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PSYC 301 > NeuroImaging > Flashcards

NeuroImaging Flashcards

1
Q

Describe X-rays

A

They fire x-rays through a person.
X-ray tube sends x-rays passes through body and hits opposite side on a transistor
Different tissues absorb different levels of rays (produce image based on what its passed through)

Good for a picture of skull at a static moment

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2
Q

What is a cerebral angiography? Describe.

A

A contrast x-ray
Inject iodine into blood which absorbs x rays at higher level, so you get an image during x-ray called angiogram (using high contrast agent)

Get a map of arteries, high resolution

Aren’t pleasant to experience

Can show us distruptions to blood flow: stroke/blockage of flow of an artery (shows where stroke occurs)
Shows hemmoragic strokes too (where is the bleeding)
Shows anurisms: bulbs/extension of arfery and visualize

Most hospitals have this now

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3
Q

What is a CT? Describe it.

A

Computed tomography

  • higher resolution
  • variation of x-ray technique, firing x-rays recieved by a reciever

Fire multiple x-rays and reconstruct the image.

Creators part of EMI record label LOL

Only as good as it’s algorithms (gets better over the years)
Useful for: separating fluid and brain (stroke/damage/lesion shows up as ‘fluid’). Showing tissue/fluid changes, showing where lesions, shows if brain is smaller due to i.e. dementia

Drawback: tons of radiation, especially if you need multiple sessions, not awesome resolution

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4
Q

What is MRI? Describe it, and how it works

A

Structural Imaging
Uses hydrogen atoms and their polarity.
Strong magnetic imaging

they have from 3T-7T-11T (Tesla)
Earth’s magnetism is a fraction of a T

Magnetism so strong, it must always be turned on, cooled to almost absolute zero
Strong safety rules in place

Produces amazing images
- individual slices that are reconstructed, including your face, awesome 3D creation

Lots of hydrogen in human beings (water), will line up in a magnetic field, no physiological harm

HOW IT WORKS:
1) Align protons with a magnetic field
2) Perturb hydrogen atoms with a second varying magnetic field
3) measure energy (radiofrequency RF signal) released during realignment (relaxation)
They relax at slower or faster rates due to density differences in water in different areas

Limited acess to these! Really hard to install
REALLY EXPENSIVE 1000S/HOUR
Structural

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5
Q

What is an overlay plot?

A

Collecting many individuals who have different profiles but all have same issue/symptoms (i.e. amygdala damage, or memory loss)
Do MRI scans and find common areas that hey all have: Can see a more focal image (where they all have common damage)

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6
Q

What is DTI?

A

Diffusion Tensor Imaging
-Variant of MRI
-Relies on how water molecules move in the brain (in WHITE MATTER)
- water in extracellular fluid moves however it wants, but in white matter its limited
DTI looks for movement of contstrained molecules
Shows you where myelinated axons are
limitation: don’t understand how it completely works LOL

BENEFIT: There are many conditions that don’t damage a specific AREA, but the connection between them is damaged. So other scans would show no damage!

No obvious way to see change in grey matter

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7
Q

What is arcuate fasiculous?

A

Connects wernikes and broca’s area. If there is damage here, there won’t necessarily be damage to broca/werneike but you will see deficits because they are no longer connected

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8
Q

Make notes about owen’s research paper

A

do it

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9
Q

How do we look at functional brain scans?

A

Overlain on structural scans :)

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10
Q

What is EEG? Describe it :)

A

Electroencephalography

  • can be done on the cortex
  • measures tiny voltage changes on the scalp and reflects activity of thousands of neurons in the brain
  • many electrodes on brain measuring 100,000s of neural activity

Very fast, temporally awesome
(almost instantaneous)
-faster but coarser than MRI

Gives you brain waves that are linked to states of activity

Portable
Easy to do (on kids too)
Cheap/Easy
A bit spatially ambiguous

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11
Q

What are Gamma and Delta rays?

A

Gamma: observed during intense mental activity
Delta: observed during deep sleep

Different frequencies represent different waves/levels of mental activity

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12
Q

What does your brain do when it is sleeping?

A

Neurons fire less often but more in sync (big amplitudes less often)
Rem is like being awake (vivid dreams)

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13
Q

When are the most intense gamma waves recorded?

A

Monks meditating -

study: brought in monks and students, as they got better, their brains resembled the monks more and more

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14
Q

Describe PET scans

A

Position Emission Tomography

  • functional ‘heat map’ that shows binding effects of radioligants
  • better algorithm, better quality

Radioligants: strong radioactive molecule, created from a Cyclotron (really expensive)
Anything can become a radioligant (glucose: active areas bind more glucose)

Give patient radioactive molecule, that will decay, it will bind to where the normal molecule binds and while its there some of it willl decay (positrons being emitted) and we record the image thats given!

An indirect measure of activity

Long scans (45 mins) so not very good temporal resolution

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15
Q

What is FDG?

A

radioactive glucose

-need a baseline before doing an activity

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16
Q

How do schizophrenic patients differ in FDG activity?

A

Their frontal brain has less FDG activity - hypofrontal

17
Q

What is a mean difference image

A

Subtraction method
Individual performs a task, then in a control condition where they do something unrelated, then you subtract and are left with the activity of the stimulation. Tast-control image.

Issue: brings all the info together and ‘distort’ the brain until they are the same shape, must be lumped together HOWEVER: issue: individual differences look a bit different from each other, and the average won’t align with any of the individuals, not representative of any one brain!!

18
Q

What are the pros/cons of PET?

A

Cons: very expensive (5000/participant)
Temporal resolution is slow (not good, takes 45 mins)
Poor spatial resolutions
Can’t target specific systems - can target REGIONS,

Pros: useful for comparing different conditions, looking at specific systems (DA: dopamine?) or proteins (tau) and useful for lifespan/conditions changes like stroke or CTE.
I.E. showing bindings getting weaker and weaker finding fewer things to bind to. like the dopamine system getting weaker over your lifespan

19
Q

How do you use PET to image Diaschisis?
**
???

A

Diaschisis: when an area itself isn’t damaged, but it has lost inputs from a damaged area
i.e. tissue lost in a stroke, cells in your brain die
but these parts aren’t operating independently within systems, so there will be many inputs and outputs. Anatomical damage may be different than the functional damage , because they aren’t getting input from those lost areas anymore. “hypoactive”

Tissue becomes active again: due to redistribution of axons and gettin it’s inputs elsewhere

20
Q

Describe fMRI

A 
BOLD response
B: blood
O: oxygen
L: level
D: dependent response
Non invasive
Not expensive
Relies on magnet to manipulate hydrogen atoms to align. but measures difference in oxygenated and deoxygenated blood
(they have different magnetic profiles) 
- you can measure this change in the MRI as the balance changes

Inferring brain actiivty from oxygenated levels

Similar to PET scan, anywhere active will need glucose, so oxygenated blood will go there!!

21
Q

How does the BOLD response for fMRI work?

**

A

proxy for brain activity (indirect)

As a synapse is active, it needs more oxygen and more ATP.
Astrocytes get O2 from our blood,
astrocytes play a role and have GLUTAMATE receptors on them, and when you activate them, it triggers dialation of the blood vessels to allow more oxygenated blood to come into an area.
Usually bringing more blood then we actually need, but need sophisticated analysis to detect them.

Glutamate binds to astrocyte glutamate receptors which cause changes in calcium which causes astrocytes to allow more o2 to flow to a brain area

22
Q

What is paired image subtraction?

A

Simple and common, two very similar conditions (one with the thing you’re interested in and the other as a control. Leave behind concept of interest

Quality of your results is related to quality of your controls (if your control wasn’t specific enough you see too much extraneous activity!!

i.e. Teapot

23
Q

What are the problems with interpreting fMRI studies?

* see slides for full descripton

A
  1. Spatial averaging: EPIPHENOMENA - you get an average result that isn’t representative of any of the individuals
  2. Spatial resolution: 3 mm voxels
  3. Temporal resolution: processing happens like 6s after a stim is presented, but in real life you get a huge overlap *
  4. Not necessarily necessary: many areas show up that aren’t important and some are important but don’t show up.
  5. Focus on increase in activity: however some are more active at rest than during the task. Also, some areas just recieve a lot of 02 blood all the time! i.e. hippocampus has high levels of oxygenated blood going through them all the time (experiments have shown when you RELAX you see increase of activity - wandering mind)
  6. Regional hemodynamics: bold responses aren’t universal, need to know the shape of every bold response
    *** BECCA HALP
  7. Confounds: anxiety/boredom
  8. Confounds: drugs (coffee and prescriptions)
  9. Anticipatory hemodynamics: huge issue - when you make someone do a
    task over and over again, you anticipate whats gonna happen, your brain anticipates where blood will be needed and astrocytes will send blood to areas that it thinks youll eed it before it does! This messes with data if you’re looking for data 6s after
  10. Reliability: you don’t always get the same resopnse, often only 30% of voxels showed up
  11. Statistics: each voxel represents a t test, and there often a million voxels. THINK ZOMBIE SALMON - too many false positives. need really strict p values
24
Q

What is the default mode network? How do you measure resting state functional connectivity in MRI?

A

Resting state functional connectivity MRI
Medial prefrontal cortex, Posterior cingulate cortex, lateral parietal cortex.

MEDIAL PREFRONTAL CORTEX*

Chose a region as a ‘seed’ region, (maybe prefrontal cortex), every time they stop activity the prefrontal cortex goes up, so watch and see what other areas do.

When it goes up/down in your seed region, what happens in the surrounding networks? see functional networking - assume areas are working together and in construct.

25
Q

Whats the ‘heavy metal brain’

A

study that said heavy metal music lovers are abnormal ***but it was not lined up with any behavior, look at framing and interpretation, because it can lead to a distressing conclusion

PSYC 301 (11 decks)

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