fMRI and long term memory

Question 1

What are the safety concerns about an fMRI? (6)

Answer 1

strong magnetic field (induce current in metal objects)

superconductor quench (helium evaporation)

changing magnetic fields (current induction)

radio frequency coil (specific absorption rate, don’t want to use too much of this)

claustrophobia

Noise

Question 2

How many tesla is an fMRI machine

Answer 2

1.5T

Question 3

What is an RF?

Answer 3

“opera singer with wine glass”

matter itself has a frequency in which it absorbs energy (just not sound anymore like opera singer) but in this case
targeting Hydrogen

Question 4

what is a pulse sequence?

Answer 4

A sequence of sending energy in and changing the magnetic fields gradient very quickly

Question 5

what makes in fMRI loud

Answer 5

turning the magnets on and off really fast

Question 6

where the information is coming from in the brain is encoded in terms of what?

Answer 6

frequency

Question 7

when you record the signals what is the initial problem?

how do we solve this

Answer 7

All the signals from all over the brain are mixed together

change it from representing frequency to representing location with a 2D fourier Transform

MATH!

Question 8

a single dot in the K-space image represents what in real space

Answer 8

A series of waves

Question 9

what determines in the image is lighter of darker

Answer 9

it shows the density of Hydrogen in different areas on the brain (proton density) dependent on water

the density is much lower in the air so it is darker

the lighter it is the denser it is

the types of tissue makes a difference too

the properties of tissue change how the energy is released from the matter.

Question 10

how fast dephasing (decay) and recovery happens depends on what?

Answer 10

they tissue type (white matter grey matter)

Question 11

by changing the timing of the RF pulse (TR) or the data acquisition (TE) we can do what?

Answer 11

we can emphasize either the density of protons or other types of tissues such as white and grey matter.

Question 12

T2 weighted imaging shows what?

Answer 12

water very bright

Question 13

T1 imaging shows what?

Answer 13

Grey and white matter stand out from one another and water is black

used most for structural imaging

Question 14

proton density weighted shows what?

Answer 14

whatever has the most hydrogen is the brightest (water)

Question 15

What does BOLD contrast stand for?

Answer 15

Blood oxygenation level dependent contrast

Question 16

How does BOLD contrast work/ dependent on?

Answer 16

oxygenated hemoglobin and deoxygenated hemoglobin respond differently

this is due to the iron

Question 17

how does oxygenated hemoglobin show up in a picture, what are its characteristics? (2)

Answer 17

clear
diamagnetic
zero magnetic moment

Question 18

how does deoxygenated hemoglobin show up in a picture? what are its characteristics? (5)

Answer 18

Blurry

Paramagnetic
significant magnetic moment
greater magnetic susceptibility
causes faster T2 decay

Question 19

neural activity causes what?

Answer 19

Firing, this uses O2 and will make the blood vessels in that one point in the brain to dilate. this will increase the flow of oxygenated blood.

Question 20

neurons fire and at what times does deoxygenated hemoglobin hit a low? what happens at this point?

Answer 20

around 6 seconds

the MRI image is the best

Question 21

when deoxygenated hem. levels go down what happens to the MRI signal?

Answer 21

It goes up, this is due to the deoxygenated hem. interfering with the picture

Question 22

BOLD signal is better for what?

Answer 22

better at representing the local field potential than the actual AP.

better for post synaptic potentials

Question 23

What is the first step in processing fMRI data?

Answer 23

slice timing correction

-need to correct for the fact that different slices are collected at slightly different times

Question 24

What is the second step in processing fMRI data?

Answer 24

Realignment (your head may be moving a little bit)

Question 25

What is the third step in processing of fMRI data?

Answer 25

Reslicing

after realignment we need to reslice to match up Voxels

Question 26

What is the fourth step in processing fMRI data?

Answer 26

Coregistration

align functional images to structural images

Question 27

What is the fifth step in processing fMRI data?

Answer 27

Normalisation

wrap each subject’s brain into a standard template

match all the brains up

do this with softwear

Question 28

what is the sixth step in processing fMRI images?

Answer 28

Smoothing

deal with remaining inconsistencies by smoothing (i.e. blurring) the images

Question 29

what does a fMRI block design allow you to do?

Answer 29

one group gets a fearful face

then a bunch of happy faces

bunch of neutral faces

Question 30

what is an event related design

Answer 30

individual faces one after another all in a random order

mix in some time delays “jittering”

Question 31

what does a mixed design do?

Answer 31

it is a mix between even related and block design