5th Edition
Psychology
Stephen F. Davis
Emporia State University
Joseph J. Palladino
University of Southern Indiana
PowerPoint Presentation by
Cynthia K. Shinabarger Reed
Tarrant County College
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Copyright © Prentice Hall 2007
2-1
Chapter 2
5th Edition
Behavioral
Neuroscience
Copyright © Prentice Hall 2007
2-2
Biology and Behavior
• In their efforts to understand the brain and
the rest of the nervous system, many
researchers have adopted an
evolutionary perspective which focuses
on the role a particular physical structure
or behavior plays in helping an organism
adapt to its environment over time.
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Charles Darwin
• 1859: The Origin of Species: By means of
Natural selection or the preservation of
favoured races in the struggle for life.
• As Miami University approaches our 200th
year in “2009” others will be celebrating
the 150th anniversary of Darwin’s
important book, The Origin of Species.
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5 BASIC PRINCIPLES OF
DARWINIAN EVOLUTION THEORY
[FROM: MICHAEL SHERMER’S (2002) In Darwin’s Shadow: The life and Science
of Alfred Russel Wallace. New York, NY: Oxford University Press, p. 207.]
•
•
•
•
•
EVOLUTION: CHANGE (in behavior)THROUGH TIME.
DESCENT WITH MODIFICATION: THE MODE OF
EVOLUTION BY BRANCHING COMMON DESCENT.
GRADUALISM: CHANGE (in behavior) IS SLOW,
STEADY, STATELY. NATURA NON FACIT SALTUS.
GIVEN ENOUGH TIME EVOLUTION CAN ACCOUNT
FOR THE ORIGIN OF NEW SPECIES.
MULTIPLICATION OF SPECIATION: EVOLUTION
PRODUCES NOT JUST NEW SPECIES (behavior), BUT
AN INCREASING NUMBER OF NEW SPECIES
(behaviors).
NATURAL SELECTION: THE MECHANISM OF
EVOLUTIONARY CHANGE CAN BE SUBDIVIDED INTO
FIVE STEPS: (SEE NEXT TWO SLIDES).
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Biology and Behavior
• Darwin maintained that evolution unfolds
according to the principle of natural
selection: the process by which inherited
characteristics that lead to an advantage
in adapting to the environment are more
likely to be passed on (through genetic
material) to future generations.
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FIVE STEPS OF
NATURAL SELECTION
• 1. POPULATIONS [behaviors] TEND TO INCREASE INDEFINITELY
IN A GEOMETRIC RATIO. [FROM OBSERVATION]
• 2. IN A NATURAL ENVIRONMENT, HOWEVER, POPULATION
[behavior] NUMBERS STABILIZE AT A CERTAIN LEVEL. [FROM
OBSERVATION]
• 3. THERE MUST BE A “STRUGGLE FOR EXISTENCE” SINCE NOT
ALL ORGANISMS [behaviors] PRODUCED CAN SURVIVE. [FROM
INFERENCE]
• 4. THERE IS VARIATION IN EVERY SPECIES [behaviors]. [FROM
OBSERVATION]
• 5. IN THE STRUGGLE FOR EXISTENCE, THOSE VARIATIONS THAT
ARE BETTER ADAPTED TO THE ENVIRONMENT LEAVE BEHIND
MORE OFFSPRING THAN THE LESS WELL ADAPTED
INDIVIDUALS, ALSO KNOWN AS DIFFERENTIAL REPRODUCTIVE
SUCCESS. [FROM INFERENCE]
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Biology and Behavior
• In addition to studying the process of
natural selection, researchers focus on
discovering the actual genetic material
responsible for the physical structure or
behavior under investigation.
• The researchers who study the biological
basis of animal and human behavior are
working in an area called behavioral
neuroscience.
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2-8
Biology and Behavior
• This relatively new term focuses attention
on the relation between biological factors
and behavior.
• The term implies that these scientists
represent several disciplines including
psychology (especially physiological
psychologists), biology, medicine, and
others.
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Biology and Behavior
• To survive, human beings must be able to
perform three interrelated activities:
sensing events, or stimuli; processing
stimuli; and responding to stimuli.
• A stimulus is a feature in the
environment—such as a traffic light, a
sign, an alarm, or the smell of smoke—
that may provoke a response.
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Biology and Behavior:
THE VAKTC MODEL
• V: Visual
– Eyes “light”
• A: Auditory
– Ears “sound”
• K: Kinesthetic
– Whole body in motion
• T: Tactile
– Touch/Skin “feeling”
• C: Chemio-Receptive
– Smell and Taste
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Levitin, Daniel J. (2006). This is your brain on music: The
science of a human obsession. New York: Dutton.
Levitin is a “neuroscientist” with an
evolutionary psychology theoretical
perspective. This book describes the
evolutionary origins of music.
Levitin’s home page is:
http://www.psych.mcgill.ca/faculty/levitin.html
His other home page is:
http://www.psych.mcgill.ca/levitin/
Copyright © Prentice Hall 2007
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Biology and Behavior
• Receptors are specialized cells of the
nervous system that sense stimuli.
• The second activity in the chain is
interpreting, or processing, the information
that reaches the receptors.
• This processing typically takes place in the
brain.
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Biology and Behavior
• Once we’ve processed and understood
the sensory input, we may need to
respond to it.
• Therefore, the third activity occurs when
the brain sends messages to the muscles
to produce a response.
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The Nervous System
• The activities of sensing, processing, and
responding are coordinated and controlled
by the nervous system, which has two
major divisions: the central nervous
system (CNS) and the peripheral
nervous system (PNS).
• The CNS consists of the brain and spinal
cord; the PNS connects the outer (or
periphery) portions of the body with the
CNS.
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The Nervous System
• The PNS consists of all the parts of
the nervous system that are outside
the CNS.
• The two major divisions of the PNS
are the somatic nervous system and
the autonomic nervous system.
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Divisions of the Nervous System
• Central Nervous
System
– Brain
– Spinal cord
• Peripheral Nervous
System
– Somatic
– Autonomic
• Sympathetic
• Parasympathetic
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The Nervous System
• The somatic nervous system of the PNS
makes contact with the environment.
• It consists of nerves that connect
receptors to the spinal cord and brain, as
well as nerves that go to and from the
brain and spinal cord to the muscles.
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The Nervous System
• Nerves that carry information from receptors to
the brain and spinal cord are called afferent
(sensory) nerves.
• Nerves that carry information from the brain
and spinal cord to the muscles are called
efferent (motor) nerves.
• Because the responses we make are often
planned and organized, the somatic division is
said to be a voluntary system—that is, under
our conscious control.
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The Nervous System
• The autonomic nervous system of the PNS
affects our organs and glands in ways that
regulate bodily functioning.
• Because the autonomic nervous system
operates without our conscious awareness, it is
described as an automatic, or involuntary,
system.
• The autonomic nervous system has two main
components: the sympathetic nervous system
and the parasympathetic nervous system.
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The Nervous System
• The sympathetic nervous system mobilizes
the body in times of stress or danger.
• The parasympathetic nervous system slows
the processes that have been accelerated by
activation of the sympathetic nervous system.
• These effects return the body to a more normal
or balanced state of functioning characterized by
an optimal range of physiological processes
called homeostasis.
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The Nervous System
• The spinal cord serves as the body’s
information superhighway.
• Information that is not processed solely
within the spinal cord itself is sent to the
brain via ascending pathways; information
that is sent back down from the brain
follows descending pathways.
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The Nervous System
• Within the CNS, interneurons connect
neurons to each other.
• When information provided by the sensory
nerves does not have to travel all the way
to the brain to produce a response,
automatic behaviors known as reflexes
are produced.
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The Endocrine System
• Endocrine system:
– Ductless glands that
regulate growth,
reproduction,
metabolism, mood,
and some behavior
• Hormones:
– Chemical messengers
secreted into the
bloodstream
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The Endocrine System
• The endocrine system consists of glands that
produce and secrete (release) chemicals
known as hormones.
• When stimulated, endocrine glands secrete
hormones into the bloodstream.
• The pineal gland, located deep in the center
of the brain, produces the hormone melatonin,
especially at night.
• This hormone is important in regulating our
sleep–wake cycle.
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The Endocrine System
• Located near the stomach and small
intestine, the pancreas secretes one of
the best-known hormones, insulin.
• The cells of our body require insulin to use
blood sugar (called glucose); without
insulin, cells do not receive adequate
nourishment from the available glucose.
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The Endocrine System
• The hypothalamus is both an endocrine
gland and a key center for a wide variety
of behaviors related to survival.
• The hypothalamus signals its close
neighbor, the pituitary, to release
hormones that have a range of effects.
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The Endocrine System
• The pituitary gland is often called the
master gland because its secretions
control many other glands.
• The pituitary is responsible for release of
somatotropin, a growth hormone that acts
directly on bones and muscles to produce
the growth spurt that accompanies
puberty.
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2-28
The Endocrine System
• The thyroid gland secretes thyroxine, which
regulates the body’s growth and metabolic rate.
• The gonads—ovaries in women and testes in
men—produce sex hormones (androgens in
men; estrogens in women) that activate
reproductive organs and structures at puberty.
• These hormones also affect the appearance of
secondary sex characteristics like facial and
body hair, change of voice, and breast
development.
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The Endocrine System
• When you experience stress, the adrenal
glands secrete epinephrine and
norepinephrine (originally called
adrenaline and noradrenaline,
respectively), which power sympathetic
nervous system activity.
• These hormones help us respond to stress
by producing the fight-or-flight response.
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Neurons: Basic Cells of the
Nervous System
• The cells that make up the nervous
system are called neurons.
• Neurons are composed of:
– dendrites that receive signals from
adjacent neurons,
– a cell body or soma,
– an axon that transmits signals, and
– terminal buttons that contain
neurotransmitters.
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Structure of a Neuron
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Neurons: Basic Cells of the
Nervous System
• One of the major differences among
neurons is found in their axons.
• Some axons are surrounded by a myelin
sheath, which is a fatty protein substance.
• Myelin is whitish in appearance, which
accounts for the whitish appearance of the
spinal cord with its long myelin-covered
axons.
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Neurons: Basic Cells of the
Nervous System
• The myelin sheath serves as a kind of
living electrical tape that insulates the
axons, thus preventing short circuits
between neurons.
• In addition, it allows the signal to move
along the axon faster.
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Neurons: Basic Cells of the
Nervous System
• Myelin does not cover the entire length of
any axon; it is interrupted by what are
called nodes of Ranvier.
• A nerve impulse “jumps” successively from
one node of Ranvier to the next, resulting
in transmission that is up to 100 times
faster than neural impulses on
unmeylinated axons.
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Neurons: Basic Cells of the
Nervous System
• The myelin sheath is composed of glial
cells (from the Greek word for “glue”),
another special type of cell found in the
nervous system.
• Glial cells have several functions:
removing waste, occupying vacant space
when neurons die, guiding the migration of
neurons during brain development, and
insulation.
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Neurons: Basic Cells of the
Nervous System
• Because a neural signal is sent from one neuron
to the next through the terminal buttons of the
axons, the most common arrangement is for a
neuron’s terminal buttons to be near, but not
touching, the receptive dendrites of neighboring
neurons.
• The membrane on the side that sends the
message is the presynaptic membrane and the
membrane on the receiving side of the synapse
is the postsynaptic membrane.
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Neurons: Basic Cells of the
Nervous System
• The most common arrangement at the end
of an axon consists of a terminal button to
send the signal, a dendrite to receive the
signal, and the gap between the two,
which is the synapse.
• Neurotransmitters are special chemicals
stored in vesicles of the terminal buttons at
the ends of axons.
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The Synapse
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Neurons: Basic Cells of the
Nervous System
• When the electrical signal reaches the
terminal buttons, it causes the vesicles in
the terminal button to release a chemical
signal in the form of a neurotransmitter
into the synapse.
• As the neurotransmitter enters the
synapse, it contacts the postsynaptic
membrane (usually the dendrite) of the
next neuron.
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Neurons: Basic Cells of the
Nervous System
• The neuron that is receiving the
neurotransmitter may become more likely
to transmit the message to subsequent
neurons; this process is called excitation.
• In other instances, the neuron that
receives the neurotransmitter becomes
less likely to transmit the message to
subsequent neurons; this process is called
inhibition.
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2-41
Neurons: Basic Cells of the
Nervous System
• Dopamine is a neurotransmitter that controls
arousal levels and plays a significant role in
motor movement.
• Dopamine also is involved in brain pathways
that are responsible for reward and
punishment.
• Serotonin plays a role in weight regulation,
sleep, depression, suicide, obsessive–
compulsive disorder, aggression, and a wide
range of other disorders and behavior
problems.
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Neurons: Basic Cells of the
Nervous System
• Acetylcholine controls activity in brain areas
related to attention, learning, and memory.
• Glutamate is called upon quite frequently to
keep the lines of communication among
neurons open, engage in passing along
information, and may well play a role in
learning.
• Excessive levels of glutamate may cause
neurons to become overexcited, and they may
die as a consequence.
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Neurons: Basic Cells of the
Nervous System
• GABA (gamma-aminobutyric acid) is an
inhibitory neurotransmitter that is widely
distributed throughout the brain and the
spinal cord.
• The damping effect of inhibitory
neurotransmitters is necessary to create a
balance in the brain.
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Neurons: Basic Cells of the
Nervous System
• Norepinephrine (which is also a
hormone) induces physical and mental
arousal and heightens our mood.
• It is found in the autonomic nervous
system and is part of the power behind the
fight-or-flight response.
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Neurons: Basic Cells of the
Nervous System
• Synapses must be cleared, and cleared
rapidly, before additional signals can be
transmitted.
• The synapse is cleared in one of two
ways, depending on the particular
neurotransmitter involved.
• In the first method, breakdown, the
neurotransmitter is broken down and
removed from the synapse.
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Neurons: Basic Cells of the
Nervous System
• After the neurotransmitter affects the next
neuron, an enzyme breaks it down.
• The second method for clearing the
synapse, reuptake, involves taking the
neurotransmitter back into the vesicles of
the terminal buttons from which it came.
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Neurons: Basic Cells of the
Nervous System
• Most drugs exert their effects by influencing
the operation of a neurotransmitter: some
drugs increase the effectiveness of
neurotransmitters; other drugs reduce their
effectiveness.
• Drugs that promote or enhance the operation
of a neurotransmitter are called agonists.
• Drugs that oppose or inhibit the operation of
a neurotransmitter are called antagonists.
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Agonists
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Antagonists
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Neurons: Basic Cells of the
Nervous System
• Neuromodulators can influence the
transmission of signals between neurons.
• The release and action of
neurotransmitters are confined to
synapses in a specific area; the
distribution of neuromodulators is more
widespread.
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Neurons: Basic Cells of the
Nervous System
• For example, neuromodulators can have
simultaneous effects on diverse brain regions;
their activity may be indirect and longer-lasting.
• Some neuromodulators produce their effects
by facilitating the release of neurotransmitters;
others inhibit the release of neurotransmitters.
• One of the best-known neuromodulators,
morphine, relieves pain.
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Neurons: Basic Cells of the
Nervous System
• If you examine the chemicals on the
outside of the neuron’s semipermeable
cell membrane and compare them with the
chemicals on the inside of the cell
membrane, you will notice a difference in
small electrically charged particles called
ions.
• The two types of ions, positive (+) and
negative (-), resemble the two poles or
ends of a battery.
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Neurons: Basic Cells of the
Nervous System
• When a neuron is not sending or receiving
a signal, it is in a resting state, with more
negative ions on the inside than on the
outside.
• Relative to the outside, the inside of the
neuron is about 270 millivolts (a millivolt,
mV, is 1/1,000th of a volt) when the neuron
is in the resting state.
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Neurons: Basic Cells of the
Nervous System
• Because of this unequal distribution of
ions, the neuron is polarized, like a battery.
• This 270-mV difference in electric charge
between the inside and outside of a
neuron at rest is the resting potential.
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Neurons: Basic Cells of the
Nervous System
• When a neurotransmitter enters the
synapse it may result either in
– depolarization (the neuron becomes
less negatively charged) or,
– hyperpolarization (the neuron
becomes more negatively charged).
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Neurons: Basic Cells of the
Nervous System
• When excitatory neurotransmitters occupy
appropriate receptor sites, they cause the
cell membrane to allow positive ions to
pass inside.
• The increase of positive ions on the inside
of the neuron causes the resting potential
to drop.
• This change, which brings the potential
closer to zero, is depolarization.
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Neurons: Basic Cells of the
Nervous System
• If enough of the neurotransmitter is
present to cause the dendrite and soma to
depolarize to between 265 and 260 mV,
the neuron generates its own electrical
signal.
• At this threshold (the minimum amount of
change required for the neuronal response
to occur) the axon membrane suddenly
allows large quantities of positive ions to
rush inside.
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Neurons: Basic Cells of the
Nervous System
• In less than a millisecond the neuron
changes from 260 to 130 mV, completely
reversing its electrical nature or polarity.
• This reversal along the axon is the neural
signal and is called an action potential, or
all-or-none response.
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Neurons: Basic Cells of the
Nervous System
• Once the dendrite and soma reach the
threshold, the action potential spreads
rapidly down the axon until it reaches the
terminal buttons, where it causes the
release of a neurotransmitter.
• At the same time that the action potential
is being transmitted, the initiating
neurotransmitter is being cleared out of
the synapse.
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How Neurons Communicate
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Neurons: Basic Cells of the
Nervous System
• Removal of the neurotransmitter causes
the receiving neuron to return to a resting
state and allows it to generate another
action potential—that is, to fire again.
• When the neuron is being reset—called
the refractory period—the neuron cannot
fire again.
• The action potential and the refractory
period occur within 2 milliseconds.
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Neurons: Basic Cells of the
Nervous System
• Not all neurons respond to the presence of a
neurotransmitter by depolarizing or generating
an action potential; the result may be just the
opposite.
• In these cases the neurotransmitter is inhibitory,
and causes additional negative ions to cross the
cell membrane and enter the neuron.
• When inhibition occurs, the neuron becomes
more negative than it was during the resting
state (hyperpolarized), making an action
potential harder, if not impossible, to generate.
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The Brain: A Closer Look
• In the 1800s a German physician and anatomist
Franz Joseph Gall developed the
pseudoscience phrenology (“science of the
mind”).
• Gall believed that various skills and personality
characteristics (which he called mental
“faculties”) could be located on the brain.
• This early attempt to understand the brain
contained an element of truth as Gall believed
that skills and characteristics could be localized
in certain areas of the brain.
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The Brain: A Closer Look
• In 1861, the French physician Paul Broca
used a technique for understanding the
brain—the clinical or case study method.
• Broca discovered an area on the left
hemisphere of the brain that is responsible
for the ability to produce speech.
• In recognition of his discovery, this speech
area is called Broca’s area.
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The Brain: A Closer Look
• Phineas Gage’s story is one of the most
famous cases of survival from massive
brain injury.
• Gage, a railroad foreman, was working
with explosives in Cavendish, Vermont, on
September 13, 1848, trying to clear a
railroad right-of-way through granite
bedrock.
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The Brain: A Closer Look
• Gage’s attention was distracted from the
task at hand and a tamping iron became a
13¼ -pound, 3-foot 7-inch rocket that shot
through the left side of Gage’s face and
exited through his head.
• Before the accident, Gage had been an
excellent worker who got along well with
others and carried through with his plans.
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The Brain: A Closer Look
• After the accident, he made plans he
never carried out, used gross profanity,
refused to listen if what others said
interfered with what he wanted, and was
very moody.
• The study of people who have suffered
brain damage like Phineas Gage provides
abundant information about brain
functioning.
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The Brain: A Closer Look
• In 1904, brain researchers created a device that
made studying certain brain structures possible.
• Before the invention of this device, structures
that were deep in the brain could be examined
only by removing or damaging the tissue that
covered them.
• The stereotaxic instrument holds the head in a
fixed position and allows an electrode (a fine
piece of specially treated wire) to be inserted
into a specified area of a patient’s brain.
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The Brain: A Closer Look
• The electrode is thin enough that it does
not damage tissue as it passes through.
• The electrode can record electrical brain
activity, stimulate brain activity with a mild
electric current, or destroy a brain area by
passing a strong electric current through it.
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The Brain: A Closer Look
• More recently developed techniques have
enabled neuroscientists to examine brain
functions and anatomy without resorting to
autopsy or invasive stereotaxic surgery.
• In 1929 Hans Berger developed the
electroencephalograph (EEG), a device
that monitors and records the brain’s
electrical activity.
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The Brain: A Closer Look
• Brain waves (identified by Greek letters)
are distinguished by their frequency, which
is measured in cycles per second (called
hertz and abbreviated Hz), and their
amplitude (the height of the wave on the
EEG record), which reflects strength.
• Brain researchers have labeled a number
of different types of brain waves; each is
generally associated with a particular state
of consciousness.
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The Brain: A Closer Look
• Alpha waves are fast brain waves (8 to 12
Hz) that are not high in amplitude.
• The brain generally produces alpha waves
when the individual is in a calm, relaxed
state and is not concentrating on anything
in particular.
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The Brain: A Closer Look
• Beta waves are very fast brain waves (13
to 30 Hz), but are not high in amplitude.
• They are associated with mental activity
such as reading, taking notes in class, or
answering test questions.
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The Brain: A Closer Look
• Theta waves are slow brain waves (3.5 to
7 Hz) that are irregular in frequency and
low in amplitude.
• When we are in a light stage of sleep or
daydreaming, our brains are likely to
produce this type of wave; however, theta
waves are normal in waking children up to
13 years of age.
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The Brain: A Closer Look
• Delta waves are the slowest brain waves
(below 3.5 Hz) and the highest in
amplitude.
• Delta waves are quite common in infants
up to 1 year of age and in the deepest
stages of sleep.
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The Brain: A Closer Look
• The advent of computers has led to major
advances in the study of the brain.
• Positron emission tomography (PET) is
an imaging technique that involves
monitoring the metabolic activity of the
brain.
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The Brain: A Closer Look
• Computerized axial tomography (CT or
CAT) involves the production of a large
number of x-rays interpreted by a
computer.
• Magnetic resonance imaging (MRI)
involves the use of radio waves and a
strong magnetic field to produce a signal
that can be interpreted by a computer.
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The Brain: A Closer Look
• Functional magnetic resonance
imaging (fMRI) is a modification of the
standard MRI procedure that allows both
structural and temporal images of the
brain to be gathered.
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The Brain
• The brain is divided
into the hindbrain, the
midbrain, and the
forebrain.
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The Brain
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The Brain: A Closer Look
• The major components of the hindbrain
are the medulla, the pons, and the
cerebellum.
• From an evolutionary perspective, these
are the oldest parts of the brain, and they
have important survival functions.
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The Brain: A Closer Look
• The medulla (short for medulla oblongata)
contains our respiratory center, which
keeps us breathing, especially when we
are asleep.
• The medulla also controls heart rate,
vomiting, swallowing, yawning, and blood
circulation.
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The Brain: A Closer Look
• The pons connects the two halves of the
brain at the hindbrain level; this part of the
hindbrain is important for sleep and
arousal.
• The cerebellum coordinates skilled
movement sequences that deal with
objects in motion.
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The Brain: A Closer Look
• Together the hindbrain and midbrain are known
as the brain stem because they form the stem,
or stalk, on which the remainder of the brain
rests.
• The midbrain also is composed of nerve
pathways that go to and from higher brain
centers.
• Psychologists have found that this complex
network of fibers, known as the reticular
formation, is very important in controlling our
level of arousal or alertness.
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The Brain: A Closer Look
• The forebrain is a part of the brain that is
divided into two distinct halves with
duplicate structures in each half.
• These two halves or hemispheres are
connected by a wide band of fibers known
as the corpus callosum (“hard body”).
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The Brain: A Closer Look
• The two hemispheres of the forebrain
communicate with each other through the
corpus callosum.
• The cerebral cortex (cerebrum) is the
convoluted (wrinkled) outer layer of the
brain.
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The Brain: A Closer Look
• Deep down in the brain—below the
cortex—is the basal ganglia, a series of
interconnected structures that play a
significant role in motor movement.
• The limbic system is a group of
interrelated subcortical structures that are
involved in the regulation of emotions and
motivated behaviors such as hunger,
thirst, aggression, and sexual behavior.
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Major Components of the Limbic
System
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The Brain: A Closer Look
• The thalamus sends sensory information
to the cerebral cortex and other parts of
the brain.
• Each cerebral hemisphere has four
specific areas, called lobes—the frontal,
temporal, parietal, and occipital lobes.
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The Brain: A Closer Look
• The frontal lobes are responsible for
language, movement, reasoning, planning,
problem-solving, and personality.
• The major responsibility of the parietal
lobes is to process every sensation
except smell.
• The parietal lobes can also be thought of
as a sensory integrator because they are
responsible for body position as well as
our sensory cortex or somatosensory strip.
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The Brain: A Closer Look
• The temporal lobes have several
functions, including the processing of
auditory information; in most people the
left side interprets the meaning of speech
(Wernicke’s area).
• These lobes also play a significant role in
learning, memory, and emotions.
• The occipital lobes’ primary responsibility
is to processes visual information.
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The Brain: A Closer Look
• Neuroscientists have focused on the brain
structures responsible for language as well
as the problems that develop when these
areas are damaged.
• Broca’s area (in most people it is located
in the left frontal lobe) is the key area
involved in language production.
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The Brain: A Closer Look
• Wernicke’s area (in most people it is
located in the left temporal lobe) is the key
area involved in understanding language.
• Damage to either or both areas can have
significant effects on a person’s language
abilities.
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The Brain: A Closer Look
• The term aphasia refers to a loss of the
ability to speak or understand written or
spoken language.
• Damage to Broca’s area results in
nonfluent aphasia.
• People with this type of aphasia have
difficulty producing speech, although they
generally understand what others say to
them.
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The Brain: A Closer Look
• In 1874, the German neurologist Carl
Wernicke (1848–1905) identified a second
brain area that plays a significant role in
language.
• Damage to Wernicke’s area results in
language problems called fluent aphasia.
• In contrast to the speech of people with
damage to Broca’s area, damage to
Wernicke’s area results in fluent-sounding,
but meaningless speech.
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The Brain: A Closer Look
• Broca’s and Wernicke’s aphasias are the
two most common, but there are other
types.
• For example, optic aphasia is the inability
to read more than one letter at a time,
whereas a person suffering from word
deafness cannot understand spoken
language despite the presence of normal
hearing and reading abilities.
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The Brain: A Closer Look
• Apraxias are deficits in nonverbal skills.
• Apraxias involve damage to the right
hemisphere.
• Depending on the site of the damage, one
might observe a dressing apraxia, in which
a person has trouble putting clothing on
one side of the body, or a constructional
apraxia, in which a person cannot copy a
simple drawing.
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The Brain: A Closer Look
• In addition to apraxias, the right
hemisphere controls prosody, the ability
to express emotion.
• People suffering from motor aprosodia
speak in a flat monotone regardless of
their real feelings.
• Such people simply cannot display
emotions.
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The Brain: A Closer Look
• In the early 1960s, two neurosurgeons,
Philip Vogel and Joseph Bogen,
discovered that cutting the corpus
callosum reduced seizures in untreatable
epileptic patients.
• Even though we do not know exactly why
this operation controls seizures, it is still
performed as a last resort in severe cases
of epilepsy.
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The Brain: A Closer Look
• Research by Nobel Prize winner Roger
Sperry and his colleague Michael
Gazzaniga showed that in people with a
severed corpus callosum, the two
hemispheres appeared to be doing
different things.
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The Brain: A Closer Look
• Studies of split brain patients support the
conclusion that the left hemisphere is
involved in speech and language production.
• Although the right hemisphere has limited
language functions, it is essential for adding
emotional content to our speech.
• It is also important for spatial abilities such as
recognizing complex geometric patterns.
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The Brain: A Closer Look
• Plastic can be molded and changed into
many forms.
• It is a pliable material that can take on
different forms and even functions.
• In some ways, the same can be said of the
brain, which can change remarkably over
time.
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The Brain: A Closer Look
• One reason the brain, especially in
children, can change in response to
experiences (including removal of an
entire hemisphere) is that humans do not
come into this world with a fully developed,
hard-wired brain.
• New data indicates that it is possible for
new neurons to develop in the human
brain (neurogenesis).
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