Transcript CHAPTER 2:

CHAPTER 2:
NEUROSCIENCE AND
BEHAVIOR
General
• Everything psychological is simultaneously
biological.
• We think, feel, and act with our bodies.
• By studying the links between biology and
psychology, biological psychologists are
gaining new clues to sleep and dreams,
depression and schizophrenia, hunger and
sex, stress and disease.
• In the 1800s, Franz Gall invented
phrenology, a popular theory that claimed
that bumps on the skull reveal our mental
abilities and our character traits.
• Although bumps on the skull reveal nothing
abut the brain’s underlying functions, Gall
was accurate in supposing that various brain
regions have particular functions.
Neural Communication
 We are composed of biological, psychological,
and social-cultural systems that interact.
 Psychologists study how these systems work
together to shape our behavior.
 At all levels, researchers examine how we take in
information; organize, interpret, and store it; and
use it.
 The information systems of humans and other
animals operate similarly.
• For example, although the human brain is
more complex than a rat’s, both follow the
same principles.
• This similarity permits researchers to study
relatively simple animals to discover how
our neural systems operate.
Figure 2.2 A motor neuron
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Copyright © 2007 by Worth Publishers
Neurons
• A neuron consists of a cell body and
branching fibers:
– The dendrite fibers receive information from
sensory receptors or other neurons
– the axon fibers pass that information along to
other neurons.
– A layer of fatty tissue, called the myelin sheath,
insulates the axons of some neurons and helps
speed their impulses.
Neuron’s Response
• A neural impulse fires when the neuron is
stimulated by pressure, heat, light, or
chemical messages from adjacent neurons.
• Received signals trigger an impulse only if
the excitatory signals minus the inhibitory
signals exceeds a minimum intensity called
the threshold.
• The neuron’s reaction is an all-or-none
response.
Neural Bases of Psychology:
The Structure of a Neuron
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
• The impulse, called the action potential, is
a brief electrical charge that travels down
the axon rather like manhole covers flipping
open.
• During the resting potential, the fluid
interior of the axon carries mostly
negatively charged atoms (ions) while the
fluid outside has mostly positively charged
atoms.
• Then, the first bit of the axon is depolarized
(its selectively permeable surface allows
positive ions in), and the electrical impulse
travels down the axon as channels open,
admitting ions with a positive charge.
• When these channels close, others open and
positive ions are pumped back out, restoring
the neuron to its polarized state.
Nerve Cell Communication
• When electrical impulses reach the axon
terminal, they stimulate the release of
chemical messengers called
neurotransmitters that cross the junction
between neurons called the synapse.
Table 2.1
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• After these molecules traverse the tiny
synaptic gap between neurons, they
combine with receptor sites on neighboring
neurons, thus passing on their excitatory or
inhibitory messages.
• The sending neuron, in a process called
reuptake, normally absorbs the excess
neurotransmitter molecules in the synaptic
gap.
• Different neurotransmitters have different
effects on behavior and emotion. For
example, the neurotransmitter acetylcholine
(ACh) plays a crucial role in learning and
memory.
• Found at every junction between a motor
neuron and skeletal muscle, ACh causes the
muscle to contract. The brain’s endorphins,
natural opiates released in response to pain
and vigorous exercise, explain the “runner’s
high” and the indifference to pain in some
injured people.
Impact of Drug Use
• When the brain is flooded with opiate drugs
such as heroin and morphine, it may stop
producing its own natural opiates, and
withdrawal of these drugs may result in
discomfort until the brain resumes
production of its natural opiates.
• Some drugs (agonists), such as some of the
opiates, mimic a natural neurotransmitter’s
effects or block its reuptake.
• Others (antagonists), such as botulin, inhibit
a particular neurotransmitter’s release or
block its effects.
• Researchers have used information about
brain neurotransmitters in their efforts to
create therapeutic drugs, such as those used
to alleviate depression and schizophrenia.
• The problem is that the blood-brain barrier
enables the brain to fence out unwanted
chemicals.
Nervous System Organization
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The Nervous System
• Neurons communicating with other neurons form
our body’s primary system, the nervous system.
• The brain and spinal cord form the central
nervous system (CNS).
• The peripheral nervous system (PNS) links the
central nervous system with the body’s sense
receptors, muscles, and glands. The axons
carrying this PNS information are bundled into the
electrical cables we know as nerves.
• Sensory neurons send information from the
body’s tissues and sensory organs inward to
the brain and spinal cord, which process the
information.
• Motor neurons carry outgoing information
from the central nervous system to the
body’s tissues.
• Interneurons in the central nervous system
communicate internally and intervene
between the sensory inputs and the motor
outputs.
The Peripheral Nervous System
• The somatic nervous system of the peripheral
nervous system enables voluntary control of our
skeletal muscles.
• The autonomic nervous system of the peripheral
nervous system is a dual self-regulating system
that influences the glands and muscles of our
internal organs.
• The sympathetic nervous system arouses;
• The parasympathetic nervous system calms.
Reflex Pathways
• Reflexes, simple, automatic responses to
stimuli, illustrate the spinal cord’s work.
• A simple reflex pathway is composed of a
single sensory neuron and a single motor
neuron, which often communicate through
an interneuron.
• For example, when our fingers touch a
candle’s flame, information from the skin
receptors travels inward via a sensory
neuron to a spinal cord interneuron, which
sends a signal outward to the arm muscles
via a motor neuron. Because this reflex
involves only the spinal cord, we jerk our
hand away before the brain creates an
experience of pain.
• Neurons in the brain cluster into work
groups called neural networks.
• The cells in each layer of a neural network
connect with various cells in the next layer.
• With experience, networks can learn, as
feedback strengthens or inhibits connections
that produce certain results.
• One network is interconnected with other
networks, which are distinguished by their
specific functions.
The Endocrine System
• The endocrine system’s glands secrete hormones,
chemical messengers produced in one tissue that
travel through the bloodstream and affect other
tissues, including the brain.
• Compared to the speed at which messages move
through the nervous system, endocrine messages
move more slowly but their effects are usually
longer-lasting.
• The endocrine system’s hormones influence
many aspects of our lives, including growth,
reproduction, metabolism, and mood,
keeping everything in balance while
responding to stress, exertion, and internal
thoughts.
• In a moment of danger, the adrenal glands
release the hormones epinephrine and
norepinephrine, which increase heart rate,
blood pressure, and blood sugar, providing
us with increased energy.
• The pituitary gland is the endocrine
system’s most influential gland. Under the
influence of the brain’s hypothalamus, the
pituitary’s secretions influence growth and
the release of hormones by other endocrine
glands.
• These may in turn influence both the brain
and behavior and thus reveal the intimate
connection of the nervous and endocrine
systems.
Studying the Brain
• The oldest method of studying the brain involved
observing the effects of brain diseases and
injuries.
• But MRI (magnetic resonance imaging) scans
now reveal brain structures, and
electroencephalogram (EEG), PET (positron
emission tomography), and fMRI (functional
MRI) recordings reveal activities in the living
brain.
• By surgically lesioning and electrically
stimulating specific brain areas, by
recording electrical activity on the brain’s
surface, and by displaying activity with
computer-aided brain scans, neuroscientists
examine the connections between brain,
mind, and behavior.
Figure 2.16 The brainstem and thalamus
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Copyright © 2007 by Worth Publishers
Components of the Brainstem
• The brainstem, the brain’s oldest and
innermost region, is responsible for
automatic survival functions.
• It includes the:
– medulla, which controls heartbeat and
breathing;
– reticular formation, which plays an important
role in controlling arousal.
• Atop the brainstem is the thalamus, the brain’s
sensory switchboard. It receives information from
all the senses except smell and sends it to the
higher brain regions that deal with seeing, hearing,
tasting, and touching.
• The cerebellum, attached to the rear of the
brainstem, coordinates movement output and
balance and helps process sensory information. It
also enables one type of nonverbal learning and
memory and helps us judge time, modulate our
emotions, and discriminate sounds and textures.
Figure 2.17 The brain’s organ of agility
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The Limbic System
• The limbic system has been linked
primarily to memory, emotions, and drives.
• For example, one of its neural centers, the
hippocampus, helps process memories.
• Another, the amygdala, influences
aggression and fear.
• A third, the hypothalamus, has been linked
to various bodily maintenance functions and
to pleasurable rewards.
• Its hormones influence the pituitary gland
and thus it provides a major link between
the nervous and endocrine systems.
Figure 2.18 The limbic system
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A Tour Through The Brain
(Continued)
• Limbic System:
interconnected
group of forebrain
structures involved
with emotions,
drives, and
memory
©John Wiley & Sons, Inc. 2007
Huffman: Psychology in Action (8e)
The Cerebral Cortex
• The cerebral cortex is a thin sheet of cells
composed of billions of nerve cells and their
countless interconnections. It is the body’s
ultimate control and information-processing
center.
• Glial cells support, nourish, and protect the
nerve cells of the cerebral cortex.
• Each lobe performs many functions and
interacts with other areas of the cortex.
Figure 2.25 The cortex and its basic subdivisions
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• The frontal lobes, just behind the forehead,
are involved in speaking, muscle
movements, and planning and making
judgments.
• The parietal lobes, at the top of head and
toward the rear, receive sensory input for
touch and body position.
• The occipital lobes, at the back of the head,
include visual areas.
• The temporal lobes, just above the ears,
include auditory areas.
Figure 2.32 Specialization and integration in language
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Figure 2.33 Brain activity when hearing, seeing, and speaking words
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Figure 2.23 Brain structures and their functions
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The Motor Cortex and The
Sensory Cortex
• The motor cortex, an arch-shaped region at the
rear of the frontal lobes, controls voluntary
muscle movements on the opposite side of the
body. Body parts requiring the most precise
control occupy the greatest amount of cortical
space. In an effort to find the source of motor
control, researchers have recorded messages from
brain areas involved in planning and intention,
leading to the testing of neural prosthetics for
paralyzed patients.
The Motor Cortex and The
Sensory Cortex
• The sensory cortex, a region at the front of
the parietal lobes, registers and processes
body sensations. The most sensitive body
parts require the largest amount of space in
the sensory cortex.
• The association areas are not involved in
primary motor or sensory functions. Rather,
they interpret, integrate, and act on
information processed by the sensory areas.
• They are involved in higher mental
functions, such as learning, remembering,
thinking, and speaking.
• Association areas are found in all four
lobes. Complex human abilities, such as
memory and language, result from the
intricate coordination of many brain areas.
Describe the five brain areas that would be
involved if you read this sentence aloud.
• Language depends on a chain of events in several
brain regions. When we read the sentence aloud,
the words
– (1) register in the visual area
– (2) are relayed to the angular gyrus which transforms
the words into an auditory code, which is
– (3) received and understood in the nearby Wernicke’s
area and
– (4) sent to Broca’s area, which
– (5) controls the motor cortex as it creates the
pronounced word.
• Depending on which link in this chain is
damaged, a different form of aphasia
occurs.
• For example, damage to the angular gyrus
leaves the person able to speak and
understand but unable to read.
• Damage to Wernicke’s area disrupts
understanding.
• Damage to Broca’s area disrupts speaking
A Tour Through The
Brain:
The Motor
Cortex and
Somatosensory
Cortex
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The Brain’s Plasticity
• Research indicates that some neural tissue can
reorganize in response to injury or damage.
• When one brain area is damaged, others may in
time take over some of its function. For example,
if you lose a finger, the sensory cortex that
received its input will begin to receive input from
the adjacent fingers, which become more
sensitive.
• New evidence reveals that adult humans can
also generate new brain cells.
• Our brains are most plastic when we are
young children. In fact, children who have
had an entire hemisphere removed still lead
normal lives.
The Split-Brain
• A split brain is one whose corpus callosum,
the wide band of axon fibers that connects
the two brain hemispheres, has been
severed.
• Experiments on split-brain patients have
refined our knowledge of each hemisphere’s
special functions.
Figure 2.35 The corpus callosum
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Copyright © 2007 by Worth Publishers
• In the laboratory, investigators ask a splitbrain patient to look at a designated spot,
then send information to either the left or
right hemisphere (by flashing it to the right
or left visual field).
• Quizzing each hemisphere separately, the
researchers have confirmed that for most
people the left hemisphere is the more
verbal and the right hemisphere excels in
visual perception and the recognition of
emotion.
• Studies of people with intact brains have
confirmed that the right and left
hemispheres each make unique
contributions to the integrated functioning
of the brain.
• On occasion, hemispheric specialization,
called lateralization, has been shown to
occur.
Brain Organization, Handedness, and Mortality.
• About 10 percent of us are left-handed.
• Almost all right-handers process speech primarily
in the left hemisphere.
• Left-handers are more diverse.
• More than half process speech in the left
hemisphere, about a quarter in the right, and the
last quarter use both hemispheres equally.
• The finding that the percentage of left-handers
declines dramatically with age led researchers to
examine the leftie’s health risks.
• Left-handers are more likely to have
experienced birth stress, such as prematurity
or the need for assisted respiration.
• They also endure more headaches, have
more accidents, use more tobacco and
alcohol, and suffer more immune system
problems.
• However, researchers continue to debate
whether left-handers have a lower life
expectancy.
A Tour Through The Brain:
Lateralization
• The left and right
hemispheres of the
brain each specialize
in particular operations.
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Our Genetic Inheritance
• To answer questions about the influence of
nature versus nurture, psychologists use
behavioral genetics research.
• Behavioral Genetics: studies the relative
effects of nature (heredity, genes, and
chromosomes) and nurture
(environment) on
behavior and
mental
processes.
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Our Genetic Inheritance: Genes &
DNA
• The nucleus of every cell
in our body contains
genes, which carry the
code for hereditary
transmission. These genes
are arranged along
chromosomes (strands of
paired DNA).
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Our Genetic Inheritance: Twin
Research
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Our Genetic Inheritance

Evolutionary Psychology:
studies how natural selection
and adaptation help explain
behavior and mental processes
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Our Genetic Inheritance:
Better Living Through
Neuroscience
• Neuroplasticity: brain’s lifelong ability to
reorganize and change its structure
and
function
• Neurogenesis: the division and differentiation
of non-neuronal cells to produce neurons
• Stem cells: Precursor (immature) cells that give
birth to new specialized cells
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Chromosome, DNA, Gene, &
Genome
• Every cell nucleus contains the genetic master
code for the body.
• Within each cell are 46 chromosomes with 23
donated by each parent.
• Each chromosome is composed of a coiled chain
of a molecule, called DNA (deoxyribonucleic
acid).
• Genes are DNA segments that, when “turned on,”
form templates for the production of proteins.
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Figure 3.1 The genes: Their location and composition
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Chromosome, DNA, Gene, &
Genome
• We inherit one set of 23 chromosomes from each
parent.
• The two sets form pairs that contain alternate
genes for the same traits.
• Sometimes, one gene is dominant and “overrides”
the recessive gene. For example, in the
determination of eye color, the brown-eye gene is
dominant.
• Genome: complete set of genetic material
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• By directing the manufacture of proteins, the
approximately 30,000 genes that compose the human
body determine our individual biological
development.
• The genome provides the complete instructions for
making an organism, consisting of all the genetic
material in the organism’s chromosomes.
• Variations at particular gene sites in the DNA define
each person’s uniqueness.
• Human traits are influenced by gene complexes, that
is, by many genes acting in concert.
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Genes & Twins
• Comparisons of identical twins, who are genetic
clones, and fraternal twins, who develop from
separate eggs, help behavior geneticists tease apart
the effects of heredity and environment.
• Research findings show that identical twins are
much more similar than fraternals in abilities,
personality traits, and even interests.
• Genes matter!!!!
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• The discovery that identical twins separated at
birth show remarkable similarities also
suggests genetic influence.
• Indeed, separated fraternal twins do not
exhibit similarities comparable to those of
separated identical twins. Genes also influence
the social effects of such traits.
• Identical twins are more likely to both share
similar risk for developing Alzheimer’s and of
experiencing divorce
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Figure 3.2 Same fertilized egg, same genes; different eggs, different genes
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Adoption Studies
• Adoption studies enable comparisons with both
genetic and environmental relatives.
• Adoptees’ traits & personality bear more similarities
to their biological parents than to their caregiving
adoptive parents.
• Nonetheless, the latter do influence their children’s
attitudes, values, manners, faith, and politics.
• Clearly nature and nurture shape one’s
developing personality.
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Adoption Studies
• Adoptive parents are least likely to influence
personality traits.
• They are more likely to influence attitudes,
moral values, religious values, etc.
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Temperament Stability
• An infant’s temperament includes inborn
emotional excitability.
• From the first weeks of life, some babies are more
relaxed and cheerful, while others are more tense
and irritable.
• These differences in temperament tend to endure.
For example, the most emotionally intense
preschoolers tend to be relatively intense as young
adults.
• Compared with fraternal twins, identical twins
have more similar temperaments.
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Heritability
• Using twin and adoption methods, behavior
geneticists can mathematically estimate the
heritability of any trait—the extent to which
variation among individuals is due to their
differing genes.
• If the heritability of intelligence is 50 percent, this
does not mean that one’s intelligence is 50 percent
genetic.
• Instead it means that we can attribute to genetic
influence 50 percent of the observed variation
among people.
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• The heritability of a specific trait may vary,
depending on the range of populations and
environments studied.
• As environments become more similar,
heredity as a source of differences becomes
more important.
• Our genes affect how our environment reacts
to and influences us.
• Nature enables nurture.
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• Heritable individual differences need not
imply heritable group differences.
• Genes and environment work together.
Because of human adaptability, most
psychologically interesting traits are expressed
in particular environments.
• In other words, genes are self-regulating; they
can react differently in different environments.
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Genetically Influenced Trait
• We are all the products of interactions between
our genetic predispositions and our surrounding
environments.
• A baby who is genetically predisposed to be social
and easygoing may, in contrast to one who is less
so, attract more affectionate and stimulating care
and thus develop into a warmer and more outgoing
person.
• Similarly, a stressful environment can trigger
genes that affect the production of
neurotransmitters that underlie depression.
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Genetically Influenced Trait
• Genes respond to environments
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Genetically Influenced Trait
• There is now a large body of evidence that
supports the conclusion that individual differences
in most, if not all, reliably measured psychological
traits, normal and abnormal, are substantially
influenced by genetic factors.”
• Big Five (extraversion, agreeableness,
conscientiousness, neuroticism, and openness) and
the Big Three (positive emotionality, negative
emotionality, and constraint), is in the range of 40
to 50 percent
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Genetically Influenced Trait
• Shared environmental factors are the
dominant influence on IQ
• Psychological Interests = .36
• Psychiatric Illnesses:
•
•
•
•
•
Schizophrenia = .80
Depression = .40
Anxiety Disorders = .20 to .40
Alcoholism = .50 to .60
Antisocial Personality Disorder = .41 to .46
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Genetically Influenced Trait
• Does childhood maltreatment may produce an
antisocial adult?
• those with high-active monoamine oxidase A (MOA)
genes are virtually immune to the effects of
maltreatment
• Those with low-active genes are much more antisocial
if maltreated, yet slightly less antisocial if not
maltreated.
• In short, maltreatment alone does not produce antisocial
behavior; the low-active gene must also be present.
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