Transcript Sex & The Brain

Let’s Talk About Sex, Baby
Why? Because babies making funny faces is
freakin’ hilarious… That’s Why
First things first…
https://www.youtube.com/watch?v=U5xkxTfVLSA
Male vs. Female
• There are significant differences in brain
structure between male and female
– Slight differences in the brain anatomy of
men and women.
• On average, women’s brains are smaller.
But…
• Size is not the key
however
• Number of neurons is
more critical
– On average, women
have 11% more
neurons
– “Extra” neurons are
found in 2 layers of
cerebral cortex
• recognition of
language, melodies,
and tone of voice
The Corpus Callosum
• Neural bridge connecting right and left hemispheres
– Best documented anatomical difference
• Larger in women than in men
• Researchers from UCLA examined 146 cadavers
– Rear portion up to 23% larger in women than
in men
• Are women better able to integrate the left and right
brain?
– Unknown, not demonstrated to date
– Significant only if it contained more neurons
Sex Hormones and Development
• The most important factor in differentiation of
males and females and in differentiating
individuals within a sex is the level of
exposure to various sex hormones early in life
• Sex hormones can stimulate or repress the
development of neurons
• The brain of a developing fetus is bathed in
sex hormones
• At birth, environmental & cultural factors are
acting on the already differently wired brains
of boys and girls.
Say What?!
The Role of
Testosterone
• Testes produce male
hormones, or androgens
– Testosterone
– Organize development and
male behaviors early in life
• Female anatomy (and
most “feminine” behavior)
is the default mode in the
absence of androgens
The Effect of Hormones is Life-altering
• Effects of early exposure to sex hormones
are lifelong
• Changes are 'organizational'
• Alter brain function permanently during a
critical period in prenatal or early postnatal
development.
• Administering the same sex hormones
later in development or in the adult has no
similar effect
Animal Studies
• A male rodent deprived of androgens
immediately after birth (by castration or by a
drug that blocks androgens)
– Male sexual behavior is reduced, and female
sexual behavior is expressed.
Animal Studies
• If androgens are administered to a
female directly after birth, she will
display more male sexual behavior and
less female behavior in adulthood
Hate cats, but that’s
stinkin’ hilarious
Human Studies
• Controlled experiments in humans
are not ethically feasible
– Scientists have studied defects
which affect hormone levels
• Boys with a syndrome that
makes them insensitive to
testosterone are better at
language than their unaffected
brothers, but they are less
adept at spatial tasks
CAH & DES in Girls
• The birth defect, CAH causes production of high
levels of testosterone during fetal development in
girls.
– CAH girls score better on spatial and mathematical tests
• Girls exposed to the hormone DES in utero (a drug
given to prevent miscarriage) are also exposed to
excess testosterone.
– DES girls are entirely feminine in all other respects.
– DES girls do better than their normal sisters in spatial and
mathematical tasks
The Role of the Hypothalamus
• Regulates reproductive behavior
• Connects to the pituitary (master endocrine)
gland
• One region of the hypothalamus is visibly larger
in male rats than in females
– this size difference is under hormonal control.
• Scientists have also found parallel sex
differences in a clump of nerve cells in the
human brain
– parts of the interstitial nucleus of the anterior
hypothalamus are larger in men than in women
The Hypothalamus & Sexual Orientation
• Sexual orientation and gender identity
have been related to anatomical
variation in the hypothalamus
Male Dominated Tasks
• On average, men perform better than
women in spatial tasks
– Tests that require the subject to imagine
rotating or manipulating an object
– Navigating through a route
• More accuracy in tests of target-directed
motor skills--that is, in guiding or
intercepting projectiles
• Better at mathematical reasoning tests
• They do well on tests that involve
mentally rotating an object or
manipulating it in some fashion, such as
imagining turning this three-dimensional
object
• Or determining where the holes punched
in a folded piece of paper will fall when
the paper is unfolded:
• Men also are more accurate than women
in target-directed motor skills, such as
guiding or intercepting projectiles:
• Men do better on disembedding tests,
in which they have to find a simple
shape, such as the one on the left,
once it is hidden within a more
complex figure:
• And men tend to do better than women
on tests of mathematical reasoning:
Female Dominated Tasks
• Women, on average, excel in language tasks:
– tests that measure recall of words
– tests to find words that begin with a specific letter
or fulfill some other constraint.
• Women are better than men at rapidly
identifying matching items
• Women also excel at certain precision
manual tasks
• Women tend to perform better than
men on tests of perceptual speed, in
which subjects must rapidly identify
matching items for example, pairing the
house on the far left with its twin:
• Women remember whether an object,
or a series of objects, has been
displaced:
• Women outperform men on tests of
ideational fluency, for example, subjects
must list objects that are the same color.
• Women also outperform men on tests of
verbal fluency, in which participants must
list words that begin with the same letter.
• Women do better on precision manual
tasks-that is, those involving fine-motor
coordination - such as placing the pegs in
holes on a board:
• Women do better than men on
mathematical calculation tests:
Who Needs Directions?
• Studies show that men complete a computer
simulation of a maze or labyrinth task more quickly
and with fewer errors than women do.
• A different study used a path on a tabletop map to
measure route learning.
– Although men learned the route in fewer trials and with
fewer errors, women remembered more of the
landmarks, such as pictures of different types of
buildings, than men did.
• Women use landmarks as a strategy to orient
themselves in everyday life more than men do.
Landmark Memory
• Research suggests that women have superior
landmark memory
• Researchers tested the ability of individuals to
recall objects and their locations within a confined
space, such as in a room or on a tabletop
– Women were better able to remember whether items
had changed places
• Other investigators found that women are superior
at a memory tasks such as remembering the
location of pictures on cards turned over in pairs
• At this kind of object location, in contrast to other
spatial tasks, women have the advantage
Lost your keys?
• Don’t be proud, just ask your wife
where you put them last…
The Evidence from PET & FMRI
• Positron emission tomography (PET) & functional
magnetic resonance imaging (FMRI) can reveal
how male & female brains actually function.
• By detecting areas of the brain using the most
blood glucose, PET pinpoints active regions.
– Glucose is the basic fuel of all cells in the body, including
brain cells.
– Thus, active regions of the brain use more glucose than
quiescent areas.
– Glucose is radio-labed
– The brain areas in use then will emit more radioactivity,
which can be detected by the PET scan.
Your Brain is the Largest Sex
Organ you have
Even though it may
seem strange, the
vast majority of sex
occurs in the brain
Can 10,000 Men Be Wrong?
 Cleveland
Clinic Study
 Asked
10,000 men one question
 “Does
your wife show you her love?”
 Men
who answered yes, lived
statistically, significantly longer than
the men who answered no!
 Your
life may depend on your love life
Hormones of

Love
Epinephrine – Typically increases

Makes your heart flutter and
you get those butterflies in
your stomach (really excited to
see them!)

Go to a scary movie so she’ll
get scared and cling to you
Or be a big pansy and
hide behind her instead…
That’s weak, bro
More pictures of folks getting
scared outta they minds
Best BF ever…
Look at that face!
No fear, staring it
down son!
OG of the Haunted
House right there
• Totally
unphased
Don’t worry
babe, I got
this…

Dopamine – Triggers the reward systems in the brain

Increases with novelty (when things are new and
fresh = exciting and awesome)

Makes you want to be with them all the time, obsess
over them and always thin about them

Serotonin – I can’t stop thinking of you

Lowers in people who are newly in love

You’re crazy about them… literally

Low serotonin levels are also found
in those that have OCD (that’s why you’re so obsessive)

Oxytocin – the “cuddle” hormone

Released when people touch (sexually or non-sexually)

Gives you that sense of trust, security and attachment

Responsible for the intense bond b/w a mom and her
baby
Dopamine
Serotonin
Norepinephrine
Science of Love and Heartbreak
The Science behind Love
https://www.youtube.com/watch?feature=player_de
tailpage&v=sU7lpX6dvF8
https://www.youtube.com/watch?feature=player_de
tailpage&v=EJaY0pOdJfY#t=29
The Science Behind Heartbreak
https://www.youtube.com/watch?v=lGglw8eAikY