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Lecture 14

PSY 2301 Lecture Notes - Lecture 14: Single-Photon Emission Computed Tomography, Ath, Claustrophobia

Course Code
PSY 2301
Andra Smith

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Name Transcranial
Positron Emission
Magnetic Resonance
Imaging Type Functional Functional Functional Functional Functional Static Static
What it does -Procedure in which a magnet
coil is placed over the skull to
stimulate the underlying brain
-Used to induce/disrupt ongoing
-Turns on neurons in a specific
-Mainly used to monitor patient’s
prefrontal cortex blood flow
-Used as treatment for patients
with depression>stimulates
blood flow in the prefrontal
-Measures the summed graded
potentials from many thousands of
-Reveals features of the brain’s
electrical activity
>The EEG changes as behavior
>An EEG recorded from the cortex
displays an array of patterns, some of
which are rhythmical
>The living brain’s electrical activity is
never silent, even when the person is
asleep or comatose
-use with epilepsy and coma patients
-Event-Related Potentials (ERPs).
>complex electroencephalographic
waveforms related in time to a specific
sensory event
>To counter noise effects, the stimulus
is presented repeatedly, and the
recorded responses are averaged
-Magnetic potentials recorded from
detectors placed outside the skull
-Permit a 3-D localization of the cell
groups generating the measured field
-records magnetic fields produced by
electrical currents
-Imaging technique that detects
changes in blood flow by
measuring changes in the uptake
of compounds such as oxygen or
-Used to analyze the metabolic
activity of neurons
technique that
gathers light
transmitted through
cortical tissue to
image blood-oxygen
-X-ray technique that
produces a static, three-
dimensional image of the
brain in cross section
-Used for head injuries
-Technique that produces a static, three-
dimensional brain image by passing a
strong magnetic field through the brain,
followed by a radio wave, then
measuring the radiation emitted from
hydrogen atoms
-used for mapping the brain function
>motor processing
>somatosensory processing
>visual processing
>auditory stimulation
>higher integrative mental activity
-maeasure of blood flow in the brain
during cognitive, emotional, behavioural
How the MRI works
When the MRI is turned on the radio
freq rotates all the proteins 90 degrees
When the RF is turned off all the protons
go back into alignment with magnetic
The white& grey matter, fatt , tumours
show up because it take all of those
types more time to relax and more
energy. It is shown by contrast
Advantages -Non-invasive -Non-invasive
-Low cost
-# of electrodes can be changed as
-Has a higher resolution than ERP - Spatial resolution = 4-8 mm
-Can detect the decay of
hundreds of radio chemicals,
allows the mapping of a wide
range of brain changes and
-Can detect relative amounts of a
given neurotransmitter, the
density of receptors, and
metabolic activities associated
with learning, brain poisoning,
and degenerative processes
-Used to study cognitive function
Can see how labelled
substances are distributed and
absorbed ie DA, SA
-Can be used on other parts of
the body Ie. Heart
-can be used on children
-Easy to hook
subjects up
-Different head
bands can be used
for investigate other
areas of the brain
-Cheaper and more
accessible than MRI
-fMRI can show functional differences when
no performance differences are present. The
goal may be accomplished but the brain has
done something very different.
Can investigate plasticity of the brain
-A dye can be injected that is non-
-Spatial resolution is superior to
-ability to measure blood flow as neural
activity occurs with almost real time
temporal resolution (6 sec delay)
-repeat imaging is possible
-Performed on standard clinical scanner
Disadvantages -Controversial treatment for
people with depression
-High cost
-Only 4-5 in Canada
-Complicated to operate
-Only looks at eh surface of the brain
-Mathematical equations are used to
determine where the signal(s) come
-Radioactive molecules are
injected into the bloodstream
-Very expensive
-preparaption of the label tracer
-Poor patient compliance for
return imaging
-Poor special resolution
Temporal resolution (minutes to
restricted to cortical
activity (light does
not penetrate the
brain very far)
-Radioactive injection
-resolution not a good as
-baseline – rest is not a good control
-required response device
-movement artifact
-claustrophobia (no sedation possible)
-it is only as good as the task
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