Transcript Methods of Visualizing the Living Human Brain

Chapter 5
The Research Methods of
Biopsychology
Understanding What
Biopsychologists Do
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Methods of Visualizing the
Living Human Brain
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Contrast X-rays – inject something that
absorbs X-rays less or more than
surrounding tissue
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cerebral angiography
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FIGURE 5.1 A cerebral angiogram of a
healthy subject.
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Methods of Visualizing the
Living Human Brain
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X-Ray computed tomography
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Computer-assisted X-ray procedure
Provides a 3-D representation of the brain
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FIGURE 5.2 Computed tomography
(CT) uses X-rays to create a CT scan of
the brain.
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CT SCANS STROKE
Methods of Visualizing the
Living Human Brain
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Magnetic resonance imaging (MRI)
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High resolution images
Constructed from measurement of waves that
hydrogen atoms emit when activated within a
magnetic field
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FIGURE 5.3 A color-enhanced
midsagittal MRI scan.
FIGURE 5.4 Structural MRI can be used
to provide three-dimensional images of
the entire brain. (Courtesy of Bruce
Foster and Robert Hare, University of
British Columbia.)
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Methods of Visualizing the
Living Human Brain
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Positron emission tomography (PET)
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Provides images of brain activity
Scan is an image of levels of radioactivity in
various parts of one horizontal level of the brain
A radiolabeled substance is administered prior to
the scan
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FIGURE 5.6 A series of PET scans.
(From “Positron Tomography:
Human Brain Function and
Biochemistry” by Michael E. Phelps
and John C. Mazziotta, Science, 228
[9701], May 17, 1985, p. 804.
Copyright 1985 by the AAAS.
Reprinted by permission. Courtesy
of Drs. Michael E. Phelps and John
Mazziotta, UCLA School of
Medicine.)
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Methods of Visualizing the
Living Human Brain
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Functional MRI (fMRI)
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Provides images of brain structure and activity
As with MRI uses strong magnetic field
Structure is imaged using waves emitted by
hydrogen ions
Function is imaged using signal created from
interaction between oxygen and iron in the blood
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BOLD signal
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Methods of Visualizing the
Living Human Brain
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Magnetoencephalography (MEG)
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A measure of neural activity
Measures changes in magnetic fields on the
surface of the scalp
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Created by underlying patterns of neural activity
Fast temporal resolution
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Methods of Visualizing the
Living Human Brain
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Transcranial magnetic stimulation (TMS)
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NOT a measure of neural activity
But provides an experimental probe to alter neural
activity
TMS applies a brief, strong magnetic field that
alters neural activity
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Can either activate or “deactivate” brain structures
Observe changes in behavior
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Recording Human
Psychophysiological Activity
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Scalp electroencephalography (EEG)
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Measure of gross electrical activity of the brain
Uses electrodes attached to the scalp
Many techniques of EEG
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Wave form assessment (e.g. alpha waves)
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Event-related potentials (ERPs)
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Indication of state of consciousness, pathology
Measure activity accompanying psychological
events
Combination of EEG with MRI
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FIGURE 5.8 Some typical
electroencephalograms and
their psychological
correlates.
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Invasive Physiological
Research Methods
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Stereotaxic surgery
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Requires use of stereotaxic atlas and instrument
Lesion methods
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Bilateral and unilateral lesions
Several procedures each requiring careful
interpretation of effects
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Aspiration lesions
Radio-frequency lesions
Knife cuts
Cryogenic blockade
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FIGURE 5.14 Stereotaxic
surgery: implanting an
electrode in the rat
amygdala.
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FIGURE 5.15 A device for
performing subcortical
knife cuts.
FIGURE 5.16 A cryoprobe.
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Invasive Physiological
Research Methods
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Electrical stimulation
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Lesioning can be used to remove, damage, or
inactivate a structure
Electrical stimulation may be used to “activate” a
structure
Stimulation of a structure may have an effect
opposite to that seen when the structure is
lesioned
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Invasive Physiological
Research Methods
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Invasive electrophysiological recording
methods include the following:
Intracellular unit recording
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Extracellular unit recording
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Firing of a neuron
Multiple-unit recording
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Membrane potential of a neuron
Firing of many neurons
Invasive EEG recording
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Pharmacological Research
Methods
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Routes of drug administration
Selective chemical lesions
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Locating Neurotransmitters
and Receptors in the Brain
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Dye or radioactive labels used to visualize the protein
of interest
Immunocytochemistry – based on the binding of
labeled protein-specific antibodies
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Immune response - antibodies created that bind and
remove/destroy antigens (foreign proteins)
In situ hybridization – uses labeled RNA to locate
neurons with complementary mRNA
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Genetic Engineering
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Gene knockout techniques
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Subjects missing a given gene can provide
insight into what the gene controls
Difficult to interpret results – most behavior
is controlled by many genes and removing
one gene may alter the expression of others,
including compensation for missing gene
Antisense drugs block expression of a gene
Gene replacement techniques
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Insert pathological human genes in mice
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Fantastic Fluorescence and the
Brainbow
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Green fluorescent protein (GFP) exhibits
bright green fluorescence when exposed to
blue light
Variants of the gene for GFP can express
other colors
These GFP genes can be inserted into DNA
of neurons—color can then be viewed when
targeted neuronal genes are expressed
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Brainbow
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Behavioral Research Methods
of Biopsychology
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Neuropsychological Testing:
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Time-consuming – only conducted on a
small portion of those with brain damage
Assists in diagnosing neural disorders
Serves as a basis for counseling/caring
Provides information on effectiveness and
side effects of treatment
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Tests of Specific
Neuropsychological Function
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Memory – exploring nature of deficits
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Short-term, long-term, or both?
Anterograde or retrograde?
Semantic or episodic?
Explicit or implicit? (repetition priming tests)
Language – problems of phonology, syntax, or
semantics
Frontal-Lobe Function
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Wisconsin Card Sorting Task
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FIGURE 5.23 The Wisconsin
Card Sorting Test.
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Behavioral Methods of
Cognitive Neuroscience
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Goal is to identify the parts of the brain that
mediate various constituent cognitive
processes
Paired-image subtraction technique:
compare PET or fMRI images during several
different cognitive tasks
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Biopsychological Paradigms of
Animal Behavior
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Procedures developed for the investigation of a
particular behavioral phenomenon
Assessment of Species-Common Behaviors:
Open-field Test
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anxiety, activity
Tests of Aggressive and Defensive Behavior
Tests of Sexual Behavior
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Biopsychological Paradigms of
Animal Behavior Continued
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Seminatural Animal Learning Paradigms continued:
Morris Water Maze
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Spatial learning
Rat must find hidden platform in an opaque pool
Conditioned Defensive Burying
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Following a single aversive stimulus delivered from an object,
rats will spray bedding at the object
Anti-anxiety drugs decrease the amount of burying behavior
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FIGURE 5.26 A radial arm
maze.
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