Transcript How the Brain and Its Disorders Can Be Studied

How the Brain and Its
Disorders Can Be Studied
Karen Law
Massachusetts Institute of Technology
November 21, 2004
History of the Study of the Brain
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There evidence of
brain surgery dating
back to the Neolithic
period (5000 BC)
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Trepanation – skull
surgery
Unearthed remains of
successful brain
operations found in
France
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Franz Gall (early
1800’s)
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Phrenology – bumps
of people’s skulls are
related to their
behavioral
characteristics
FALSE
But an important
concept that different
areas of the brain are
important in different
functions
Case Study:
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Phineas Gage (1848)
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First patient from whom we learned something about
the relation between personality and the function of
the front parts of the brain
Phineas Gage was the foreman of a railway
construction gang. On September 13, 1848, an
accidental explosion of a charge he had set blew his
tamping iron through his head.
The tamping iron was 3 feet 7 inches long and
weighed 13 1/2 pounds. The tamping iron went in
point first under his left cheek bone and completely
out through the top of his head, landing about 25 to
30 yards behind him.
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Amazingly, he still remained conscious and
physically recovered.
 Before the accident:
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capable and efficient foreman
Well-balanced
Shrewd, smart businessman
Sociable
After the accident:
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Fitful, disrespectful
Profane
Impatient and stubborn
Unable to create and stick to future plans
His friends said he was “No longer Gage.”
Techniques to Study Brain
 Lesion
 Ablation
 Electric
Stimulation
 Chemical Stimulation
Lesion and Ablation
 Lesion
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– cut or abnormality in an area
Phineas Gage
Prefrontal lobotomy (1930)
• If frontal lobes disconnected from rest of brain,
violent or extremely emotional mental patients
become calm
• Negative effects: little or no emotion, no social
inhibitions, trouble solving problems

Broca’s (production of speech)
Wernicke’s (understand speech)
 Ablation
– surgical removal of area
Electric Stimulation

Tiny electrodes are implanted in the brain.
There, they can deliver a very mild electric
current that activates that area of the brain
 Experimental:
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applying a current to the appropriate area in a rat's
brain causes the rat to become immediately
aggressive. When the current stops, the aggression
stops.
Olds and Milner (1954) found they could cause rats to
press a bar to deliver electrical stimulation to their
brains. When the electrodes were implanted in the
proper place in the brain, rats would continue to
stimulate themselves for hours.
Treatment:
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Depression
Chemical Stimulation
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Similar to electrical
stimulation, except that
instead of an electrode, a
small tube, a cannula, is
inserted into the brain.
Then, chemicals, usually
crystalline forms of
neurotransmitter, are
introduced into the tube
to stimulate the brain at
the point at the end of the
cannula
Recording Techniques
 Single
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Cell
measures the output of just one neuron.
a small recording electrode is inserted into the
axon of a neuron. Then, that electrode
transmits that cell's activity.
the activity consists of a series of discrete,
similar pulses.
 Electroencephalogram
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(EEG)
records from multiple points on the scalp
simultaneously.
recording the activity of billions of neurons
simultaneously.
the output of the EEG is a complex curve.
research using this technique has proven
especially helpful in studying sleep and
wakefulness
Fig 2. EEG recorded waves
Fig 1. EEG cap
 Biochemical
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Techniques
Biochemical techniques are used to map out
the various neurotransmitter systems in the
nervous system. Depression, for example,
can be linked to levels of neurotransmitter,
and drug therapy for depression alters those
levels.
Imaging Techniques
 Computerized Axial
 Positron
Emission Tomography (PET scan)
 Magnetic
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Tomography (CAT scan)
Resonance Imaging (MRI)
Functional Magnetic Resonance Imaging (fMRI)
CAT Scans
 Uses
X-rays to create images with the aid
of a computer to generate cross-sectional
views of anatomy
 It can identify normal and abnormal
structures and be used to guide
procedures.
 CAT scanning is painless.
 Iodine-containing contrast material is
sometimes used in CAT scanning.
Fig 4. This CAT scan shows a tumor found in the left hemisphere of
a 78 year old man (left). The tumor was taken out surgically
(center). The last scan was taken after ten weeks of recovery from
surgery (right).
PET Scans
 Measures
the brain’s metabolic activity
 Uses small amounts of short lived
radioactive glucose (sugar) as a tracer
Fig 3. PET scans show
the decline in metabolic
activity in an Alzheimers’s
brain (right) compared to a
normal brain (left)
MRI
 Images
internal structures of the body and
brain using magnetism, radio waves, and
a computer.
 The image and resolution of structures
and soft tissue is very detailed.
 An MRI is painless and has the advantage
of avoiding x-ray radiation exposure.
 No known risks.
fMRI
 Measures
change in brain activity in real-
time.
 Relies on the different properties of
oxygenated and deoxygenated blood.
Regions of color show
increased blood flow to
those areas of the brain,
showing more activity
Other ways to study the brain
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Transcranial Magnetic Stimulation (TMS)
 Staining techniques
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To determine the structure of neurons and tissue
layers
Nissl stain
Golgi stain
Brains are Cool!!
Any Questions?