Neuroimaging Flashcards
what is an xray?
electromagnetic imaging that reveals iamge based on x-ray absorption
what does an xray show?
absorption of x-rays by dif parts of the bodyw
what is cerebral angiography?
using a contrasting agent to reveal blood vessels in teh brain
what contrasting agent?
iodine
what does cerebral angiography reveal? and help diagnose?
blood flow and abnormalities in blood vessels
- stroke and bleeding from strokes
what is CT?
imaging technique that uses x-rays to create 3D image of brain
what does Ct show?
tissue, fluid, stroke, loss of brain tissue, hydrocephalus
what cant CT differentiate ebtween?
gray and white matter - eg brain cancer
what is MRI?
imaging tech - uses magentic fields to crete detailed 3D images of the brain
how does Mri work?
aligns atoms in the body with magnets then applies second layer that momentarily throws the atoms out of order, and watches them go back into order and measures radiofreq signal produced during realignment w/ large magnetic field
- when atoms move and go back, they release a bit of E and that’s measures
- v expensive
what can mri show?
damage from stroe, similar to CT but higher resolution
advantage of mri over ct?
ability to overlay plots and study brain areas in multiple participants
main risk of MRI?
being around strong magnet
what does MRI provide gross overview of?
cranial anatomy and arrangement of neurons
What is diffusion tensor iamging? DTI
viewing white matter tracts
how does DTI work?
- studies water mvoement - extracellular and intracellular
- intracellular follows axons (white matter tracts), while extracellular moves randomly
what is EEG used for?
measures epilepsy and sleep states, non-invasive, easy to implement, but noisy signals
time resolution of EEG?
fast
spatial resolution of EEG?
captures millions/bllions of neurons
limitations of EEG?
noisy and cannot measure deeper brains tructures
dif patterns of sleep stages? (3)
- high freq, low amp = awake
- low frew, high amp = deep sleep
- REM - sim to awake
What is positron emission topography?
measures radioactivity in teh brainho
how does PET work?
person exposed to a radioactive chemical that travels thru blood to brain, scanner picks up on the E released when chem decays = shows where that partic molecule goes in brain
name fo machine needed for PET?
cyclotron
what does cyclotron do?
makes chemical molecules radioactive, expensive as decays quick
what measures indirect activity?
PET and fMRI
PET measures?
glucose or water use in brain
fMRI measures?
blood flow and oxygenation in the brain (BOLD)
BOLD
blood oxygen level dependent
another term for BOLD?
hemodynamic response
spatial resolution o fPET?
poor
diaschisis? temp or perm?
- hypoactivity in brain areas from loss of inputs from damaged areas
- temp dysfunction as indirect damage
mean difference images in PET?
meaningful difs in glucose measurement between stimulation and control conditions
- subtract control from stimulation
fMRI measures in terms of blood?
oxygenated vs deoxygenated
dif magnetic properties between O2’d and deO2’d blood?
they relax at different rate, differential relaxation rates
fMRI measures in terms of braina ctivity?
indirect measure of braina ctivity through blood flow, not measuring APs (so indirect)
what is hemodynamic response measured by fMRI?
- relaxation of molecules in the brain, 6 second delay
how do astrocytes affect blood flow in the brain?
increase CA+ levels in axons
-Ca come in (potent signaling molecule), feet are wrapped around blood vessels to dilate blood vessel
- neurons can’t have direct effect on blood because of BBB, but astrocytes live in both worlds
- axons respond to neuronal signaling
why are controsl important in fMRI studies?
quality of results depends on quality of controls
what is event-related MRI?
measurign variables as they move together across many trialsw
what is regression in fMRI?
examining the rel between a variable and brain activity
- as variable moves, what happens to brain activity - up or down?
5 probs in interpreting fMRI studies? (SSTNF)
1 spatial averaging - average of averages not accurate per se
2 spatial resolution - 1 voxel is smallest and contains tons fo neurons so not super detailed info
3 temporal resolution - building 3D out of 2D limits how many slices you see and from when, delayed
4 not necessarily necessary - jsut because you see activity doesn’t mean its essential to task being explored
5 focus on increasing an activity - some parts are really active (hippo) so might not be able to see when active and brain is super active when relaxed (DMN)
what is resting state functional connectivity?
studying braina ctivity at rest and looking for networks of activity or relationships between dif brain areas
- seed region and compare whenever BOLD goes up in seed region, does it go up in corresponding area?
Problems with interpreting fMRI studies? (5) RCCAR
- Regional hemodynamics - dif brain areas have dif hemodynamic responses so 6 sec measurement would = wrong data
- confounds - anxiety, boredom, claustrophobia, falling asleep all affect brain activity
- confounds - drugs - hard to find someone not affected by some psychoactive drug (caffeine)
- anticipatory hemodynamics - doing repeptitive tasks, brain learns to anticipate, might send O2 there before it normally would in anticipation of reusing same area
- reliability - test re-test for MRI not great, order ~30%
types of structural imaging? (5)
- X-ray, DTI, cerebral angiography, ct scan, MRI,
types of functional imaging? (3)
- EEG, PET and fMRI
what’s difference image?
avg from all participants
- also subtraction method
issue w/ temporal resolution for fMRI?
limited by number of images obtained, 1-2 seconds apart each slice vs APs fire m/s
- great for seeing large patterns fo activity, not smaller
spatial resolution of fMRI?
- difficulty in distinguishing activity w/in a voxel, 10-15 mil neurons per voxel
how is a MRI rep’d statistically?
