exposure.
B. Activity - Sex differences in activity levels
1. Blizzard, Lippman and Chen
a. Open field activity related to exploration and investigation
b. Differences can be modulated by hormonal manipulation
1) Testosterone to females- between postnatal day 1 and 10 reduces display of activity to that of a male
2. Beatty, Scouten, Grotelueschen
a. Elimination
early androgenic stimulation can make males’ open field activity = females
3. Gentry and Wade
a. Running wheel activity- used to adjust energy expenditure to food intake
b. Females exhibit higher levels
4. Dawson, Cheng and Lou
a. Neonatal injections of gonadal hormones
1) Testosterone decreases female activity
2) Estrogen increases running in both sexes (but to lesser extent in males)
5. Assessment of Activity
a. Method
1) Place series of photocell beams across cage floor
2) As subject moves, beams are broken
3) Number of interruptions- measure of activity
b. Broida and Svare
1) Females more active
2) Gonadectomy
a) Reduces activity without eliminating sex differences
3) Males gonadectomized on day of birth more active than those on days 5, 10, 25
4) Neonatal androgen stimulation
a) Permanent attenuation of activity
b) Period of maximum sensitivity is within 1 week
c. Beatty and Beatty
1) First to report sex differences inquisition of avoidance response
a) Females superior to males
2) Testosterone injections reduced female’s avoidance
d. Denti and Negroni
1) Neonatal androgen exposure produces decrement in female avoidance behavior
2) Male performance increased by elimination early stimulation
6. Sex differences in Lashley III Maze
a. Males superior in learning the maze
1) Make fewer errors and retracings
2) Exposure of neonatal females to testosterone increases performance
b. Implications
1) Less active retards avoidance behavior
2) Less active advantageous in complex learning situations requiring deliberate responses
C. Taste Preference
1. Krecek
a. Sex differences modified by early hormone exposure
2. Valenstein, Kakoluwski and Cox // Wake and Zucker
a. By 60th life day- female consume more saline solution than males
b. This can be prevented by:
1) inject 2-day-old female with testosterone
2) By day 12- no effect
c. Also seen for sweet tastes
1) Administer testosterone to 5-day-old female, decrease predisposition for sweet flavors
3. Shapiro and Goldman
a. Increase preference for sweet shown by testicular feminized rats
b. Androgen suppresses preference exhibited by females for salt and sweet
D. Brain Asymmetry and Associated Behavior
1. Two brains hemispheres are not same
a. left hemisphere- body movements, language production comprehension
b. right hemisphere- emotion, music, art, abstract thought
c. differences are know as brain asymmetry
2. Brain asymmetry not only in humans
a. Canary, rat, chick
3. brain asymmetry related to presence of testosterone
a. Testosterone either slows growth of left side or promotes growth of right
4. Studies with non humans provide support for hypothesis that testosterone promotes brain asymmetry
E. Human Personality
1. The endocrine system in human behavioral development
a. Problems
1) dependent measure of behavior is personality. Personality tests don't assess behavior
2) direct manipulation of endocrine system cant be performed on humans
b. Approaches to studying endocrine system
1) study endocrine system disorders because genetic not hormonal
2) examine those exposed to administered hormones
3) correlation of particular behaviors of children with levels of hormones formed in blood
c. Endocrine
disorder CAH results from exposure of embryonic females to elevated levels of
androgen
1) Ehrhardt et al studies CAH girls
a) findings suggest CAH girls were masculanized, showing more interest in physical activity, careers and less interest in children and marriage, describing themselves as tomboys
2) a follow up study on 13 of the now adolescent females was performed
a) revealed an increase in dressing attractively but still low interest in becoming a parent
b) 11 of 30 women with a istory of CAH rated themselves as bisexual or homosexual
2. Ehrhardt and Money (1967)
a. Examined the children of women treated with synthetic hormones (progesterone)
b. Some of these had masculinizing properties
c. Results virtually identical to CAH sample
3. Reinisch (1981)
a. Reported males and females prenataly exposed to synthetic progestine score higher then same sex sibling controls on test to assess aggressive behavior
4. Reinisch and Karow (1977)
a. Studies children of estrogen and progestin treated mothers
b. High progestin exposed children were more independent and self-sufficient
c. High estrogen exposed children were more group oriented and group dependent
d. Reinisch and Karow characterized high progestin as inner directed and high estrogen as outer directed
5. Relation between hormones and mood derives not from specific effects of a given hormone but from a component the hormones have in common
a. Higher levels of hormones in general are associated with happy/excited moods
b. Lower levels of hormones are related to quiet/calm moods
III. Neuroanatomical Brain Dimorphism - The endocrine system influences behavioral development implies that hormones modify the central nervous system
A. Differences between neuroanatomical features of the female and male brain is governed by the endocrine system the same way it regulates the development of sexually dimorphic behavior
B. Most neurons from regions other then the amygdola make contact with preoptic neurons of the male brain by synapsing on a particular portion of the dendrite, the shaft
C. In contrast preoptic neurons of the female brain contain a larger portion of synapses on dendratic spines
D. Like behavioral development, physical development of the central nervous system is in part controlled by the endocrine system
1. Androgen leads to the elaboration of male typical patterns of behavior
2. The absence of sufficient androgenic stimulation, both behavioral and nervous system morphology take a female course
IV. Within-Sex Variability
A. Most males exhibit higher levels of spontaneous fighting behavior than females.
B. Many factors account for individual variation: Temperature, Uterine position and maternal stress.
C. Temperature
1. Roffi
a. Marked
effect of ambient temperature on testosterone levels of newborn.
b. It is apparent that testosterone levels are low in pups exposed to temperatures of 18 and 21 degrees C.
c. Another experiment was performed to determine if the lowered testosterone levels seen after cooling can be increased by exposure to a normal temperature.
1) After
two hours in 18 degrees C, newborn male pups were placed with lactating female.
2) Cooling for the first two hours of life delays the testosterone search by two hours; peak occurs at four hours.
D. Uterine Position
1. Sexual Differentiation of the young is in part determined by their position within the uterus relative to other embryos.
2. Clemens (1974)
a. Adult
female rats had been situated in uterus between two male embryos (mFm) exhibited higher levels of male sex behavior in
response to androgen treatment than females that had no been located contiguous
to males.
b. Androgen
from amniotic males is conveyed in some manner to the female.
1) Males show enhanced amounts of sexual behavior and lower levels of aggression.
3. Gonadal secretions are transmitted non-passively through amniotic diffusion, but actively through the maternal circulatory system.
4. Fetal human testes begin to produce testosterone between days 70 and 90 of gestation cause testosterone levels to rise in amniotic fluid surrounding the male.
E. Prenatal Stress
1. Relation of maternal stess (prenatal stress) to the later expression of sexually dimorphic behavior.
a. First considered by Ward (1972)
then
b. Results: Rat studies found that males born to stressed females displayed an increase in female sex behavior and a decrease in male sex behavior. Male stressed rats were demasculinized and feminized.
2. Prenatal stress in rats leads to a reduction of the following in males
a. killing of young
b. inter-male fighting
c. asymmetry and thickness of cerebral cortex
d. latencies to exhibit maternal like behavior
e. demasculinizes anitomically dimorphic regions of the preoptic area of the brain
3. Link between prenatal stressful events and sexuality
a. Dorner performed a series of studies, which concluded that
prenatal stress may be regarded as a risk factor for inborn bi and homo
sexuality in men.
IV. Concluding Comments