1. Male and Female Brain-
What constitutes the gender
difference Dr Supriya Hegde Aroor
Associate Professor
Dept of Psychiatry
KMC Mangalore
2. Have you ever felt it so?
• Why men & women think differently?
• Why they behave differently in stressed
situations?
• Why they excel at different types of tasks?
• Why do boys like to play with cars and
trucks and superman?
• Why there are sex differences in some
diseases?
4. Anatomical differences
• Weight - Around 1130 cm3in Women and
1260 cm3 in Men.
• Male brains are about 10% larger than
female brains.
• Men's heads are also about 2% bigger than
women's.
• Even in early development a boy’s brain is
between 12-20% larger than that of a girl.
• Head circumference of boys is also 2% larger
than that of girls.
6. Grey v/s White Matter
• Grey matter- Men have approximately 6.5
times more grey matter than women.
• White matter- Women have about 10
times more white matter than men.
• Women have more of the white matter
responsible for communication.
• So, women have greater ability to do
multitask.
7. Hypothalamus
• Preoptic area - 2.2 times larger in men than
in women and contains 2 times more cells.
• Suprachiasmatic nucleus – In males it is
shaped like a sphere whereas in females it is
more elongated.
• The strongest sex difference is found in the
lateral and medial mamillary nucleus.
• Differences also in Androgen Receptors in
various areas.
8. Cerebral Hemispheres
Male Brain
• Enlarged frontal and
occipital poles.
• Thicker Right
hemisphere.
• Have a greater
functional reserve.
• Have larger
Cerebellum.
Female Brain
• Greater cortical
thickness in Temporal &
Parietal regions
• Thicker Left
hemisphere.
• More Neuropil.
• Larger Anterior
commissure & Mass
Intermedia.
9. Other areas which are larger…
Male Brain
• Inferior Parietal Lobule (Lt
> Rt in Rt handed male).
• Amygdala.
Female Brain
• Orbitofrontal to Amygdala
Ratio.
• Limbic System.
• Corpus Callosum.
• Straight Gyrus.
• Hippocampus.
• Broca’s & Wernick’s area.
• Lateral Ventricles (Lt >
Rt).
10. Functional differences
• Men & Women differ in
the way they think !!!...
• They differ in use of
different parts of the
brain to encode
memories, sense
emotions, recognize
faces, solve certain
problems and make
decisions.
12. Functional differences
Male Brain
•
•
•
• Predominantly hard-wired
for understanding &
building systems.
Value more for power,
politics, and competition.
When listening neurons
on only one side of the
brain are activated.
In interpretation of whole
sentences, men use one
side of brain.
•
•
•
Female Brain
• Predominantly hard-wired
for empathy.
Value the development of
altruistic, reciprocal
relationships.
While listening neurons
on both sides of the brain
are activated.
In interpretation women
use both sides of the
brain.
13. Functional differences
Male Brain
•
•
• In stress, Increased blood
flow to the right prefrontal
cortex, responsible for
“fight or flight”.
Men tend to be more
logical emotionally.
Men navigate by using
abstract concepts such
as north and south or
distances.
•
•
Female Brain
• There is increased blood
to limbic system, which is
associated with nurturing
& friendly response.
Women tend to be more
observant
Women navigate by
talking about landmarks
and things that can be
seen or heard.
14. Functional differences
Male Brain
•
•
• In play, Engage in more
rough-and tumble play.
Aggression, show more
“direct” aggression such
as pushing, hitting &
punching.
Better at visual spatial
abilities, quantitative
problem solving, mental
rotation and spatial
perception.
Female Brain
• Engage in more nurturing
games.
• Show more “indirect”(or
“relational” ) aggression.
• Better in verbal memory
tasks, verbal fluency
tasks & in speed of
articulation.
15. Functional differences
Male Brain
• Tend to be better in
independence,
dominance, spatial &
mathematical skills, rank-
related aggression. •
•
Female Brain
• Show greater concern
through more sad looks,
sympathetic vocalizations
and comforting.
Women were observed to
show more comfort, even
to strangers.
Can think logically and
emotionally at the same
time.
16. Do men & female differ in expression of emotions?
17. Emotions
• Women
– Faster and more accurate at identifying emotions.
– Better at controlling their emotions.
– More adept in encoding facial differences &
changing vocal intonations.
– Part of brain involved is large.
– Use both hemispheres.
• Men
– Right hemisphere deals with emotions.
– Males have a hard time expressing emotions.
18. Biochemical differences
• Biochemically heterogeneous in regard to
sex and brain region.
• Seen mainly in the sensorimotor cortex
and orbital frontal cortex.
• Functional brain studies indicate sex
differences in brain metabolism.
19. Sensorimotor cortex
• Involved in sensory and motor processing,
perception, and motor execution.
• In female brain, increased NAA (N-acetyl
Aspartate) is found.
• NAA is localized within the neurons & is
involved in synaptic processes. It can be
considered a neuronal & axonal marker.
20. Functional brain studies
• Cognitive activity resulted in increased
blood flow to the cerebral hemispheres.
• For Verbal task- Left hemisphere.
• For Spatial task- Right hemisphere.
• Men
– Higher glucose metabolism - temporal-limbic
regions and cerebellum.
– Lower glucose metabolism - cingulate
regions.
21. Serotonin
• Function - Involved in gender-related
behaviours and psychiatric conditions like
aggression, eating disorders, depression,
impulsivity or suicide.
• Males
– Synthesis is 52% higher than in females.
–Higher 5 HT2receptors, esp. in frontal & cingulate
cortices.
• Females
– Higher 5 HT 1A receptors.
• Importance – differences in prevalence of
depression & anxiety.
22. Differences in Neurotransmitter
systems
• Receptor affinity of glucocorticoids in females
is half than in males.
• Differences are reported in biochemical
pathways pertaining to dopamine, and the
interactions between them.
• Women have a greater presynaptic dopamine
synthesis and a lower D2 receptor affinity.
• Women also have lower amphetamine-
stimulated dopamine release and a greater
dopamine transporter uptake.
23. Differences in Neurotransmitter
systems
• Women appear to have elevated basal, but
decreased stimulated, striatal dopamine levels.
• Levels of monoamine oxidase were significantly
higher in several brain regions in women.
• Genetic associations between COMT and various
Psychiatric phenotypes frequently show
differences between men and women.
• Importance - May contribute to differential
involvement in psychiatric disorders in men and
women.
24. Differences in Brain Maturation &
Aging
• The brains of men and women are indeed
different from birth.
• But differences are subtle & might be found
only among the synapses in brain structures.
• MRI analysis suggest that females brain
mature earlier than male brain.
• Males age 6-17 years have been shown to
display more prominent age-related
decreases in grey matter and increases in
white matter than females.
25. Differences in Brain Maturation &
Aging
• Adolescents’ brains undergo a substantial
“pruning” or reduction in grey matter volume,
this happens 2yrs earlier in females.
• Girls reach puberty two years earlier than
boys.
• Prefrontal cortex develops earlier in girls
compared to boys.
• Areas of the brain involved in language and
fine motor skills mature about six years
earlier in girls than in boys.
26. Differences in Brain Maturation &
Aging
• Brain volume decreased with age among
men, but hardly at all among women.
• Greater decrements in brain volume occur
with age in the frontal lobe than in the
temporal lobe and in both regions it is
greater in men.
• Women are less vulnerable to age related
changes in mental abilities.
27. Causes…. Genetic
•
•
•
•
Genes on the sex chromosomes determine the gender
of the brain in two ways
– Acting on the gonads to induce sex differences in levels of
gonadal secretions that have sex-specific effects on the brain.
– Acting in the brain itself to differentiate XX and XY brain cells.
Various studies performed identified different genes
whose expression differed between male and female
brain.
Two candidate genes are the two testis-determining
factors (ZFY) and the master switch for differentiation of
a testis SRY.
It was shown that SRY and ZFY are transcribed in the
hypothalamus and frontal and temporal cortex of male.
28. Causes…. Sex hormones
• During the development of the embryo in the
womb, circulating hormones have a very
important role in the sexual differentiation of
the brain.
• The presence of androgens in early life
produces a “male” brain. In contrast, lack of
androgens causes female brain.
• Levels of circulating sex steroid hormones,
during development and in adulthood, play a
critical role in determining physiology and
behaviour in adulthood.
29. Causes…. Evolution
•
•
•
•
Neurological substrate that forms the basis for
complex cerebral asymmetries in Homo sapiens may
have been established remarkably early in anthropoid
evolution.
In ancient times, both sexes had very defined role that
helped ensure the survival of the species.
Brain areas may have been sharpened to enable each
sex to carry out their jobs.
Developing superior navigation skills in men may be
better suited to the role of hunter, while preference for
landmarks in female may have enabled them to fulfil
the task of gathering food closer to home.
30. Causes…. Culture &
Socialisation
• Sex-determined differences appear in infancy
and the gap widens as people mature.
• Sex differences that grow larger throughout
childhood are probably shaped by culture,
lifestyle and training.
• Studies on brain plasticity have shown that
experiences changes brains structure.
• During development synapses that are not
used are eliminated. This is where
experience plays an important role in wiring a
young child's brain.
31. Susceptibility to Psychiatric
Disorders
• Many CNS-related disorders show sex
differences in their incidence and/or nature.
• Females have higher predisposition of
Alzheimer's disease, Addiction, Major
depressive disorder, Anxiety, Post-Traumatic
Stress Disorder, Eating disorders.
• Males have higher predisposition for Autism
spectrum disorders, ADHD, Schizophrenia.
32. Susceptibility to Psychiatric
Disorders
• Also it is noticed that men with schizophrenia
show significantly larger ventricles, whereas no
such enlargement is seen in women with
schizophrenia.
• Symptoms of depression significantly increase the
risk of developing AD in men, but not in women.
• There is evidence that Rt hemisphere PFC lesions
impair performance on decision-making task in
men but not women, whereas Lt hemisphere
lesions impair performance in women but not men.
33. Susceptibility to Psychiatric
Disorders
•
•
•
•
Females are more sensitive to reinforcing effects of
psychostimulants which account for rapid progression
from initial use to drug dependence.
Different types of head injuries are more disastrous to
one sex or the other. For e.g. frontal lobe injuries can
be more detrimental to cognitive performance in
women than men.
For stroke a woman may have rehabilitation options
that the man may have more trouble, because the
woman may be able to perform tasks using the other
side of her brain.
Men may have more trouble with rehabilitation & may
need to be checked more carefully before he can
resume daily activities.
34. Conclusion
• Male & Female brains show anatomical, functional
and biochemical differences in all stages of life.
• Sex differences need to be considered in studying
brain structure and function.
• Helps in in early diagnosis, precise treatment and
management for neurological & psychiatric
diseases.
• Understanding development of normal brain and
differences between the sexes is important for the
interpretation of clinical imaging studies.
