Transcript File - Ms. G`s Classroom

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The oldest method of brain study was observation of specific
brain diseases and the results of brain injuries.
Today, in the lab, scientists can lesion (destroy) small clusters of
brain cells, leaving the surrounding tissue unharmed and
observe changes in brain function.
These clinical observations and lab experiments have enabled
us to link structure with function of the brain.
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Phineas Gage (1848) Level headed
and calm railroad foreman suffered a
horrific damage to his brain when an
explosion hurled an iron rod through
his head.
o Cage survived the accident.
o His behavior became impulsive and
he was unable to control his
emotions or his obscene language.
o An autopsy revealed a loss of tissue
where the limbic system is
connected to the frontal lobes,
linking the role of the two in
controlling emotional behavior.
phineas gage
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AN EEG is an amplified readout of the electrical activity of brain
waves from neuronal impulses.
By presenting a stimulus repeatedly and having a computer filter
out brain activity unrelated to the stimulus, one can identify the
electrical wave known as an evoked potential that has been
induced by the stimulus.
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CAT or CT scan creates a computerized image using x-rays
through various angles of the brain showing 2 dimensional slices
that can be arranged to show the extent of a lesion in the brain.
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PET scans can produces color computer graphs that depend on the
amount of metabolic activity in the imaged brain region
When neurons are active, an automatic increase in blood flow to the
active regions of the brain bring more oxygen and glucose necessary
for cellular respiration.
Blood flow changes are used to create brain images when radioactive
tracers (tagged glucose) injected into the blood of the patient emit
particles called positrons, which
are then converted into signals
detected by the PET scanner to
produce a visual image display
of brain activity while the brain is
performing a specific task
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Use magnetic fields and radio waves to produce computer
generated images of soft tissues, including the brain.
MRI scans are frequently used to study brain anatomy.
ventricles
healthy brain
schizophrenic brain
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FMRI (functional magnetic
resonance imaging) can reveal
brain structure AND function.
It shows the brain at work at
higher resolution than a PET
scan.
Changes in the oxygen in the
blood to an active brain area
alters is magnetic qualities,
which is then recorded by the
fMRI scanner.
After further computer processing, a detailed picture of
local brain activity emerges.
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Triune Brain: One model of evolution with respect to the brain.
o The human brain has three major divisions, overlapping
layers with the most resent neural systems nearest the front
and the top.
o The reptilian brain, which maintains homeostasis and
instinctive behaviors, roughly corresponds to the brainstem
(hindbrain).
o The old mammalian brain corresponds to the limbic system,
including the thalamus, hypothalamus, septum,
hippocampus, amygdala, and the cingulate cortex
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The new mammalian brain or neocortex (cerebral cortex)
accounts for about 80% of the brain volume and associated
with high functions of judgment, abstract thought, decision
making, language and computing, foresight, insight,
hindsight, sensation and perception.
Old Mammalian brain
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The oldest part and central core of the brain, beginning where
the spinal cord swells at it enters the skull
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The brainstem is an
extension of the spinal cord
and includes the medulla
and the pons.
The thalamus (not part of
the brainstem) sits on top
of the brainstem as
pictured.
The reticular formation
extends from the spinal
cord to the thalamus
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The brainstem is the crossover point where most
nerves to and from each side of the brain connect
with the opposite side.
The first swelling a the base of the brainstem is the
medulla.
• Center for all involuntary muscle control such as
heart, arteries, digestive system, and diaphragm.
Above the medulla is the pons.
• connects the upper and lower parts of the brain;
serves as a message station between several
areas of the brain.
• key role in sleep and dreaming, (REM sleep)
where dreaming is most likely to occur
Contralateral
nature of the
brain
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Inside the brainstem (between your ears) lies the reticular
formation, a finger-shaped network of neurons that extends
from the spinal cord to the thalamus.
• Some sensory information from the spinal cord travels
through the reticular formation, which filters this
information and relays important information to other
parts of the brain
• In 1949, experimentation with electrical stimulation of
the reticular formation of a sleeping cat produced
immediate arousal.
• Conversely, when reticular formation was severed, cat
lapsed into a permanent coma
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The thalamus sits on top of the brainstem.
It is a pair of egg shaped structures that
function as the brain’s switchboard.
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The thalamus receives messages from all the
senses except for smell and routes them to the
brain’s regions that deal with seeing, hearing,
tasting, and touching.
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The thalamus also receives some of the cortex’s
interpretations or replies and directs these
messages to the cerebellum and medulla.
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Extends from the rear of the brainstem, ball-shaped, two halves
that are wrinkled (cross section looks like a cauliflower or tree)
Coordinates voluntary movement and balance
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Enables nonverbal learning and memory
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Recent studies indicate that the cerebellum also helps us to
judge time, modulate our emotions, and discriminate sounds
and texture.
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These older brain functions all occur
without any conscious effort; we are
aware of the results of our brain’s efforts
but not of how the brain constructs these
results.
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Doughnut –shaped, between the cerebral hemispheres and the
brainstem. Made up of the:
• Hippocampus: processing of conscious memories. People who
lose their hippocampus to injury or surgery lose their ability to
form new memories of facts or events.
• Amygdala: 2 lima bean shaped clusters that influence fear &
aggression including the perception of these emotions and the
processing of emotional memories
• Hypothalamus: lies below the thalamus, contain neural clusters of
cells that direct important maintenance activities such as thirst,
hunger, sex drive, & temperature to help maintain internal
homeostasis (steady internal state)
The only part of the brain that secretes hormones which
influence the pituitary gland and its secretions. amygdala & teens
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Nucleus accumbens
• Located in front of the hypothalamus
• Along with the hypothalamus, appear to be involved in
our reward centers; mediated by dopamine.
• some researchers believe that addictive disorders such
as alcohol or drug dependence or binge eating may be
related to malfunctions in natural brain systems for
pleasure & well-being.
Reward Deficiency Syndrome: people who are
genetically disposed to this syndrome, may crave
whatever provides the missing pleasure or relief from
negative feelings.
pleasure centers brain
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Cerebrum is the largest and most prominent part of the human
brain and constitutes 4/5 of its weight.
It is split longitudinally into two large, prominent left & right
hemispheres separated by a deep median fissure called ‘cerebral
fissure’.
Corpus callosum: large band of neural fibers connecting the two
brain hemispheres that carries messages between them.
Each hemisphere is further divided into the frontal, parietal,
temporal, and occipital lobes divided by prominent fissures (folds)
The basic function of the cerebrum is to control voluntary
functions and seat of intelligence, will power, memory, reasoning,
thinking, learning, emotions, & speech
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Frontal Lobes: lie just behind the forehead, involved in
speaking, muscle movements, making plans, and
judgments.
Parietal Lobes: lie at the top of the head behind the frontal
lobes; involved with sensory input for touch and body
position,
Occipital Lobes: lie to the back of the head; includes visual
areas, which receive visual information from the opposite
visual field
Temporal Lobes: lie roughly above the ears; includes the
auditory areas, each of which receives auditory information
primarily from the opposite ear.
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The Cerebral Cortex is the intricate covering of interconnected
neural cells, that form a thin surface layer on your cerebral
hemispheres.
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Contains some 20-23 billion nerve cells supported by nine
times as many glial cells that guide neural connections,
provide nutrients, mop up ions and neurotransmitters.
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The cerebral cortex is the body’s ultimate control and
information-processing center. Much of the neural activities of
the cerebrum take place within this layer.
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The outer surface is highly convoluted, increasing the
surface area of the cerebral cortex. The ridges of these
convolutions are called ‘gyri’ and depressions between
them as ‘sulci’.
Each region is responsible for a particular function.
According to the function or activity, these regions can be
divided into three general categories: motor, sensory, and
associative.
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Cerebral cortex is a part of the cerebrum.
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Cerebrum is the largest and most prominent part of the
brain whereas cerebral cortex is the outer layer of the
cerebrum.
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Cerebrum has both gray and white matter while the gray
part of it is considered as the cerebral cortex.
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Human cerebral cortex is made up of approximately 10
billion nerve cell bodies and their dendrites whereas the
cerebrum has both cell bodies and nerve fibers.
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Motor Cortex: the area at the rear of
the frontal lobes that controls
voluntary movement
Contralateral function: when tissue of
the motor cortex is stimulated on the
left hemisphere, the right body part
responds (same for the right motor
cortex)
In the motor cortex, the brain devotes
more tissue area to sensitive body
parts and to areas requiring precise
control (such as the fingers & mouth)
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Sensory Cortex: the area in the front of the parietal lobes that
registers and processes body touch and movement
sensations.
The more sensitive a body region, the larger the area of the
sensory cortex devoted to it.
Visual Cortex: receives visual
input from the retina.
Auditory Cortex: receives input
from the ear on the opposite
side of the brain.
The brain devotes more tissue to sensitive areas & areas requiring precise
control so, for example, the fingers have greater representation in the
somatosensory and motor cortex than the upper arm.
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BCI is a collaboration
between a brain and a
device that enables
direct communications
pathway between the
brain and the object to
be controlled.
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Cognitive Neural
Prosthetics: BCI for
people who suffered
paralysis or amputation
BCI
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Association areas are parts of the cerebral cortex NOT involved
in primary motor or sensory functions.
These areas are involved in higher metal functions such as
learning, remembering, thinking and speaking.
Since these areas are so vital to higher order thinking, the saying
that “we use only 10% of our brains” is completely false.
Association areas are found in all four lobes
In the frontal lobes, these areas play and executive role in
judgment, planning, and the processing of new memories.
Association areas in the parietal lobes are involved with
mathematical and spatial reasoning.
A small area on the underside of the temporal lobes are involved
in the recognition of faces.
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Plasticity: the brain’s capacity for modification, as evident in
brain reorganization following damage, particularly in children.
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If one hemisphere is damaged early in life, the other
hemisphere will pick up many of the damaged sphere’s
functions. Neurogenesis: the growth of new neurons
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Plasticity decreases as a person ages, although nearby
neurons may partially compensate for damaged ones after a
stroke or other brain injury.
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It is because of the brain’s plasticity that blind or deaf people
appear to compensate by having other enhanced senses to rely
on.
brain plasticity
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Lateralization of the brain: Clinical observations more than a
century ago, found that the left hemisphere is critical for
speaking, writing, arithmetic reasoning, and understanding.
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Corpus Callosum: a large band of neural fibers connecting the
two brain hemispheres that carries messages between them.
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Split Brain: a condition in which the two
hemispheres of the brain are isolated by
cutting the corpus callosum and other
connecting fibers between them.
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Information from the left half of
your field of vision goes to your
right hemisphere and
information from the right half of
your field of vision goes to your
left hemisphere.
The data received by either
hemisphere is quickly
transmitted to the other side via
the corpus callosum.
In a split brain patient (severed
corpus callosum,) this
information sharing does not
take place.
split brain
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Left brain thinking is verbal and analytical.
Right brain is non-verbal and intuitive, using pictures rather
than words (visual perception and emotional recognition)
Together, the left and right hemisphere make unique
contributions to the integrated functioning of the brain.