fMRI and long term memory

Question 1

what 3 key discoveries does MRI depend on ?

Answer 1

1. computers (control and data analysis)
2. superconductivity (high field strength magnet)
3. nuclear magnetic resonance/quantum mechanics (absorption and release or electromagnetic energy)

Question 2

how does MRI work?

Answer 2

electricity running through it creates a suer strong magnetic field, needs to made of material that is capable of sustaining this conduction. The magnetic field aligns the proton ‘spin’ amongst the water in the human body

Question 3

2 safety concerns of the strong magnetic field

Answer 3

• projectile effect (biggest)

- movement of objects

Question 4

what is the super conductor quench?

Answer 4

helium evaporation- cooled wit helium so that is it conductive but the if breaks it will stop conducting and helium will rapidly evaporate pushing air out of the room

Question 5

6 safety concerns of MRI

Answer 5

1. strong magnetic field
2. superconductor quench
3. changing magnetic fields (current)
4. radio frequency coil (absorption rate)
5. claustrophobia (the head coil)
6. noise

Question 6

energy at specific radio frequencies is absorbed and reemitted by nuclei with non zero spin

Answer 6

nuclear magnetic resonance

Question 7

the amount of signal depends on the property of the tissue, what 3?

Answer 7

1. protein density
2. T2 decay (dephasing) - changes how the energy is released
   - -> normally the H atoms all spinning and then they get oh out phase and then rephase together, the tissue type changes how fast this happens
3. T1 recovery (return to resting state)

Question 8

what else does the signal depend on?

Answer 8

the timing of the RF pulse (TR) and data acquisition (TE)

Question 9

for a given TR and TE, differences in proton density, T1 and T2 produce ______. 3 types

Answer 9

contrast

• proton density weighted
• T1 weighted
• T2 weighted

Question 10

2 properties of oxygenated hemoglobin

Answer 10

1. diamagnetic

2. zero magnetic moment

Question 11

4 properties of deoxygenated hemoglobin

get a blurring image- interferes with the MRI signal

Answer 11

1. paramagnetic
2. significant magnetic moment
3. greater magnetic susceptibility
4. causes faster T2 decay

Question 12

nearby blood vessels get about ___% wider. the blood vessels in the one tiny area of the brain where the neurons are firing
- this allows for?

Answer 12

25

- allows for more oxygenated hemoglobin to that part of the brain (flushes out deoxygenated)

Question 13

reflect action potentials

Answer 13

multi unit activity and single unit activity

Question 14

reflect post synaptic potentials

Answer 14

local field potentials

Question 15

the 5 typical steps in fMRI preprocessing

Answer 15

1. slice timing correction
2. realignment
3. coregistration
4. normalisation
5. smoothing

Question 16

collecting an image from 
the whole brain but we 
dont collect it all at one 
time, we collect slices 
the time from which we 
collect at the top of the 
brain and the bottom of 
the brain is not the same
- so we correct for this

Answer 16

slice timing correction

(all slices are collected at slightly different times)

Question 17

the brain isnt staying in the same spot in the image so we have to correct for this.

Answer 17

realignment

- record how much we had to the brain to get it lined up again

Question 18

6 parameter rigid body transformation (3 translations and 3 rotations) is the typical method for what?

Answer 18

realignment

Question 19

after realignment you need to _____ to match ___

Answer 19

reslice , voxels

Question 20

align functional images to structural image

- uses an affine transformation

Answer 20

• coregistration

Question 21

wrap each subjects brain into a standard space using a linear combination of smooth basic functions

Answer 21

normalisation (each persons brain is a slightly different shape)

Question 22

in normalisation, you segment into ______, ________ and _____, using tissue probablility maps and bayesian estimation

Answer 22

grey matter, white matter, CSF

Question 23

deal with the remaining inconsistencies by ???

Answer 23

smoothing the images (blurring) (4, 7 or 10 mm FWHM)

- giving up pin point accuracy in able to maintain generalization

Question 24

what is the goal for fMRI results?

Answer 24

learn which brain regions are more active in one experimental condition than in another

Question 25

4 caveats of fMRI results

Answer 25

• inhibition or activation? (does not make distinction)
• how much more active ?
• necessary activity?
• different processing or just more processing?

Question 26

processes by which info is encoded, stored and retrieved

Answer 26

long term memory

Question 27

long term memory has both a massive _____ and ______ and 1 common underlying ________

Answer 27

timescale (months years etc), capacity

- representation ( # and strength or synaptic connections)

Question 28

initial creation of memory traces in brain from incoming info

Answer 28

encoding

Question 29

continued organization and stabilization of memory traces over time

Answer 29

consolidation

Question 30

retention of memory traces over time

Answer 30

storage

Question 31

why are we not great at imaging storage?

Answer 31

not active process

Question 32

accessing/using stored info from memory traces

Answer 32

• retrieval

Question 33

possible reorganization and restabilzation of memory traces after retrieval

Answer 33

reconsolidation

Question 34

medial temporal cortex includes?

Answer 34

perihinal cortex, entorhinal cortex and parahippocampal cortex
and feeds into hippocampus

Question 35

the hippocampus in includes?

Answer 35

denate gyrus, CA3, CA1 subiculum

Question 36

trends found from the ‘subsequent memory’ effect and ‘old new’ effect suggest that the perihinal cortex is involved in?

Answer 36

• encoding becuase more active for new words.

- and that it recieves more about indivudal items and what that are (what” pathway.

Question 37

what does the 3 component model suggest?

Answer 37

• perirhinal cortex is involved in ‘items’ – what
• parahippocampal involved in ‘context’ – where
• entorhinal cortex gets info from both and then sends to hippocampus for binding of items and context