Transcript Techniques to Learn about the Brain and Neural Function

Techniques to Learn about the
Brain and Neural Function
• Studying patients with brain damage linked
loss of structure with loss of function
–Phineas Gage
•http://www.youtube.com/watch?v=9QXI_BxlY7M
–Paul Broca and Carl Wernicke
–Gunshot wounds, tumors, strokes, Alzheimer’s
disease
–>Korsakoff’s Syndrome: caused by B1 deficiency
related to malnutrition or alcoholism
Lesions: damaging the structure
• Allows study loss of function
• Ablation – removal of the structure
– Vast majority of lesion studies are with lab
animals, work is determined by Animal Care and
Use Committees
Organization and Evaluation of Brain
Function
http://www.learner.org/resources/series142.h
tml?pop=yes&pid=1569
Direct electrical stimulation provides
another way to test brain function
• EEG
(electroencephalogram) –
amplified tracing of
activity of a region of the
brain produced when
electrodes positioned in
direct contact with the
scalp transmit signals
about the brain’s electrical
activity to an EEG machine
EEG
• Used to study epilepsy
• Present stimulus repeatedly to a subject and have
it filter out activity unrelated to the stimulus
– conclusion: identification of electrical wave evoked by
the stimulus
– Ex: we can detect where information goes in a cat’s brain
when its whiskers are stroked
Imaging
Techniques
Provide Images of
Brain Anatomy
(CAT/CT and MRI)
CAT Scan/CT Scan
(computerized axial tomography)
1. CAT scan creates
computerized
image of X-rays
passed through
brain
–
–
Creates 2D “slices”
Arranged to show
extent of a lesion
CAT Scans
2. Procedure may involve injection of contrast
dye
•
•
Shorter scanning periods than MRI (no magnets
used)
Used for patients with pacemakers and metallic
implants
MRI
(magnetic resonance imaging)
1. Giant circular magnet causes hydrogen
nuclei in the water of cells to orient in a
single direction
•
•
•
•
Pulses of radio waves cause atoms to spin at a
frequency
Computer constructs images based on these
signals
MRI images more detailed than CAT or PET
scans
Can be produced for any plane of view
MRI: produces the most detailed picture of
brain structure – 3D
Some imaging techniques have
enabled neuroscientists to observe
activity of the brain as it functions.
• fMRI (functional magnetic resonance
imaging)
• PET scans (positron emission tomography)
fMRI
• Capitalizes on MRI ability scanners to detect
changes in oxygen during heightened neural
activity
– Heightened activity = more oxygen used by brain
• fMRI preferred to PET b/c it doesn’t expose
brain to radioactivity
– Magnetic fields pose mild risk, if overused
PET Scans
(positron emission tomography scan)
1.
Ready for this? Here goes…
•
•
•
When neurons are active, automatic increase in blood flow to active regions
of the brain bring oxygen and glucose necessary for respiration
Blood flow changes are used to create brain images when tracers (i.e.
radioactively labeled glucose) injected into the blood of the subject emit
particles called positrons
Positrons are then converted into signals detected by PET scanner
•
•
Glucose concentrates in the areas of greatest activity and the concentration
of labeled substances taken up by the brain tissue
•
•
•
In other words, the positrons almost immediately are destroyed and produce
pairs of gamma particles, and the gamma radiation is detected by the scanner
Revealed in colored computer graphics
This all depends on the amount of metabolic activity in the imaged brain
region
This technique tracks complex series of interactions in different brain areas
associated with specific mental processes
2. PET scans expose subject to radioactivity
Other advances allow neuroscientists
to learn about relationship of
neurological function to behavior
A. BEAM – brain electrical activity mapping
•
Feeds EEG information from numerous recording sites – more
accurate diagnoses of tumors, epilepsy, and learning disorders
B. MEG – magnetoencephalogram
C. SQUID – superconducting quantum interference device
–
Sensitive devices to detect magnetic fields
D. PRONG – parallel recording of neural groups
E. TMS – transcranial magnetic stimulation
F. Gene knock out technology (removal of specific genes from
mice)
How well did you do?
1999 AP Exam #79
Which of the following is a brain-imaging technique
that produces the most detailed picture of brain
structure?
a.
b.
c.
d.
e.
Electroencephalography (EEG)
Magnetic resonance imaging (MRI)
Positron emission tomography (PET)
Computerized axial tomography (CAT)
Electromyography (EMG)
I think my hyperactive 5 year old may have ADD. To make sure that he
is in fact suffering from Attention Deficit Disorder and not epilepsy,
doctors would most likely use which machine to conduct the necessary
tests using strobe lights?
a. MRI
b. CT
c. PET
d. EEG
e. fMRI
If while in an experiment where I am asked to select and defend some
options, I am told that, “Hypothetically, if we were to deceive you, would
you be deceived?” and I answer that I would know if I was being
deceived – and then they deceived me anyway and I did NOT notice it
all, I would be exhibiting
a. Hindsight bias
b. Confirmation bias
c. Change blindness
d. Choice blindness
e. Choice-blindness blindness