Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MC > Task 5 > Flashcards

Task 5 Flashcards

1
Q

What does an MRI meassure ?

A 
Structural imaging (no activation) 
-> just pyhsical properties (grey vs white matter)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How does an MRI work ?

A

Look at sheet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does MRI Relie on ?

A

Water molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How is a Water Molecule constructed ?

A
  • > Hydrogen atom and Oxygen atom

- > Hydrogen atom have a magentic propertie

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does a Hydrogen atom consist of ?

A

-> Proton

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a proton ?

A
  • > Unsynchronized Spinning charged particle

- > Oriented randomly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens if you apply a stong magentic field ?

A
  • > High energy protons point downwards (antiparallel)

- > Low energy protons point upwards (parallel)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens if you apply a brief readio frquence impulse?

A
  • > Turns Low energy protons to high energy protons (90 degree switch)
  • > Protons move now synchronized
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the effects of synchronized protons?

A

-> Produce a detectable magenetic field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens when the redio frequency stops ?

A

-> Protons will be pulled back into original allingment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two types of meassurment in an MRI scan ?

A
  • > T1 / T2

- > T2 *

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does T1 and T2 meassure ?

A

T1 = meassure the anatopical properties
-> how much time is needed for the previously low energy protons which changed to high energy protons due to the RF pulse to change back to low energy protons
-> Grey matter and white matter vary in timing on how much they spin back
T 2 = how much time till the presscsion spins randomly again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does T2 * meassure ?

A

-> meassure functional property

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does functional imaging mean?

A
  • > Always a hemodynamic response
  • > Indirect measurement (look at the consequences of neurons firing)
  • > How good can methods measure function
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does Hemodynamic mean?

A
  • > When the activity of neurons increases, the blood supply to that region increases relatively to others
  • > providing it with more glucose & oxygen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the limitations of functional imagaing ?

A
  • > Poor temporal resolution

- > To relate function and structure, must map data of fMRI & PET onto corresponding MRI scans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How does Pet work ?

A
  • > inject radioactive tracer into bloodstream

- > Tracer measures local variation in blood flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does the tracer meassure local variation in blood flow?

A
  • > Tracer are most often isotope consiting of a positron and a oxygen molecule
  • > The positron correlates with an electron
  • > The collison releases two gamma rays
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Where is Pet most oftenly used ?

A
  • > It can measure the concentration of creatin molecules or pathways
  • > Alzheimer molecule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the assumption of PET scan ?

A

-> More active region receive more tracer since they need paired molecule oxgen !

21
Q

How does an fMRI work?

A
  • > Active regions need oygenated hemoglobin
  • > When neurons consume oxygen it get converted ito deoxyhemoglobin
  • > High lvl of Oxygen are detected with fMRI via sending in multiple electrical fields
  • > oxygen and deoxygen have different magentic properties
22
Q

Explain the Hemodynamic Response function:

A
  1. Intial dip = Higher deoxy hemoglbion
  2. Overcompenatsion = increased in blood flow is greater then consumption (6 - 10)
  3. Undershoot -> Bold signal decrease higher doexgynated
23
Q

What is meant by bold ?

A

the ratio of oxygenated to deoxygenated hemoglobin

24
Q

What is important for an fMRI design:

A

-> Be aware of when you present a stimuli since oxygen lvl must be at baseline

25
Q

What is something you need to look out for in an fMRI scan ? Before you scan !

A
  • > Correction for head movement

- > If the head moved the postion of active region also moves

26
Q

What do you need to be aware of after the fMRI Scan ?

A
  • > Steretatctic Normalization
  • > Smoothing
  • > Statistical Comparison
27
Q

What is meant by Steretatctic Normalization ?

A
  • > It is the process of mapping regions on each individual brain onto a standard brain via stretching or squashing
  • > Brain gets divided into thousands of voxels which are given Talairach coordinates (x,y,z)
28
Q

What does the X coordinate refer to ?

A
  • > Left and right

- > Left is negative right is positive

29
Q

What does the Y coordinate refer to ?

A
  • > referes to front and back

- > Front is positive and back is negative

30
Q

What does the Z coordinate refer to ?

A
  • > refers to top and bottom

- > Top = is positive and bottom is negative

31
Q

What is menat by smoothing ?

A
  • Spread some of the raw activation level of a given voxel to neighbouring voxels
  • > The closer the neighbour the more activation it gets
32
Q

What are the benefits of Smoothing ?

A
  • > Enhances SNR (signal to noise ratio)
    1. isolated voxel = (noise) gets turned off
    2. Signal = Cluster activity
33
Q

What is meant by statistical power ?

A
  • > “is the mean activity at a particular voxel greater in the experimental condition than in the baseline condition?”
  • > Usually treshold must be lower then 0.05
34
Q

What are data interpretation ?

A

-> Activation in image is the difference between two conditions (Task A – Task B)

35
Q

What is the problem of fMRI activation?

A
  • > Just because one region is active, it doesn’t mean it’s essential for the task
  • > Activation can either mean inhibition or excitation
36
Q

How to increase the spatial resolution of fMRI ?

A
  • > higher tesla
  • > Increasing voxel size = lowering spatial rsolution
  • > reducing voxel size = increasing spatial resoultion
  • > Higher spatial rsolution comes of the coast of less temporal resolution
  • > Spatial resolution = dependent on voxel
37
Q

How to increase temporal resolution ?

A
  • > Time to repetition (TR)
  • > Time betweeen to excitation pulses
  • > Shorter time between impulses = higher temporal resolution
38
Q

How to increase both spatial / temporal resolution in an fMRI study ?

A
  • > Via jittering

- > Parallel imaging

39
Q

What is meant by jittering ?

A

-> Different delays between the start of the sampling of the brain volume images relative to the start of the stimulus presentation

40
Q

Name some factors about fMRI:

A
  • > Based on blood oxygen conectartion
  • > No radioactivity
  • > Participants can be scanned multiple times
  • > Less expensive
  • > Better spatial resolution
41
Q

Name soe factors about PET:

A
  • > Based on blood volume
  • > Involves radioactivity
  • > Partcipants can only be scanned once
42
Q

Which type of protons do we use in an fMRI scan ?

A

-> Protons which alling (cause they add up) due to magnetic field of scanner

43
Q

But what do we actually meassure in an FMRI ?

A
  • > The precission has the speed of mega herz which is in the radio frequency range
  • > increases via higher tesla (lamour equation)
  • > the radio frquency pulse makes the precession equally fast plus it chnages the position of protons
44
Q

Explain how we see the different clouors (grey vs white):

A
  • > More protons = more spinning = white

- > less protons = les spining = grey

45
Q

Oxygenated blood lead to ?

A
  • > high fmri signal
  • > does not have a magnetic field
  • > slow decrease in spinning T2
46
Q

Deoxygenated blood lead to ?

A
  • > low fmri signal since they have their own magnetive field
  • > fast decrease in spinning T2
47
Q

What are drifts ?

A

-> really low frequencies which we want to filer out

48
Q

What does temporal smoothing remove ?

A

-> high frequency signals

MC (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions