2. The Endocrine System
• The body’s slow chemical communication
system; a set of glands that secrete hormones
into the blood stream.
• Maintenance of the internal environment in the
body (maintaining the optimum biochemical
environment)
• Integration and regulation of growth and
development
• Control, maintenance and instigation of sexual
reproduction, including gametogenesis, coitus,
fertilization, fetal growth and development and
nourishment of the newborn
•1. Sex steroids are sex-specific: In fact
both males and females produce
androgens and estrogens though their
relative concentrations differ.
•2. Individual differences in behaviour
and physiology reflect differences in
hormone concentration: While overall
concentration is indeed important, of
equal importance is the receptivity of the
cells to the hormone.A high hormone
concentration will have little effect if
cells lack receptivity, an excellent
example of this is Androgen Insensitivity
Syndrome.
Misunderstandings
The study of the relationship between hormones and behavior
Hormones affect behavior and behavior feeds back to affect hormones
Hormones↔Behavior
3. Sexual Behavior
Cognitive Behavior
Aggression and Mood
Trust and Social Standing
Sleep
The relationship between testosterone levels and
sexual dysfunction, and how sleep may affect
both.Changes in testosterone levels occur
naturally during sleep, both in men and women.
Testosterone levels rise during sleep and
decrease during waking hours. Research has
shown that the highest levels of testosterone
happen during REM sleep, the deep, restorative
sleep that occurs mostly late in the nightly sleep
cycle. Sleep disorders, including interrupted
sleep and lack of sleep reduces the amount of
REM sleep, will frequently lead to low
testosterone levels. And this is important for men
and women.
Evidence of a connection between sex hormones and
cognitive functioning came first from studies of men and
women with endocrine dysfunction: phenotypic women
with Turner’s syndrome, kwashiorkor-induced endocrine
dysfunction in boys, men with hypogonadotrophic
hypogonadism and children with congenital adrenal
hyperplasia. Direct manipulation of steroid hormone levels
supports the conclusion that androgens play a role in
cognition.
Positive effects of testosterone treatment were also
observed when normal, ageing men were given
testosterone to enhance sexual function; as a side-effect
they showed improved performance on visual–spatial
tests (reviewed in Christiansen 1999).
4. First endocrinology experiment Hormone/Behaviour
Relationships
Sex differences in appearance are often more pronounced in nonhuman
animals than in humans. Male birds particularly, for example roosters,
tend to have physical features that differ from the females and also differ
significantly in size
•If we remove the source of a particular hormone then a
behaviour that is assumed to depend upon that hormone
should disappear. E.g removal of testosterone by castration
dramatically reduces sexual desire and aggression in many
male animals.
. Once a behaviour has ceased following hormone removal,
we can restore hormone function and see if the behaviour
returns. E.g administration of testosterone to castrated adult
males restores aggressive behaviours and the mating urge.
. If hormones and certain behaviours are related, then we
should expect that alterations in the relative concentration of
a hormone should produce related alterations in a behaviour.
E.g aggression should be higher when circulating levels of
testosterone are higher.
5. Normal Rooster Normal Rooster Capon
Naturalistic observations of
changes in behavior and
appearance of roosters with
age and season.
-Castrated 6 roosters.
-Re-implanted a testis in 2
roosters.
-Transplanted a testis from
another bird in 2 roosters.
-Left 2 castrated roosters to
develop into capons.
Berthold’s Experiment
6. Idiopathic Hypogonadotropic Hypogonadism(IHH)
• This is caused by the insufficient release of
gonadotropin releasing hormone from the
hypothalamus.
• It is sometimes referred to as ‘Kallman’s
Syndrome’.
• Affected males are genetically normal, but
do not receive sufficient testosterone before
birth.
• Their genitals remain relatively unaffected
due to the influence of maternal androgens,
but at puberty secondary male sex
characteristics fail to appear.
•In Kallmann syndrome, the sense of smell is either
diminished (hyposmia) or completely absent (anosmia). This
feature distinguishes Kallmann syndrome from most other
forms of hypogonadotropic hypogonadism, which do not
affect the sense of smell. Many people with Kallmann
syndrome are not aware that they are unable to detect odors
until the impairment is discovered through testing.
Kallmann syndrome can have a wide variety of additional
signs and symptoms. These include a failure of one kidney to
develop (unilateral renal agenesis), abnormalities of bones in
the fingers or toes, a cleft lip with or without an opening in the
roof of the mouth (a cleft palate), abnormal eye movements,
hearing loss, and abnormalities of tooth development. Some
affected individuals have a feature called bimanual
synkinesis, in which the movements of one hand are mirrored
by the other hand. Bimanual synkinesis can make it difficult
to do tasks that require the hands to move separately, such
as playing a musical instrument.
7. Turner’s Syndrome.
• This syndrome was first described by Turner (1938).
• It only affects females in which all or part of one X chromosome
is deleted.
• This leads to a failure in ovary development, and produces short
stature and physical anomalies such as webbing of the neck.
• Externally, such individuals appear female but as they fail to
produce female sex hormones they remain sexually immature
unless provided with hormone replacements.
• They remain infertile.
• The most common feature of Turner syndrome is short stature,
which becomes evident by about age 5. An early loss of ovarian
function (ovarian hypofunction or premature ovarian failure) is
also very common. The ovaries develop normally at first, but egg
cells (oocytes) usually die prematurely and most ovarian tissue
degenerates before birth. Many affected girls do not undergo
puberty unless they receive hormone therapy, and most are
unable to conceive (infertile). A small percentage of females with
Turner syndrome retain normal ovarian function through young
adulthood.
8. A turner syndrome appearance
About 30 percent of females with Turner
syndrome have extra folds of skin on the neck
(webbed neck), a low hairline at the back of
the neck, puffiness or swelling (lymphedema)
of the hands and feet, skeletal abnormalities,
or kidney problems. One third to one half of
individuals with Turner syndrome are born with
a heart defect, such as a narrowing of the
large artery leaving the heart (coarctation of
the aorta) or abnormalities of the valve that
connects the aorta with the heart (the aortic
valve). Most girls and women with Turner
syndrome have normal intelligence.
Developmental delays, nonverbal learning
disabilities, and behavioral problems are
possible, although these characteristics vary
among affected individuals
9. 5- Reductase Deficiency
• This is a deficiency of the enzyme 5-reductase which
normally converts testosterone into
dihydrotestosterone.
• As dihydrotestosterone is principally responsible for
masculinising the external genitals before birth, males
with this syndrome are born with ambiguous genitalia
and undescended testes.
• They are often mistaken for females at birth and
reared as such.
• However at puberty when exposed to large amounts
of testosterone their body and external genitals
become more masculine.
5-alpha reductase deficiency is a condition that affects
male sexual development before birth and during puberty.
People with this condition are genetically male, with one X
and one Y chromosome in each cell, and they have male
gonads (testes). Their bodies, however, do not produce
enough of a hormone called dihydrotestosterone (DHT).
DHT has a critical role in male sexual development, and a
shortage of this hormone disrupts the formation of the
external sex organs before birth.
During puberty, an increase in the levels of male sex
hormones leads to the development of some secondary
sex characteristics, such as increased muscle mass,
deepening of the voice, development of pubic hair, and a
growth spurt. The penis and scrotum (the sac of skin that
holds the testes) grow larger. Unlike many men, people
with 5-alpha reductase deficiency do not develop much
facial or body hair. Most affected individuals are unable to
have biological children without assisted reproduction
Feminised Masculinised
10. In most mammals, males are more aggressive, and
castration reduces aggressive behavior.
Inter-male and territorial aggression increase after
puberty.
After a fight, the winner has higher, the looser lower
levels of testosterone.
Criminals: Age at first violent offense correlates with
testosterone levels.
Violent women prisoners have higher testosterone levels
than non-violent ones.
TESTOSTERONE and AGGRESSION
testosterone is involved in several aspects of social behavior, including
,social aggression ,infant/mate defense
sexual intimacy. dicrease in man , Increase in woman
The changes of testosterone concentrations, which varied in opposite
directions in the two sexes, may reflect changes in behavioural and/or
temperamental traits . To eliminate some of the biological differences
between the sexes, or to soften some male features in men and, in parallel,
to increase them in women
11. levels of the hormone largely responsible for fighting,
competing, and mating decrease when men settle down
and start a family. Other studies have shown that
testosterone begins to decline shortly after marriage, but
surges upward when unions end in divorce.
• Lower levels of testosterone may increase the likelihood
that men will stay home and care for their wives and
kids, while decreasing the likelihood they will go out
drinking with the guys and chase other women."
• "Single men invest only in mating, while fathers
decrease their mating efforts in favor of parenting."
• A man's testosterone levels drop significantly when he
holds an infant. Even holding a baby doll can decrease
levels of the male virility hormone.
• Married men, whether fathers or not, have markedly
lower testosterone levels than single males, according
to one of the first studies of how the hormone changes
when men marry and become father
600
650
700
750
Married Once Remarried
Never Married Married and divorced
Testosterone and Marriage
Testosterone and cortisol may then act within central
brain regions and peripheral tissues to facilitate adaptive
behavioral responses to a courting male, these
hormones could work centrally to prime courtship
modules that allow for more effective flirting, or
peripherally to mobilize energy reserves for shared
activity and possible sexual intercourse
testosterone receptors are distributed around
hypothalamic regions where testosterone eventually is
aromatized into estrogens, which then appear to
determine an actual increase in aggressiveness
12. • Women of reproductive ages in Western
industrial nations have higher levels of
ovarian hormones than those in rural
areas of undeveloped countries."
• "These differences mean that social and
ecological conditions exert a strong
influence on how high reproductive
hormones rise in young adults,“
• When ovulating, women prefer more
masculine faces.
• When not ovulating, they prefer only
slightly masculine faces.
• High estrogen women showed especially
strong shifts across the ovulatory cycle.
women release testosterone and cortisol to prime competitive
behavior and social dominance in situations where an
attractive man is paying greater attention to another woman
women who are in a relationship with a man in the same city
show lower levels of testosterone than women in a long-
distance relationship.This suggests that physical partner
presence has an effect on testosterone levels in women
estrogen-based contraceptives inhibit ovarian production of
testosterone and reduce levels of free testosterone via
increased hepatic synthesis of sex- hormone binding globulin
(SHBG)
It may be that single women experience
greater hormonal release to attractive male
candidates in courtship situations
regardless, this pattern of findings suggests
that there may be a relationship between
subjective romantic/sexual interest and a
measurable increase in testosterone
13.
14. Pheromones
• These are chemicals derived from sex hormones
which are manufactured and released by the apocrine
glands.
• They are released into the environment via sweat and
urine where they are detected by individuals of the
same species in whom they activate specific
physiological and behavioural responses.
Lee-Boot effect: When groups of female mice are housed together their estrus cycles slow
down and stop.
Whitten effect: If groups of female mice are then exposed to an adult male mouse (or to the
odour of his urine) they begin estrus again and their cycles become synchronised.
Similar menstrual synchrony has been reported in human females sharing accommodation.
Vandenburg effect: The presence of an unrelated adult male causes the acceleration of
puberty in female rats. This has also been reported for human females in the presence of a
stepfather.
Bruce effect: When a pregnant female mouse is housed with a male mouse who is not the
father the pregnancy is likely to fail and she quickly comes into estrus again.
15. Effects of Human Pheromones.
• At puberty, pheromones derived from androgens act as
sexual attractants. E.g. found that non-pill using females
unknowingly exposed to male pheromones gave higher
attractiveness ratings to photographs of males faces.
men smelled T-shirts of young women who were either
near ovulation or far from it. In two studies, the men also
smelled unworn T-shirts, which served as controls.
men who sniff the ovulation-scent display higher levels of
testosterone than otherو testosterone effects are large
enough to produce changes in behavior
man is more likely to be attracted to an ovulating female
and to pursue her as a partner
The effect of women ovulation- scent on man
• follicular phase images were more
attractive approximately 54% of the time.
Similarly, relative to those from other cycle
phases
• women's sexual desires vary across the
cycle found that women's ability to
categorize male faces and male
stereotypic words is faster near ovulation,
suggesting increased attentiveness to
maleness at high fertility.
Subtle ovulatory cues in women
16. 0%
5%
10%
15%
20%
Japanese faces Caucasian faces
%
feminization
preferred
low conception risk
high conception risk
Significant effect of conception risk
More interest in sex? Fantasies
Clothing preferences
Gait
Topless dancer study
Do women advertise fertility?
women typically show stronger psychological responses to
attractive men around the time of ovulation
non-fertile women experienced an increase only in cortisol to the
“attractive man .
”
non-fertile women were more attracted to “faithful ”men than were
fertile women
17. Major communication systems in the
body. Integrate stimuli and
responses to changes in external
and internal environment. Both are
crucial to coordinated functions of
highly differentiated cells, tissues
and organs .Unlike the nervous
system, the endocrine system is
anatomically discontinuous
Endocrine vs. Nervous System
18. Another example, the sight of a territorial intruder
may elevate blood testosterone concentrations in
resident male birds and thereby stimulate singing
or fighting behavior. Similarly, male mice or rhesus
monkeys that lose a fight decrease circulating
testosterone concentrations for several days or
even weeks afterward. Comparable results have
also been reported in humans. Testosterone
concentrations are affected not only in humans
involved in physical combat, but also in those
involved in simulated battles. For example,
testosterone concentrations were elevated in
winners and reduced in losers of regional chess
tournaments.
Direct involvement
People do not have to be directly involved in a
contest to have their hormones affected by the
outcome of the contest. Male fans of both the
Brazilian and Italian teams were recruited to provide
saliva samples to be assayed for testosterone before
and after the final game of the World Cup soccer
match in 1994. Brazil and Italy were tied going into
the final game, but Brazil won on a penalty kick at
the last possible moment. The Brazilian fans were
elated and the Italian fans were crestfallen. When
the samples were assayed, 11 of 12 Brazilian fans
who were sampled had increased testosterone
concentrations, and 9 of 9 Italian fans had decreased
testosterone concentrations, compared with pre-
game baseline values
Indirect involvement
19. Phase 1: Being in love
• “Being in love” is the first phase in a
relationship. This phase is characterized by
high passion, a rapid rise in intimacy. This
phase lasts relatively short, usually around
half a year.
• Love during this phase has the character of
excitation and stress.Stress is caused by
insecurity and can lead to mood changes.
• cortisol levels are elevated during this
phase
• follicle stimulating hormone (FSH) and
testosterone levels are downregulated.
• Both changes are typical for stressful
situations
• low serotonin levels PEA Dopamin Serotonin
Cortisol Noradrenalin
Phenylethylamine
Like any other emotion, love is regulated by endocrine factors.
cortisol and other stress hormone
oxytocin
Vasopressin
dopamine
serotonin
testosterone
20. Phase 3: Companionate love
• The phase of passional love usually lasts
several years before evolving into
companionate love. This phase is
characterized by a decrease in passion,
whereas intimacy and commitment remain
high
• oxytocin and vasopressin are thought to be
the dominant hormones, reinstating and
maintaining pair-bonds between the couple
دلبستگی
Lust
After several months to a year the initial phase of
euphoria, excitation, and stress evolves into a phase of
“passional love” which is dominated by feelings of
safety, calm, and balance evels of several
neuroendocrine factors
found to be abnormal in early romantic love, including
NGF , platelet serotonin transporter , and abnormalities
in the HPA-axis have by this time returned to normal.
In this second phase, passion remains high,
Stress is decreased,
oxytocin and vasopressin are believed to be the major
factors during this phase because they are involved in
the formation of strong pair-bonds between the couple
Phase 2: Passione love
وازوپرسین توسین اکسی
Passione
21. LOVE
dopamin
e
serotoni
n
noradre
naline
corti
sol
Phenylet
hylamine
عشق
رمانتیکی
LOVE
antidepressant ,against polygamy,
produced from phenyl alanine in the
brain and found in chocolate
obsessive-compulsive disorder less
serotonin
serotonin dopamin
Cortisol increase due to stress ,fear …
Cortisol levels were significantly higher amongst those subjects who had recently
fallen in love, as compared with those who had not.
The increased cortisol are suggestive of the ‘‘stressful’’ and arousing conditions
associated with the initiation of a social contact.
we have to consider that cortisol levels are difficult to measure since they show
sensible and variant patterns that differ over day and night and between individuals
experiencing different levels of stress.
Epinephrine: person responds
to love with their entire body
epinephrine is released, in the
early stages. sweating, the
dilated pupils, the increased
heart rate, is exactly how people
describe the feeling and energy
of being “in love”.
22. Maternal love
prolactin, and endogenous opioids, oxytocin reduces HPA axis (re)activity and it further
reinforces the attachment between mother and child, Interestingly, milk contains high levels of
them.
• Animal studies have demonstrated that the neuropeptides Prolactin and Oxytocin act as
important components of the neurobiological pathways underlying the initiation and
maintenance of maternal behavior
• Men and women exhibit elevated levels of plasma PRL concentrations prior to childbirth as
compared to the post-natal
• Furthermore, an increase in OT levels from the first to the third trimester of pregnancy was
found to predict greater maternal bonding to her fetu
PRL and OT are considered as important components of the
neuroendocrinology of fatherhood and were each associated with a
specific aspect of paternal behavior:
PRL with father facilitation of the child's exploratory
behavior and OT with the father–infant Affect Synchrony
23. Paternal love
• men who thought their wives had a more positive opinion of them
as caregivers experienced a greater drop in PRL when interacting
with their children compared to men who thought their spouses
viewed them less positively
• Fathers with more lifetime experience caring for children have been
found to have lower CORT
• while baseline CORT has been shown to be lower in partnered
fathers compared to single non-fathers
• CORT appears to peak in the weeks before their partners' give birth,
then falling off drastically post-partum
• fathers who were more involved in day-to-day caregiving tended to
have greater short-term declines in PRL after playing with their child
compared to fathers who participated less in routine childcare
• Fathers with higher PRL concentrations were more positive and alert to their
infant cues.
• PRL decreased when fathers were exposed to their firstborn infant's cry or held
the infant in their arms for the first time.
• PRL levels increased after the same fathers held their second newborn
• While fathers listening to their infants' cries, experienced fathers showed a
greater increase in PRL as compared to first-time fathers
24. the role of OXT in affiliative behavior in animals is pair bonding in prairie voles (Microtus ochrogaster).
These voles are relatively unique in their monogamous social structure, which is mediated by OXT and
AVP activity in the brain. Central OXT infusions facilitate prairie vole pair bonding, which has been
linked to gender specific developmental effects in male voles. The distribution of OXT receptors in the
brain mediates divergent social strategies in monogamous and polygamous vole species. OXT actions
on social behavior are mediated by changes in recognition and social memory. In male rats, OXT
facilitates sexual behavior through actions in the PVN. In pair bonded tamarin monkeys, peripheral OXT
levels vary with levels of affiliation and sexual behavior in both genders. Specifically, OXT levels in male
tamarins were correlated strongly with sexual behavior. In fish it has been postulated that isotocin (the
teleostean homologue of OXT) is involved in courtship displays and territorial defense, and many of the
social behavior effects of OXT are conserved across taxa.
Intranasal OXT promotes trust and prosocial behaviors which are critical to human bonding and it is
also associated with trustworthiness. Intranasal OXT increases cooperation following unreciprocated
cooperation in a social experiment and this behavioral effect was associated with increased fMRI activity
in OXT regions associated with affiliation. Effects of OXT are often mediated by direct physical contact
as increased plasma OXT has been recorded in men during social contact with a partner, and during
orgasm.
Impaired affiliation has been associated with decreased plasma OXT in autistic patients. Normal
affiliative expression is especially impaired in autistic males, and some autistic males have deficits in
OXT receptor expression. Several cases were associated with hypermethylation of the OXT receptor
gene and a decrease in OXT receptor mRNA. Furthermore, clinical studies have reported enhanced
social interactions (eye contact, social memory) in autistic patients following intranasal OXT. Several
labs have investigated the use of OXT for the treatment of social behavior deficits in autism and social
anxiety disorder, and research in this area is ongoing.
25. OXT and male aggression
OXT has inhibitory effects on aggression.
Conversely, some have postulated that OXT’s
anxiolytic effects could result in increased
aggression, but there are no behavioral data in
support of this theory. One potential clinical role
of OXT is in the treatment of PTSD associated
aggression.
Affiliative actions of OXT in vertebrates are
associated with aggression. OXT levels are
highest in male sticklebacks that aggressively
defend eggs and in subordinate males that fight
to change their social status. Disruption of the
OXT gene in male mice decreases aggression,
yet OXT knockout mice display elevated
aggression which is postulated to be the result
of decreased fearfulness. One potential
explanation for this inconsistency is indirect
effects through AVP due to the neuroanatomical
and biochemical similarities between the two
neuropeptide systems. The increased aggression
in OXT knockout mice may be mediated by a
compensatory increase in AVP in these males.
OXT mediates the establishment and support of social bonds in
several female mammalian species. Central injection of OXT
specifically facilitates pair bonding in female prairie voles. The role of
OXT in female rodent affiliation may be related to its effects on
maternal behavior. In primates, affiliation has been correlated with
urinary OXT levels, including a relationship between the solicitation
of sex and increased OXT levels.
OXT levels in females rise during massage, genital stimulation,
copulation, and orgasm which parallels the association between OXT
and physical contact in men. In a study of intrapersonal couple
conflict, intranasal OXT increases positive communication and
decreases plasma cortisol. It is suggested that OXT may facilitate
pair bonding in humans, as in voles. Women with more supportive
partners have increased OXT before, during, and after a 10 minute
period of physical contact. In contrast, OXT is positively correlated
with interpersonal conflict, but the relevance of these changes in
OXT is debated. This increase in OXT may be in response to the
conflict and not a causal factor. Some have speculated that plasma
OXT may be a reliable biomarker of distressed relationships in
female humans. Intranasal OXT alters the neural response to
emotional faces in women, and these effects differ from the effects in
males. One hypothesis is that OXT increases as a mechanism to
ameliorate the negative effect of the conflict on the social bond, but
further manipulative studies are needed in this area.
OXT and female affiliation
26. Oxytocin
and
vasopressin
serotonin
dopamine
plasma OT levels were significantly higher in new lovers as compared
to new parents and singles, suggesting increased activity of the OT
system when falling in love.
OT administration increased couples' positive communication and
plasma OT was related to positive communication, affiliation, and
emotional support between partners
The Hypothalamic pituitary adrenal axis (HPA axis) is under the
influence of oxytocin and vasopressin
vasopressin could potentially play a role in increased HPA axis
activity in the early stages of romantic love
it is likely that oxytocin contributes to the decreased stress levels and
HPA axis activity seen in long-term relationships
Vasopressin injection to male rates will
Couse more bounding between the rates
27. Central OXT decreases anxiety in pregnant and lactating rats,
despite having no effect in virgins. chronic icv OXT is anxiolytic in
female rats selected for high levels of anxiety. ovariectomized rats
indicate that circulating estrogen is required for the anxiolytic
effects of OXT, which is likely to involve dynamic estrogen
dependent changes in OXT receptor levels. This dependence on
estrogen may explain the divergent results in maternal and
nulliparous rats considering the robust hormonal changes of
pregnancy and lactation. Elevated plus maze (EPM) testing
indicates that the anxiolytic effects of OXT may be most potent in
stressful context, as OXT is only anxiolytic when the EPM is
presented as a novel environment. These data are relevant to the
clinical observation that exposure to stress is a significant
predictor of depression in females. plasma OXT is difficult to
measure and has a high degree of variability, reduced plasma OXT
has been documented in both males and females suffering from
depression. Changes in the variability of OXT pulses have also
been reported in women with major depression. There are
neuroendocrine differences in the role of OXT and AVP in human
depression. Studies of maternal humans suggest that OXT may be
specifically involved in the development of postpartum mood
disorders. Women with lower plasma OXT while interacting with
their own infants are at an increased risk for depression due to low
attachment ratings as adults and low attachment ratings for their
children. Cocaine addicted mothers, who are at an increased risk
for postpartum mood disorders which result in impaired maternal
infant attachment also have depressed plasma OXT levels.
Childhood trauma, which is a reliable predictor
of adult depression, has been associated with
decreased CSF OXT and high levels of anxiety.
Both prior stressful events and current exposure
to stress are significant predictors of postpartum
depression, so the association between stress
and OXT may be involved in a common
mechanism for the development of postpartum
mood disorders. Low plasma OXT during
pregnancy predicts an increased risk for
postpartum depression and elevated OXT in
postpartum women is associated with low levels
of anxiety. The advantage of targeting clinical
studies of OXT and depression at postpartum
depression is that improvements in these
patients is also beneficial to the rest of the
family, and may represent a preventative target
for the offspring of depressed mothers. Failed
lactation and perinatal depression have related
neuroendocrine mechanisms. Failed lactation is
common in depressed mothers, and in many
cases can exacerbate symptoms of depression
in mothers.
OXT in female animal models of depression and anxiety
28. OXT and female human learning and memory
Social bonds require memory related components of
social recognition. OXT’s role in bonding involves social
recognition and memory mechanisms. Studies from male
subjects suggest that despite a potential amnesiac
function of OXT in certain paradigms, central OXT may
enhance social memory. It is unknown whether OXT has
similar effects in women.
The disruption of endogenous OXT activity impairs short-
term olfactory memory in female rats, and mice with a
conditional OXT knockout display impairments in social
recognition. In sheep, a functioning OXT circuit in the
olfactory bulb is required for offspring recognition. These
effects of OXT on offspring recognition are mediated by
GABA, norepinephrine, and acetylcholine and are crucial
to the role of OXT in maternal care induction. Effects of
OXT in pair bonding involve a social recognition function.
Central OXT is involved in the consolidation of maternal
memory. One hypothesis is that the effects of both OXT
and AVP are mediated by their actions on dopamine.
Although some studies of ongoing maternal care
conclude that OXT is not necessary once offspring care
has been established, these data on maternal memory
indicate that its importance to maternal care may extend
beyond the initial stages of maternal care.
Intranasal OXT facilitates socially reinforced learning and
emotional empathy OXT’s effects were specific to the social
stimuli of facial expressions, and did not affect financial
associations in an associative learning task. OXT facilitates social
reinforced learning and memory in human males, and these
effects may be mediated at the amygdala.
Most of the research on OXT and learning and memory has been
limited to male models . OXT mediates social recognition in
several species, and male OXT knockout mice exhibit social
amnesia, while other forms of memory are not affected. This
effect on social recognition is reversed by OXT treatment and is
mediated by the transmembrane protein CD38. A single dose of
OXT can specifically impair memory retention, and further study
indicates that exogenous OXT inhibits cholinergic mechanisms
that are necessary for memory retention. Another mechanism
implicated in the amnesiac effects of OXT is glucocorticoid
release, as dexamethasone is able to reverse the effects of OXT
on memory. While OXT may facilitate memory and social
interactions in certain contexts such as pair bonds at certain
levels, robust levels of OXT may impair social memory due to
substantial glucocorticoid release or impaired cholinergic activity.
