Hormone effects on brain structure
neuronal survival, connectivity, number or distribution of hormone receptors, neurochemistry
Sex differences in MPOA
Males have more synapses on dendritic shafts and fewer on dendtritic spines, castration on day 1 reverses this. Females normally have opposite pattern. Testosterone treatment given to females before day 4 results in a male like pattern.
Sex differences in SDN-POA
Males have larger (more cells) one than females. Thought to be do to the estrogenic metabolites of testosterone. Testosterone treatment of females and castration of males lead to male and female SDN-POA patterns respectively.
Testicular feminization mutation
rodent equivalent of androgen insensitivity syndrome. males have female external genitalia; normal SDN-POA size.
Lesions to POA
disrupt normal mating
Sex differences in Medial Amygdala
Male medial amygdala is large than female one.
Sex differences in BNST
Male BNST larger than female one
Sex differences in AVPV
regulates ovulation. volume of nucleus greater in females. males castrated before day 10 have female-like volumes.
Sex differences in INAH in humans
INAH2 and INAH3 bigger in males. INAH1 and INAH4 are similar.
reported as smaller in homosexual males.
Sex differences in SNB
Nucleus in spinal cord of male rates much larger than in females. Motor neurons control muscles attached to the base of the penis that are involved in erection.In females the bublocavernosus and levator ani muscles are atrophied or completely missing.
Estrogen in SNB
has no effect on muscle or neuron survival.
Testosterone in SNB
rescues both muscle and neuron survival
Androgens in SNB
Androgen treatment rescues muscles in females. If muscle is already die, the androgens can't save it. `
human version of the SNB. Bulbocavernosus muscles present in both males and females. Differences in motor neuron not as pronounced.
Lesions in HVC and RA
disrupt bird song in adult birds.
Recursive loop in song learning
HVC to area x to dlm to iman to ra. also known as "anterior forebrain pathway" damage to structure can cause song abnormalities.
Sensory Stage Song Learning
Young bird hears and memorizes adult songs
Sensory-motor Stage Song Learning
Young bird tries to reproduce song from memory. Trial and error learning.
HVC song learning
large and more androgen receptors in males
RA song learning
larger in males
IMAN song learning
neurons in males have more androgen receptors
activated by testosterone
Estorgens song learning
masculinity song circuitry
Androgens song learning
activate song circuitry
Urinary Posture dogs
postpubertal females treated with testosterone before and after birth showed male urinary posture 50% of the time. Males castrated shortly after birth still shift to male urinary posture at puberty. (Organized by testosterone)
Rough and tumble play rhesus monkeys
males engage in more frequent rough and tumble play than females. Pseuohermaphrodites show frequencies between normal males and females. Castration did not change play frequencies. (organized by androgens)
For most human behaviors
differences within sexes greater than between sexes
initial processing of sensory information as it enters the nervous system.
transduction of this sensory information into biologically meaningful information
at what level can a stimulus be detected
at what point can a difference between 2 stimuli be detected.
given a choice, what stimuli are preferred?
females have lower threshold and less tolerance compares to males. Females have greater sensitivity to cutaneous and visceral pain; lower sensitivity to muscular pain.
Woman score better than men on odor detection on identification. Woman are 1000x more sensitive to musk like odors.
Periovulatory and early pregnancy
Menstruating and late pregnancy
females show more sensitivity than males. Females show more discrimination between different tastes. Females show estrogen dependent preference for sweet tastes.
Preference for sweet tastes
organized by lack of androgen, activated by estrogen in adulthood.
women are more sensitive than men; can hear pure tones at lower threshold.
prefer auditory information as a reward
prefer visual information as a reward
females have louder OAEs than males. Prenatal androgens masculinize.
men see better than women. women can tolerate higher light intensity and adapt to darkness more quickly than men.
Male rats vision
Have 20% more neurons in primary visual cortex than females.
tendency for cognitive skills to be concentrated in one hemisphere or the other.
Right ear advantage
sound detection is usually better from the right ear, left hemisphere better at sound processing.
For right handers
right hemisphere used for spatial processing; left hemisphere used for verbal processing
are less lateralized than male brains. Turner syndrome females and those exposed to DES prenatally have male-like lateralization.
women are better a verbal skills including language comprehension, language acquisition, spelling, verbal fluency and grammar skills.
Differences in Verbal Skills
are not organized by hormones. Social and environmental factors cannot be ruled out.
larger on left although size is less lateralized in females involved in speech
Superior temporal cortex/Broca's area
volumes larger in females, also involved in speech.
males use left inferior frontal gyrus. Females use both right and left inferior frontal gyri
Woman score better on
preceptual skills, fine motor skills, mathematical calculations
Men score better on
Gross Motor skills, Quantitative task, visuospatial abilities.
after puberty males perform better than females on visuospatial tasks
Male Sexual Behavior
all behavior that are necessary and sufficient to bring male (sperm) and female (ova) gametes together
sex drive or libido= motivational force that drives an individual to seek sex
copulation or mating
seeking sex: all behaviors used by males to gain access to a female
having sex; involves potency, the capability of having sex and performance, actual mating
assuming mating position but no penis insertion
insertion of penis into vagina during amount
forceful expulsion of semen, often accompanied by a sperm plug that blocks intromission by other males.
time to first mount
male is required to "work" or endure pain to gain access to female
inter mount interval
time between successive mounts
inter intromission interval
time between successive intromissions
time from 1st intromission to ejaculation
Post ejaculatory interval
time between ejaculation and next copulatory series
show decreased motivation and performance, grows more pronounced over time. testosterone can restore sexual behavior but not simultaneously.
androgens given immediately
androgens given after behavior has stopped
experience "natural" castration going into their non-breeding season ex. syrian hamsters in the fall.
Testosterone and androstenedione
can restore sexual behavior in castrates
can restore sexual behavior. both testosterine and androstendione can be converted to it!
reduces male sexual behavior (Aromatase inhibitor). these effects can be overcome with estrogen treatment.
Castration of spinally transected rats
penile reflexes start to decline over 24 hours. gone by 12 days. normal reflexes can be maintained or restored by testosterone implants. DHT maintains or restores penile reflexes.
Testosterone important for
sexual motivation and sexual performance
Estrogen important for
maintaining or restoring sexual behavior via action on the central nervous system.
DHT critical for
maintaining or restoring sexual performance via action on the peripheral nervous system.
lesions of it eliminate sexual performance but no motivation. testosterone treatment does not restore behavior
MPOA critical for
processing sensory cues.
main olfactory bulb
accessory olfactory bulb
critical for male reproductive behavior.
receives information from main olfactory bulb
receives information from accessory olfactory bulb and "olfactory aygdala"; sends information to various hypothalamic nuclei.
removal reduces sexual motivation but not performance
removal reduces sexual performance.
peak in teens and early 20s for human males
the period during which a female is sexually receptive , "in heat"
the 4-5 day female reproductive cycle in rodents
Vaginal cytological assay
shows changes in vaginal cell types. A modified version is the pap test
mature follicle containing egg to be released. Source of estrogens
develops from a follicle following release of egg. Source of progesterone
Castration of females
leads to increasing levels of gonadotropin and gonadotropin-releasing hormone
after ovulation. corpus luteum develops from ruptured follicle. cornified epithelial cells.
new follicles develop. leukocytes and few nucleated epithelial cells appear. Cornified epithelial cells decrease.
follicles continue to mature
maximal follicular development. behavioral estrus occurs. Increased number of nucleated epithelial cells.
stimulate release of LH and FSH
LH and FSH
cause steady increase in estrogen
GnRH release by hypothalamus. Development of several follicles by FSH.
Ruptured follicle becomes corpus luteum. Corpus luteum secretes progesterone.
stimulates release of GnRH
Kiss1 expression in ARC leading to reduced GnRH and LH/FSH release
Kiss1 expression in AVPV leading to increased GnRH and LH/FSH release (females only)
stimulus value for a male
extent to which female initiate copulation. equivalent to "appetitive" phase in male sexual behavior. For most mammals, must have high estrogen.
responsiveness to male's sexual advances. equivalent to "consummatory" phase in males. hMust have high estrogen. Requires functional estrogen receptors.
Ovariectomized and anestrous females
are not attractive
use a three chamber preference test.
behaviors that establish and maintain proximity to males.
release of egg from follicle
cyclical release of eggs based on a set time cycle
release of eggs contingent upon external stimuli
luteal phase when the uterus prepares for pregnancy
formation of corpora lutea always follows ovulation
formation of corpora lutea requires additional stimuli.
Any behavior that contributes directly to the survival of fertilized eggs or offspring that have left the females body.
When 2 adults are required for survival of young
a parental male will have greater reproductive success than a nonparental male.
extent to which parents compromise their ability to produce additional offspring in order to assist their current offspring.
well developed, ready to cope with environment early on; surivival does not depend much or at all on parental intervention
immature, helpless; limited movement, cannot thermoregulate
can see and thermoregulate but cannot move indepedently
young are highly altricial, embryo-like. females have pouches that contain mammary glands and are used to carry young.
young are "born" at an even earlier developmental stage : eggs
Eutherian Patterin 1
mother provides food, care and shelter
Eutherian Pattern 2
precocial young, exclusive bond forms between mother and offspring
Eutherian Pattern 3
semiprecocial young, helpless but able to clin to mother
Critical components of rat maternal behavior
licking and grooming of pups, nursing, pup retrieval.
foster pups are presented to adults to see if and how long it will take to induce parental behavior. invovles different latencies depending on physiological state of primiparous feamales.
oxytocin levels increase
during parturition. injection into brain ovariectomized, estrogen-treated female rats causes expression of maternal behavior in 1 hour.
Anesthetizing mother's muzzle and/or nipples
reduces maternal behavior due to lack of sensory information needed.
MPOA and maternal behavior
involved in maternal motivation and performance.
Lesions to the chemosensory system
reduces latency to maternal behavior
Olfactory and vomeronasal inputs
to the MPOA normally inhibit maternal behavior.