Clinical Neuroscience Techniques Flashcards
What are 6 techniques for studying brain structure and function?
- Computerized Tomography (CT)
- Magnetic Resonance Imaging (MRI)
- Electroencephalogram (EEG) / Event Related
Potentials (ERP) - Positron Emission Tomography (PET)
- Functional MRI (fMRI)
When was Computerized Tomography develop?
Developed in 1970’s
What images does CT scan provide?
Static anatomical images of the brain
What does the X-ray source do in a CT scan?
X-ray source emits a series of narrow x-ray beams and
rotates around the head
What positional information can we get from the CT scan?
Many positions and reconstructs a 3-D image of brain using mathematical techniques
In computerize tomography image is produced because different substances ______________________________________.
absorb different amounts of X-rays
CT scan shows that dense tissue:
absorbs a lot of rays -> light image
e.g. Bones
Acute blood
CT scan shows that soft tissue:
absorbs fewer rays -> dark image
CSF
Brain tissue (density of gray matter > white matter)
Infarct
Cysts
What can be used in CT scan to increase contrast for the images?
Intravenous injection of dye may be used to increase contrast (may allow blood vessels, tumors to be seen)
What are the advantages of CT scan? (4)
* Provides what?
* Can be used in?
* Indicates?
* Invasiveness?
- Provides structural image of brain in vivo
- Can be used in healthy and clinical subjects
- Indicates areas of brain abnormality
- Relatively non-invasive
What are the disadvantages of CT scans? (3)
* Resolution?
* Doesn’t provide what?
* Price and requires what?
- Relatively poor spatial
resolution - Provides measure of
structure, not ongoing
activity - Expensive and requires
highly trained specialist
staff
MRI and CT scans have in common that they provide:
Static “slice” images of brain,
but in even greater anatomical detail
In MRI, the images result from effects changing __________________________________________________.
strong magnetic fields applied to brain tissue
What happens with the nuclei of certain atoms in brain tissue in MRI?
Nuclei of certain atoms in brain tissue
(usually hydrogen) align themselves in
orientation of field when the subject is placed in the magnetic field.
What happens with hydrogen atoms when specific radio frequency (RF) is INTRODUCED during the procedure?
Causes hydrogen atoms to
resonate and change axis of alignment
What happens with hydrogen atoms when specific radio frequency (RF) is REMOVED during the procedure?
Hydrogen atoms
“relax” and return to original alignment
What occurs in MRI with hydrogen atoms and RF? (3)
- During realignment, hydrogen atoms discharge the RF energy that they had absorbed
- Because hydrogen (i.e., H2O) composition of different brain structures varies, the RF energy
given off is distinct for different structures - Computer analyses construct 3-D image of brain based of differential energy emissions
Rate at which hydrogen atoms realign and return to a lower energy state is called __________ in MRI.
relaxation
What are the two types of relaxation in MRI?
T1 and T2 which result in 3 main types of images
In MRI T1 images provide: (2)
Dark CSF, light tissue
Pathologies generally behave like CSF (i.e., dark on T1 and bright on T2)
In MRI, T2 images provide: (2)
Light CSF, dark tissue
Pathologies generally behave like CSF (i.e., dark on T1 and bright on T2)
What are the advantages of an MRI? (4)
*Resolution?
* Visualization of brain?
* No use of what material?
* invasiveness?
- Excellent spatial resolution (about 1 mm; determined
mainly by magnet strength) - Brain can be visualized in any plane
- No X-rays or radioactive material used
- Safe, painless, non-invasive
What are the Disadvantages of an MRI? (4)
* Price?
* Where?
* Can’t be used with who?
* What measure does it not provide?
- Even more expensive than CT
- Special housing required for magnetic field
- Cannot be used in patients with metallic devices (e.g.,
pacemakers, vessel clips) - Provides measure of structure not ongoing activity
What does EEG stand for?
Electroencephalogram (EEG)
What does the EEG record?
Records electrical activity of brain by
electrodes placed on scalp
In EEG, the signal is generated by ________________ activity of millions of _____________ cells of layer V and Vl . Signal is amplified and seen as ____________.
Post-synaptic activity of millions of
pyramidal cells
Seen as waveforms
In EEG, beta rhythm of an alert participant (_____________, ________________) will have waveforms of _____________________ amplitude
Awake, Excited
Low amplitude
In EEG, alpha rhythm of an calm participant (_____________, ________________) will have waveforms of _____________________ amplitude
Relaxed, Resting
high amplitude
Why do we use EEG?
Used to diagnose epilepsy and other brain
abnormalities
Event-Related Potentials ERP show:
change in EEG signal in response to sensory
or cognitive stimulus
What are the advantages of EEG? (5)
* Non-invasive or invasive?
* Resolution?
* Record of brain activity?
* Can measure what?
* Price?
- Non-invasive
- Excellent temporal resolution
- Can be used to record brain electrical activity in real time
- Can be used to measure brain’s response to a number
of sensory or cognitive variables - Relatively cheap
What are the Disadvantages of EEG? (4)
* Localizing functions?
* Record of neurons?
* Brain activity?
* Susceptible to what?
- Poor at localizing function
- Activity is recorded from millions of groups of neurons
- Brain activity may fluctuate unpredictably
- Susceptible to movement artifact
What does Positron Emission Tomography (PET) provide?
images of brain function
What is the subject injected with for the PET scan?
radioactive substance (e.g.,
2-deoxyglucose)
In PET scan, ________________ transported by blood to brain and metabolically-active areas will use more ________________ and become more ____________
Glucose
Glucose
Radioactive
In PET scan, amount of gamma radiation
is represented in ____________ images which
indicate those regions which are__________
in metabolism
color-coded
high or low
Which method is used in PET and other functional techniques to make conclusions on brain activity?
Subtraction method
(Brain is always active
so need to subtract
normal background
activity (i.e., control)
from activity
measured during task
(i.e., stimulation))
What are the advantages of PET? (3)
* Measure of?
* When can we use it?
* Resolution?
- Measure of regional
brain activity in vivo - Can be used to measure
brain activity during task
performance - Relatively good spatial
resolution (3-8 mm)
What are the disadvantages of PET? (4)
* Invasive or non ?
* Resolution?
* Tasks?
* Price?
- Invasive
- Poor temporal
resolution (blood flow is
slower than neural
transmission) - Tasks must take longer
than 1 minute - Expensive
What does fMRI measure?
Uses MRI technology, but measures brain activity
What happens in fMRI? (3)
- Active brain areas receive more oxygenated blood
- Concentration of oxygen affects magnetic properties
- MRI can detect functionally induced changes
in blood oxygenation
Compare fMRI to PET and EEG. (2)
- Compared to PET, fMRI has better spatial and temporal resolution
- Poorer temporal
resolution than EEG)
