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Chapter 2
The Biology
of Mind
© 2013 Worth Publishers
Surveying the Chapter: Overview
What We Have in Mind
 Building blocks of the mind: neurons
and how they communicate
(neurotransmitters)
 Systems that build the mind: functions
of the parts of the nervous system
 Supporting player: the slowercommunicating endocrine system
(hormones)
 Star of the show: the brain and its
structures
Searching for
the biology of
“self”
Is our identity in the
heart? In the
brain? In the whole
body?
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Searching for the self by studying the body
Phrenology
Phrenology
(developed by Franz Gall in
the early 1800’s):
the study of bumps on the
skull and their relationship
to mental abilities and
character traits
 Phrenology yielded one big idea-that the brain might have
different areas that do different
things (localization of function).
Today’s search for the biology of the self:
biological psychology
 Biological psychology
includes neuroscience,
behavior genetics,
neuropsychology, and
evolutionary psychology.
 All of these
subspecialties explore
different aspects of:
how the nature of mind
and behavior is rooted in
our biological heritage.
 Our study of the biology
of the mind begins with
the “atoms” of the mind:
neurons.
Neurons and Neuronal Communication:
The Structure of a Neuron
There are billions of neurons
(nerve cells) throughout the body.
Action potential:
a neural impulse that travels down an
axon like a wave
Just as “the wave” can flow to
the right in a stadium even
though the people only move
up and down, a wave moves
down an axon although it is
only made up of ion exchanges
moving in and out.
When does the cell send
the action potential?...
when it reaches a
threshold
The neuron
receives
signals from
other
neurons;
some are
telling it to
fire and some
are telling it
not to fire.
 When the
threshold is
reached, the
action potential
starts moving.
 Like a gun, it
either fires or it
doesn’t; more
stimulation does
nothing.
 This is known as
the “all-ornone” response.
The threshold is reached when
excitatory (“Fire!”) signals
outweigh the inhibitory (“Don’t
fire!”) signals by a certain amount.
How neurons communicate
(with each other):
The action
potential
travels down
the axon
from the cell
body to the
terminal
branches.
The signal is
transmitted
to another
cell.
However, the
message
must find a
way to cross
a gap
between
cells. This
gap is also
called the
synapse.
The Synapse
The synapse is a
junction between the
axon tip of the
sending neuron and
the dendrite or cell
body of the receiving
neuron.
The synapse is
also known as the
“synaptic
junction” or
“synaptic gap.”
Neurotransmitters
Neurotransmitters
are chemicals
used to send a
signal across the
synaptic gap.
Reuptake:
Recycling Neurotransmitters [NTs]
Reuptake:
After the neurotransmitters
stimulate the receptors on
the receiving neuron, the
chemicals are taken back up
into the sending neuron to
be used again.
Neural Communication:
Seeing all the Steps Together
Roles of Different Neurotransmitters
Some Neurotransmitters and Their Functions
Neurotransmitter Function
Problems Caused by Imbalances
Serotonin
Affects mood, hunger,
sleep, and arousal
Undersupply linked to depression;
some antidepressant drugs raise
serotonin levels
Dopamine
Influences movement,
learning, attention, and
emotion
Oversupply linked to schizophrenia;
undersupply linked to tremors and
decreased mobility in Parkinson’s
disease and ADHD
Acetylcholine
(ACh)
Enables muscle action,
learning, and memory
ACh-producing neurons deteriorate as
Alzheimer’s disease progresses
Norepinephrine
Helps control alertness
and arousal
Undersupply can depress mood and
cause ADHD-like attention problems
GABA (gammaaminobutyric acid
A major inhibitory
neurotransmitter
Undersupply linked to seizures,
tremors, and insomnia
Glutamate
A major excitatory
neurotransmitter;
involved in memory
Oversupply can overstimulate the brain,
producing migraines or seizures; this is
why some people avoid MSG
(monosodium glutamate) in food
Serotonin
pathways
Networks of neurons that
communicate with serotonin
help regulate mood.
Dopamine
pathways
Networks of neurons that
communicate with dopamine are
involved in focusing attention
and controlling movement.
Hearing the message
How Neurotransmitters Activate
Receptors
When the
key fits,
the site is
opened.
Keys that almost fit:
Agonist and Antagonist Molecules
An agonist molecule fills
the receptor site and
activates it, acting like the
neurotransmitter.
An antagonist molecule
fills the lock so that the
neurotransmitter cannot
get in and activate the
receptor site.
The Inner and Outer Parts of the
Nervous System
The central
nervous
system
[CNS]
consists of
the brain
and spinal
cord.
The CNS
makes
decisions
for the
body.
The
peripheral
nervous
system [PNS]
consists of
‘the rest’ of
the nervous
system.
The PNS
gathers and
sends
information
to and from
the rest of
the body.
Types of Neurons
Sensory
neurons carry
messages IN
from the
body’s tissues
and sensory
receptors to
the CNS for
processing.
Motor
neurons carry
instructions
OUT from the
CNS out to the
body’s tissues.
Interneurons
(in the brain
and spinal
cord) process
information
between the
sensory input
and motor
output.
The “Nerves”
are not the same as neurons.
Nerves consist of
neural “cables”
containing many
axons.
Nerves are part of
the peripheral
nervous system and
connect muscles,
glands, and sense
organs to the
central nervous
system.
More Parts of the Nervous System
The Peripheral Nervous System
The
Autonomic
Nervous
System:
The sympathetic
NS arouses
(fight-or-flight)
The
parasympathetic
NS calms
(rest and digest)
The Central Nervous System
 The brain is a web of
neural networks.
 The spinal cord is full of
interneurons that
sometimes have a “mind
of their own.”
Neural Networks
These complex webs of interconnected
neurons form with experience.
Remember:
“Neurons that fire together, wire together.”
Interneurons in the Spine
Your spine’s
interneurons trigger
your hand to pull
away from a fire
before you can say
OUCH!
This is an example
of a reflex action.
The Endocrine System
The endocrine system
refers to a set of glands that
produce chemical
messengers called
hormones.
The Body’s “Slow but Sure”
Endocrine Message System
 The endocrine
system sends
molecules as
messages, just like
the nervous system,
but it sends them
through the
bloodstream instead
of across synapses.
 These molecules,
called hormones,
are produced in
various glands
around the body.
 The messages go to
the brain and other
tissues.
Adrenal Glands
produce hormones such as
adrenaline/epinephrine,
noradrenaline/norepinephrine, and
cortisol.
Adrenal Glands
Pancreas
1. The sympathetic
“fight or flight”
nervous system
responds to stress
by sending a
message to
adrenal glands to
release the
hormones listed
above.
2. Effect: increased
heart rate, blood
pressure, and
blood sugar. These
provide ENERGY
for the fight or
flight!
The Pituitary Gland
 The pituitary gland is the
“master gland” of the
endocrine system.
 It is controlled through
the nervous system by the
nearby brain area--the
hypothalamus.
 The pituitary gland
produces hormones that
regulate other glands
such as the thyroid.
 It also produces growth
hormone (especially
during sleep) and
oxytocin, the “bonding”
hormone.
Pituitary gland
The Brain
What we’ll discuss:
 how we learn about the brain
 the life-sustaining inner parts of the
brain: the brainstem and limbic system
 the outer, wrinkled “bark”: the cortex
 left, right, and split brains
Questions about parts of the brain:
 Do you think that the brain is the
sum of its parts, or is the brain
actually about the way they are
connected?
 What do you think might happen
if a particular area of the brain
was stimulated?
 What do you think might happen
if a particular area of the brain
was damaged or not working
well?
Is it possible to
‘understand’ the brain?
“If the human brain were
so simple that we could
understand it, we would
be so simple that we
couldn’t.”
–Emerson M. Pugh
…but we can try.
Investigating the
Brain and Mind:
How did we move beyond
phrenology?
How did we get inside the
skull and under the
“bumps”?
 by finding what happens
when part of the brain is
damaged or otherwise
unable to work properly
 by looking at the
structure and activity of
the brain: CAT, MRI,
fMRI, and PET scans
Strategies for finding out
what is different about the
mind when part of the
brain isn’t working
normally:
 case studies of accidents
(e.g. Phineas Gage)
 case studies of split-brain
patients (corpus callosum
cut to stop seizures)
 lesioning brain parts in
animals to find out what
happens
 chemically numbing,
magnetically deactivating,
or electrically stimulating
parts of the brain
Studying cases of brain damage
When a stroke or injury damages part of the brain, we
have a chance to see the impact on the mind.
Intentional brain damage:
Lesions (surgical
destruction of brain
tissue)
 performed on animals
 has yielded some
insights, especially
about less complex
brain structures
 no longer necessary, as
we now can chemically
or magnetically
deactivate brain areas
to get similar
information
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Split-Brain Patients
 “Split” = surgery in
which the
connection between
the brain
hemispheres is cut
in order to end
severe full-brain
seizures
 Study of split-brain
patients has yielded
insights discussed at
the end of the
chapter
We can stimulate parts of the brain
to see what happens
 Parts of the brain, and even neurons, can
be stimulated electrically, chemically, or
magnetically.
 This can result in behaviors such as
giggling, head turning, or simulated vivid
recall.
 Researchers can see which neurons or
neural networks fire in conjunction with
certain mental experiences, and even
specific concepts.
Monitoring activity in the brain
Tools to read electrical, metabolic, and magnetic
activity in the brain:
EEG:
electroencephalogram
PET: positron emission
tomography
MRI: magnetic
resonance imaging
fMRI: functional MRI
EEG:
electroencephalogram
An EEG (electroencephalogram)
is a recording of the electrical
waves sweeping across the
brain’s surface.
An EEG is useful in studying
seizures and sleep.
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PET: positron emission
tomography
The PET scan allows us to see what
part of the brain is active by
tracing where a radioactive form
of glucose goes while the brain
performs a given task.
MRI: magnetic
resonance imaging
MRI (magnetic resonance imaging)
makes images from signals produced by
brain tissue after magnets align the spin
of atoms.
The arrows below show ventricular
enlargement in a schizophrenic patient
(right).
fMRI: functional MRI
Functional MRI reveals
brain activity and
function rather than
structures.
Functional MRI
compares successive
MRI images taken a
split second apart, and
shows changes in the
level of oxygen in
bloodflow in the brain.
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Areas of the brain and their functions
The brainstem
and cerebellum:
The limbic
(border) system:
The cortex (the
outer covering):
• coordinates
the body
• manages
emotions, and
connects
thought to
body
• integrates
information
The Brain:
Less Complex Brain Structures
Our tour of the brain begins with parts of the human
brain found also in simpler animals; these parts
generally deal with less complex functions:
Brainstem (Pons and Medulla)
Thalamus
Reticular Formation
Cerebellum
Limbic System
The Brainstem:
Pons and Medulla
The Base of the
Brainstem:
The Medulla
 The medulla controls the most basic functions
such as heartbeat and breathing.
 Someone with total brain damage above the
medulla could still breathe independently, but
someone with damage in this area could not.
The
Brainstem:
The Pons
The pons helps
coordinate automatic
and unconscious
movements.
The Thalamus (“Inner Chamber”)
 The thalamus is the
“sensory switchboard” or
“router.”
 All sensory messages,
except smell, are routed
through the thalamus on
the way to the cortex
(higher, outer brain).
 The thalamus also sends
messages from the cortex
to the medulla and
cerebellum.
Reticular (“Netlike”) Formation
 The reticular formation is a
nerve network in the
brainstem.
 It enables alertness,
(arousal) from coma to
wide awake (as
demonstrated in the cat
experiments).
 It also filters incoming
sensory information.
Cerebellum (“little brain”)
The cerebellum
helps coordinate
voluntary
movement such as
playing a sport.
The cerebellum has many other
functions, including enabling
nonverbal learning and memory.
The Limbic (“Border”) System
The limbic system coordinates:
 emotions such as fear and
aggression.
 basic drives such as hunger
and sex.
 the formation of episodic
memories.
The hippocampus
(“seahorse”)
 processes conscious,
episodic memories.
 works with the amygdala
to form emotionally
charged memories.
The Amygdala (“almond”)
 consists of two lima beansized neural clusters.
 helps process emotions,
especially fear and
aggression.
The Amygdala
 Electrical
stimulation of a
cat’s amygdala
provokes aggressive
reactions.
 If you move the
electrode very
slightly and cage
the cat with a
mouse, the cat will
cower in terror.
The Hypothalamus:
 lies below (“hypo”) the
thalamus.
 regulates body temperature and
ensures adequate food and
water intake (homeostasis), and
is involved in sex drive.
 directs the endocrine system via
messages to the pituitary gland.
Thalamus
The Hypothalamus as a Reward Center Riddle: Why did the rat
cross the grid?
Why did the rat want to
get to the other side?
Pushing the pedal that
stimulated the electrode
placed in the
hypothalamus was much
more rewarding than food
pellets.
Review of Brain Structures
The Cerebral Cortex
The lobes consist of:
 outer grey “bark” structure that is wrinkled in order to
create more surface area for 20+ billion neurons.
 inner white stuff—axons linking parts of the brain.
 180+ billion glial cells, which feed and protect neurons
and assist neural transmission.
300 billion synaptic
connections
The brain has
left and right
hemispheres
The Lobes of the Cerebral Cortex:
Preview
 Frontal Lobes
involved in speaking and
muscle movements and in
making plans and judgments
 Parietal Lobes
include the sensory cortex
 Occipital Lobes
include the visual areas;
they receive visual
information from the
opposite visual field
 Temporal Lobes
include the auditory
processing areas
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Functions of the Brain:
The Motor and Sensory Strips
Output: Motor
cortex (Left
hemisphere
section
controls the
body’s right
side)
Input: Sensory
cortex (Left
hemisphere
section receives
input from the
body’s right side)
 Axons
receiving motor
signals FROM
the cortex
Axons
sending
sensory
information
TO the cortex
Using our knowledge of functions:
Brain-computer interfaces
and neural prosthetics
 Here, a robotic arm is
operated through
controls embedded in
the motor strip of the
cortex.
 We may soon be able to
use computers to
translate neural inputs
into more commands
and words than simply
grabbing food.
Sensory Functions of the Cortex
 The sensory strip deals
with information from
touch stimuli.
 The occipital lobe deals
with visual information.
 Auditory information is
sent to the temporal
lobe.
The Visual Cortex
This fMRI scan
shows
increased
activity in the
visual cortex
when a person
looks at a
photograph.
Association function of the cortex
More complex animals have more cortical space
devoted to integrating/associating information
Association Areas:
Frontal Lobes
 The frontal lobes are
active in “executive
functions” such as
judgment, planning, and
inhibition of impulses.
 The frontal lobes are also
active in the use of
working memory and the
processing of new
memories.
Phineas Gage (1823-1860)
Case study: In a work accident, a
metal rod shot up through Phineas
Gage’s skull, destroying his eye and
part of his frontal lobes.
After healing, he was able to function
in many ways, but his personality
changed; he was rude, odd, irritable,
and unpredictable.
Possible explanation:
Damage to the frontal lobes could
result in loss of the ability to suppress
impulses and to modulate emotions.
Parietal Lobe Association Areas
This part of the brain has many functions in the
association areas behind the sensory strip:
 managing input from multiple senses
 performing spatial and mathematical reasoning
 monitoring the sensation of movement
Temporal Lobe Association Areas
Some abilities managed by association areas in this “by
the temples” lobe:
 recognizing specific faces
 managing sensory input related to sound, which helps
the understanding of spoken words
Whole-brain Association Activity
Whole-brain association
activity involves complex
activities which require
communication among
association areas across the
brain such as:
 memory
 language
 attention
 meditation and spirituality
 consciousness
Specialization and Integration
Five steps in reading a word aloud:
Plasticity: The Brain is Flexible
If the brain is damaged,
especially in the general
association areas of the
cortex:
 the brain does not
repair damaged
neurons, BUT it can
restore some functions
 it can form new
connections, reassign
existing networks, and
insert new neurons,
some grown from stem
cells
This 6-year-old had a
hemispherectomy to end lifethreatening seizures; her
remaining hemisphere
compensated for the damage.
Our Two
Hemispheres
Lateralization (“going to one side”)
The two hemispheres serve some different functions.
How do we know about these differences?
 Brain damage studies revealed many functions of
the left hemisphere.
 Brain scans and split brain studies show more about
the functions of the two hemispheres, and how they
coordinate with each other.
The intact but lateralized brain
Right-Left Hemisphere Differences
Left Hemisphere
Thoughts and logic
Details such as “trees”
Language: words and
definitions
Linear and literal
Calculation
Pieces and details
Right Hemisphere
Feelings and intuition
Big picture such as “forest”
Language: tone, inflection,
context
Inferences and associations
Perception
Wholes, including the self
SplitTo end severe
whole-brain
seizures, some
people have had
surgery to cut the
corpus callosum,
a band of axons
connecting the
hemispheres.
Brain Studies
Researchers have studied the
impact of this surgery on
patients’ functioning.
Separating the Hemispheres:
Factors to Keep in Mind
 Each hemisphere controls the opposite side of
the body AND is aware of the visual field on
that opposite side.
 Without the corpus callosum, the halves of
the body and the halves of the visual field do
not work together.
 Only the left half of the brain has enough
verbal ability to express its thoughts out loud.
Split visual field
Each hemisphere does
not perceive what each
EYE sees. Instead, it
perceives the half of the
view in front of you that
goes with the half of the
body that is controlled
by that hemisphere.
Divided Awareness in the Split Brain
Try to explain the following result:
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The divided brain in action
 Talent: people
are able to
follow two
instructions and
draw two
different shapes
simultaneously
 Drawback:
people can be
frustrated that
the right and left
sides do
different things
The Future of Brain Research
Can these questions be answered?
 Is every part of the mind’s functioning going to
be found someday on some brain scan?
 If so, have we found the mind, or is that still
something separate from the brain?