Transcript Document

The Brain
Carolyn R. Fallahi, Ph. D.
7/18/2015
Dr. Carolyn R. Fallahi
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Phrenology
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The idea that specific
mental processes are
located in, or
associated with,
discrete parts of the
brain can be traced
back to the early 1800s
when a German
physician, Franz Gall,
invented phrenology.
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Phrenology
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Phrenology was the study of the bumps on
the skull which could reveal our mental
abilities and character traits.
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Phrenology
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Neurons and neural impulses
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A Neuron is defined as an individual nerve cell in the
nervous system. The neuron is the simplest element
of the nervous system.
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The Cell body
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A neuron is made up of the following:
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Cell body – central part of the nerve cell. Contains the
cell’s control center.
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The Nucleus
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Nucleus – helps feed the neuron and keep it alive (the
cell’s control center).
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Dendrites
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Dendrites – small branches off the cell body which
receive messages from other neurons.
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Axons
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Axons are small branches at the other end of the
neuron that carries messages away from the axon
and transmits those messages to the next neuron.
Axon tracts stretch-grown
to 5 cm. Axon tracts
(middle) bridge two
populations of neurons
(top and bottom).
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Axon Terminals
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Synapse
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Neural Transmission
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When the neuron is stimulated, it generates an
impulse that travels down the axon and into
the axon terminals where it causes the release
of specialized chemicals.
These chemicals are called neurotransmitters.
They travel a small distance across a synapse
to the next neuron.
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Neural Transmission
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Neurons are long sacs filled with fluid on the
inside and bathed in fluid on the outside.
The liquid on the inside consists of chemicals
with either a positive or negative charge ===
this called ions.
If inside the cell is more negatively charged,
then the overall cell is negative.
Negative cells are attracted to positive charged
ions.
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Neural Transmission
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Neurons are linked together in complex
chains.
There is a gap between the axon of one neuron
and the dendrite of another – this is called the
synpase.
Neural messages cross this gap depending on
chemical substances that are called
neurotransmitters.
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Multiple Sclerosis and GuillainBarre Syndrome
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The myelin sheath is a layer of fatty cells that
insulates the axons of some neurons.
Their purpose is to help speed the impulses of
that neuron.
They are important for the normal transfer of
information in the human nervous system.
With MS – the myelin sheaths of axon bundles
in the brain, spinal cord and optic nerves
hardens or develops lesions around those
bundles.
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The Myelin Sheath
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Guillain-Barre Syndrome
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This is a more common demyelinating disease that
attacks the myelin of the peripheral nerves that
innervate muscle and skin.
Often the disease develops from minor infectious
illnesses or even inoculations.
It seems to result from a faulty immune reaction in
which the body attacks its own myelin as if it were a
foreign substance.
The symptoms come directly from the slowing of
action potential conduction in the axons that innervate
the muscle.
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The Addicted Brain
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The human brain is the world’s most prolific
manufacturer and user of drugs
Biochemistry of addiction.
The role of neurotransmitters in mediating
thoughts and feelings, particularly pain and
pleasure.
A rat b/c addicted to cocaine and once addicted,
will choose cocaine over food and thus starve to
death.
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Endorphins
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Endorphins was coined from endogenous morphine
and refers to the brain’s natural painkillers.
Pert & Snyder – 2 researchers – identified “opiate
receptors” in the brain.
The discovery of endorphins grew out of the curiosity
of 2 British pharmacologists, Hans Kosterlitz and John
Hughes. In 1975, they isolated a substance from the
brain of pigs that had the same actions as morphine.
They named it enkephalin.
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Endorphins
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Later, the brain opioids were discovered. The
group as a whole was named endorphins.
Research now looks at how natural opioids are
produced by the brain, the pituitary gland, and
other tissues in response to pain,stress, or other
vigorous exercise.
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Parkinson’s Disease
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Parkinson’s disease was named after James
Parkinson, a London physician who first described
its “involuntary tremulous motion” in 1817
It was hoped that Parkinson’s might be alleviated by
replacing the chemical. It was thought that the
tremors of Parkinson’s disease resulted from the
death of nerve cells that produced dopamine, and
thus the affliction became the first illness attributed
to neurotransmitter deficiency.
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Facts about the Brain:
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At birth, the brain has all the brain cells or neurons
that it will ever have.
Brain neurons do not regenerate.
The environment modifies brain structure.
Neural plasticity – ability to change its structure and
function in response to external experiences.
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Brain Research
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At birth, humans do not yet possess a fully
operational brain.
Environment affects how genes work; genes
determine how the environment is interpreted.
Dr. Marion Diamond at the U. of CaliforniaBerkley, 1960s.
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More Facts about Brain
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The brain develops in an integrated fashion
over time.
Learning is gradual. For ex…a baby doesn’t
learn how to talk in one week.
The brain is curious and seeks connections
between the new and the known.
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More Facts about Brain
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IQ is not fixed at birth.
Intervention programs can prevent children from
having low IQs.
Some abilities are acquired more easily during
certain sensitive periods.
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Applications of Brain Research
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Premature Infants
For example….
Maternal smoking
Alcohol use
Infant malnutrition
Lead poisoning
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Policies
We spend 7x more on
care for elderly than on
children from birth to 5
years old.
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Brain Research
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The role of nutrition of brain function.
How brain chemicals affect mood,
personality, and behavior.
The connection between mind/brain and the
body.
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The developing brain
B – 3 Years
At Birth:
 100 billion neurons
 1 trillion glial cells –
honeycomb that protects &
nourishes the neurons
 Lay out circuits in place.
 Sensory experiences
change brain structure.
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Deprivation of
stimulating
environment leads to
decreased brain
development.
Malleable brain, e.g.
stroke, epilepsy
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Genes and the Brain
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100,000 genes in
human DNA
Some 50,000 genes
appear to be dedicated
to constructing and
maintaining the
nervous system.
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Experience kicks in.
The connections lends
the growing brain
exceptional flexibility
& resilience.
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Neural circuitry & stress
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Children who are physically abused – brains
tuned to danger.
Emotional deprivation – marked reduced
activity in the left frontal lobe.
Physical, emotional abuse / neglect – child’s
brain is forgiving – for a time.
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Emotional deprivation early in life
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The patterns of brain activity displayed by
these children closely tracked the ups and
downs of their mother’s depression.
At the age of three, children whose mothers
were more severely depressed or whose
depression lasted longer continued to show
abnormally low readings.
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Eye
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Children born with a cataract will become
permanently blind in that eye if the clouded
lens is not promptly removed. Why? The
brain’s visual centers require sensory stimulus
to maintain their tentative connections.
Critical period for the eye is 3 years old.
Same holds true for hearing.
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Language
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Many linguists believe that language skills
unfold according to a strict, biologically
defined timetable.
Let’s examine this notion with the case of
Genie.
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Plasticity
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Brains greatest growth spurt decreases at about 10
years old.
By 18, the brain declines in plasticity but increases
in power.
Potential for greatness is encoded in the genes; but
whether potential is realized involves how patterns
are etched by experience in critical years.
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Politics of Biology
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Addictive disorders, sexual orientation, criminality?
Due to nature/nurture.
Research: finding a new gene for lots of things.
E.G., shyness, tendency to divorce, lack of
happiness, etc.
Implications for belief in genes: decreases sense of
responsibility for ailments. E.G., alcoholism –
victim or have control?
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Politics of Biology
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Research for years…to identify genetic roots for
aggression, violence, criminality.
1965 study found imprisoned criminals were more
likely than other people to have extra Y
chromosome.
Research did not turn out to be accurate. XYY men
were less intelligent but not aggressive.
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Genetics & Psychiatric Disorders
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Schizophrenia – past view…resulting from mothers
who were apathetic toward their children. New
view: genetics.
Takes guilt away.
Managed care issues – if due to biology – will only
pay for drug therapy.
Homosexuality studies. LeVay (1991).
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Introduction
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The split brain research –
reported by Gazzaniga
(1967)
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Right versus left
hemispheres:
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Left brain controls the ability
to use language
Right brain controls spatial
relationships, especially those
needed for artistic activities
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Split brain research cont’d
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Many people believe that each half, or
“hemisphere” of your brain may actually be a
completely separate mental system with its
own individual abilities for learning,
remembering, perceiving the world, and even
feeling emotions.
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Research split brain pioneered by
Roger W. Sperry (1913-1994).
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Sperry was a prominent brain researcher and
received a nobel peace prize in 1981 in physiology.
He is best known for his research on “Split brain”
patients, demonstrating how the two halves of the
brain functioned.
He was responsible for overturning the widespread
belief that the left brain was dominant by showing
that several cognitive abilities were localized in the
right brain.
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Sperry
He also provided experimental proof for the
specificity of the reconnection of regenerating
severed neurons in newts, which later led to
new theories on how neurons grow.
 Sperry was born in Hartford, CT in 1913.
 Sperry’s famous split brain experiments started
with the problem of interocular transfer.
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Sperry
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Interocular transfer: if one learns with one eye how
to solve a problem then, with that eye covered and
using the other eye, one already knows how to solve
the problem. This is called “interocular transfer of
learning.”
The question is….how can the learning with one eye
appear with the use of the other? Sperry split the
optic chiasm so the right eye goes to the right cerebral
hemisphere and the left eye to the left hemisphere and
also cut the corpus callosum between the two
hemispheres.
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Sperry
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He did this in cats which created the “split brain cat.”
The cat could be trained with the right eye to
distinguish a triangle from a square while the left eye
was covered.
After the cat learned the problem, Sperry tested the
left eye with the right eye covered. The split brain cat
had to learn all over again. The learning curve for the
left eye (and left hemisphere) was very similar to the
learning curve for the right eye.
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Sperry
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Since the cat had to learn all over from the
beginning with the second eye, the cat could
be trained to pick the square instead of the
triangle when using the second eye. Each
hemisphere has developed a different memory
about what is correct.
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Sperry
Sperry’s experiments with cats and later with
monkeys paved the way for cutting the corpus
callosum in humans as a treatment for severe
epilepsy.
 After the patients recovered from the operation
and were no longer having seizures, they were
generally willing to come to the Sperry lab,
taking part in experiments extending over
several decades.
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Sperry
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What these famous studies taught us:
1.
 2.
 3.
 4.
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Socialness
Lack of Interhemispheric Transfer
Hemispheric specialization effects
Compensary phenomena
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Corpus Callosum
The corpus callosum is a structure made up of
approximately 200 million nerve fibers.
 This structure allows the two hemispheres of
your brain to be in constant communication
with one another.
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Split brain research
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Our increased knowledge of the specialized
functioning of the 2 hemispheres allows us to
better treat victims of stroke or head injury.
By knowing the location of the damage, we
can predict what deficits are likely to exist as
the patient recovers. We can plan appropriate
relearning and rehab strategies to make the
recovery as quick as possible.
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