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Cognitive NeuroImaging > Quiz 1 Review > Flashcards

Quiz 1 Review Flashcards

1
Q

Logic of Disruption Methods

A

Brain -> Cognition -> Study change in behavior

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2
Q

Logic of Recording Neural Activity

A

Manipulate Cognition tasks -> Cognition -> Brain -> Neural Activity

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3
Q

TMS and TDCS

A

Transcranial magnetic stimulation and Transcranial direct stimulation: Disrupt mental processing by sending electrical currents to the brain.

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4
Q

Goal of recording neural activity

A

Want to measure brain activity: Neurons respond by firing action potential -> measured in firing rates

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5
Q

How are firing rates measured?

A

Number of action potentials per second

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6
Q

Single cell recording

A

Direct measurement of neural activity
Advantage: High temporal and spatial resolution
Disadvantage: requires surgery

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7
Q

Indirect recording

A

Inference is required to interpret the signal

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8
Q

Temporal resolution

A

refers to the ability to tell you exactly when the activation happened ( Temporal = time)

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9
Q

Spatial Resolution

A

refers to the ability a technique has to tell you exactly which area of the brain is active

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10
Q

FMRI

A

Functional Magnetic resonance imaging: When a neuron fires, it uses oxygen -> excessive oxygenated blood is sent to the nearby blood vessels

High neural firing -> more oxygenated hemoglobin locally therefore FMRI measures hemoglobin and infers neural firing.

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11
Q

FNIRS

A

A device emits and detects NIR (both on the same side of the brain) NIR will reflect and can be detected. It is sensitive to changes on the brain surface

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12
Q

EEG

A

Electroencephalography: measures the collective electrical signals from neurons.

MAX 256 ELECTRODES
EEGs measure the electrical signals from different probes located in different areas of the brain but can be distrrted

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13
Q

MEG

A

Induced magnetic signals from the neural activity

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14
Q

EEG OR MEG: Which can be detected in the sulcus?

A

MEG

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15
Q

EEG OR MEG: Which can be detected in the Gyrus?

A

EEG

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16
Q

BOLD Signals

A

Blood oxygenated level-dependent areas of the brain that are more active tend to receive higher levels of oxygenated blood

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17
Q

Which of the techniques has high spatial resolution

A

FMRI

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18
Q

PET SCAN PROCESS

A

1.) Subjects are injected w/ radioactive chemicals
2.)Used radioIsotopes
3.) Positron quickly annihilates w/ an electron to produce gamma rays
4.) PET Measures gamma rays

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19
Q

Advantages of PET SCANS

A

Non Invasive
Medium spatial awareness

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20
Q

Disadvantages of PET SCANS

A

Low temporal resolution
exposed to radiation
short half life
not portable

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21
Q

Advantages of FMRI

A

High spatial resolution
noninvasive
sample multiple locations in the brain

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22
Q

Disadvantages of FMRI

A

Correlation not causation
Expensive
Low temporal
Not portable

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23
Q

Advantages of FNIRS

A

Noninvasive
high temporal resolution
portable
low cost

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24
Q

Disadvantages of FNIRS

A

Low spatial resolution
shallow penetration
correlation not causation

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25
Q

Advantages of EEG

A

High temporal resolution
Noninvasive
low cost

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26
Q

Disadvantages of EEG

A

Low spatial awareness
only records signals from the surface
correlation

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27
Q

Advantages of MEG

A

High temporal resolution
Noninvasive

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28
Q

Disadvantages of MEG

A

Low spatial resolution
costly
correlation

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29
Q

LOC: Lateral occipital complex

A

Visual object detecting and processing

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30
Q

FFA: Fusiform face area

A

Face information visual processing

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31
Q

Different study types for FMRI

A

Comparisons of activation across multiple tasks
Characterization of a single region response
Correlation between behavior and brain
prior experience can have an effect on brain ( Learning experiments)

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32
Q

FMRI VS MRI

A

MRI = Brain Anatomy
FMRI = Brain functions

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33
Q

Criteria of magnetic fields

A

Uniformity
Strength

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34
Q

3 components of a scanner

A

1.) Magnet ( has to be cold, always on, superconductor)
2.) RF Coil (coils are application-specific ( checking brain or knee uses different coils) can be turned on or off)
3.) Gradient coil: weak but rapidly changing gradient to create a gradient in a specific direction

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35
Q

what happens when a proton spins?

A

when the proton spins, it will create a magnetic field bc it has a charge

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36
Q

Angular momentum

A

a quantity given by multiplying the mass of a spinning body by its angular velocity

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37
Q

Magnetic moment

A

The torque exerted on a magnet or a moving electrical charge when placed in a magnetic field

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38
Q

Do all nuclei exhibit NMR Effects?

A

NMR effects require both magnetic moment and angular moment ( at the same time)
- Only odd numbered atomic mass has magnetic moment

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39
Q

Pauli Exclusion principle

A

odd numbered atoms are more unstable

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40
Q

Parallel vs antiparallel alignment

A

Parallel state-> alpha spin state (lower energy) more stable

Antiparallel state-> beta spin state (higher energy) more unstable

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41
Q

Zeeman Effect

A

energy difference btw parallel and antiparallel states increases linearly with the strength of the magnetic field -> spins are more likely to be in parallel state bc the more unstable state may change and become stable

42
Q

Net magnetization

A

Is the difference between the number of spins in the parallel and the antiparallel state (also called bulk magnetization)

43
Q

What are the two planes that can be used to measure net magnetization

A

Longitudinal and Transverse

44
Q

precession

A

Changing in the orientation of the rotational axis of a rotating body

45
Q

What is the longitudinal plane = to?

A

Antiparallel state

46
Q

What is the transverse plane = to?

A

Parallel state

47
Q

T1

A

Measures how quickly the protons realign with the main magnetic field

48
Q

T2

A

Measures how quickly the proton gives off energy as they recover to equilibrium

49
Q

T1 Images

A

characteristics:
fat = bright
water = dark

Sensitive to:
Anatomical details btw gray and white matter)
helpful in detecting vascular change

50
Q

T2 IMAGES

A

Characteristics:
fat = dark
water = bright
blood flow = dark
lesion = white

sensitive to:
anatomical details (csf spaces/ventricles)
lesions (except near csf)

51
Q

T2 FLAIR IMAGE

A

FLAIR: Fluid attenuation inversion recovery

characteristics:
csf = dark
nonfree flowing fluid = bright

Sensitive to:
lesions near csf/ventricles
edema (swelling)

52
Q

Repetition time

A

Interval between successive excitation pulses

  • TR is always greater than TE
53
Q

Echo time

A

Interval between excitation and data acquisition

54
Q

can MRI Machines detect both t1 and t2?

A

No, it can only detect T2 decay and t1 must be derived

55
Q

Larmor equation

A

Governs the frequency of precession
Tells us that for a different resonance of different magnetic field strengths, they will be using a different resonance frequency

56
Q

Slice Excitation

A

Cn be used to differentiate location of precessions

By varying the magnetic and excitation frequency, we can selectively limit the NMR.

57
Q

What are the five steps to slice selection/excitation

A
  1. Cut the volume into multiple slices
  2. By varying the magnetic field in one direction, different slices will have different lamor equations
  3. RF Coil will excite the lamor frequency of the selected slice
  4. record the signal from the scanner for the selected slice
  5. Loop over slices with steps2-4 to get whole volume
58
Q

what do we use frequnecy and phase for?

A

To encode spatial info within a slice
1. Gradient coil creates magnetic gradient during relaxation
2. different locations in the x axis will have different readout lamor frequencies
3. Multiple frequencies excited
4. know the location from the different frequency

59
Q

what can be treated with motion correction?

A
  1. Head motion leads to fake activation (most noticeable at edges)
    2.) Regions of interest shift over time
60
Q

what cannot be treated with motion correction?

A

Signal distortions due to motion of head

61
Q

issue with motion correction algorithms?

A

Can introduce artifacts that weren’t there originally

62
Q

When should you test more participants?

A

When studying clinical populations
when data loss is likely
behavior correlations

63
Q

what are the hidden costs of underpowered studies?

A
  • Likelihood of false positives
  • researchers time trying to make sense of marginal effects
  • delays during review process
64
Q

what do we use subtraction logic for?

A

To isolate some specific cognitive functions that we are interested in.

65
Q

Mental chronometry

A

Uses reaction times to infer cognitive processes

66
Q

How do we control the mental operations that subjects carry out in the scanner?

A
  1. Manipulate the stimulus ( for automatic mental processes)
  2. Manipulate the task (for controlled processes)
67
Q

what are the three different types of confounds?

A

attentional
motor
eye movement

68
Q

Dorsal attention network

A

helps orient attention in a goal-directed manner

69
Q

Ventral attention network

A

detects stimuli and triggers reorientation to them

70
Q

How to deal with attentional confounds:

A

Fixation: reduces eye movement confound
One back task: hit a button when a stimulus is repeated
Detection/discrimination task: hit a button when stimulus is present

71
Q

How to deal with motor confounds:

A

GOAL: Have equal number of responses across all conditions

have motor responses unrelated to task at hand

72
Q

How to deal with eye movement confounds:

A
  1. require participants to maintain fixation throughout the experiment
  2. let participants free view but record, quantify and compare eye movements across conditions
73
Q

when are errors in HRF models most problematic?

A

In the undershoot phase

74
Q

what happens if the model HRF doesn’t fit the data well?

A

Our estimated activation will not be estimated well and our residuals will be higher

75
Q

what are the problems and solutions of repeating sequence block design?

A

Problem: there might be order effects
Solution: counterbalance with another order
Problem: if you lose a run due to head motion for example, you lose counterbalancing

76
Q

what are the problems with random sequencing:

A
  1. Randomization can be flukey
  2. spend a lot of time defining protocols for analysis to have different randomizations
77
Q

Pros and cons of Regular baseline block design

A

pro: w/ event related averaging, regular baseline design provides clear time courses
Problem: Spend half the time collecting the condition you care the least about

78
Q

Slow event related design pros and cons

A

Pros: useful for designs with motion artifacts (grasping, swalling)

analysis is easier to isolate

cons: low statistical power
subjects get bored

79
Q

Block design

A

Have good detection and poor estimation

80
Q

Slow event related designs

A

Good estimation but poor detection

81
Q

why should we jitter>

A

yields larger fluctuations in signal

82
Q

How do we jitter?

A

Include 1-2 null trials between real trials

83
Q

sequence

A

for n # of conditions there are n^2 ways that the conditions could follow each other

84
Q

when can you not counterbalance?

A

when subject errors mess up counterbalancing, decision making where someone chooses choice 1 or 2, correlations with behavior, and memory experiments

85
Q

Pros and cons to Rapid ER Design

A

Pros:
* high detection power
* trials can be put in unpredictable order
* subjects don’t get bored

Cons:
* reduced detection compared to block designs
*requires stronger assumptions about linearity (but bold signals aren’t super linear)
*errors in hrf can introduce errors in activation estimates

86
Q

what condition shows the clearest data?

A

Higher effect with lower noise

87
Q

what does R^2 tell us (the correlation)

A

Tells you how much noise is in the data and how well the correlation between the predictive model and the raw signal

88
Q

what is a type 2 error?

A

Incorrect rejection: occurs when there is a real activation difference in a given voxel but the statistical test does not indicate activation

89
Q

What is a type 1 error?

A

False positive: no real activation difference but statistical test indicates there is

90
Q

Issue with Bonferroni correction:

A

Assumes each voxel is independent of others which is not true

91
Q

Step by step of cluster correction:

A
  1. choose cluster defining threshold
  2. estimate smoothness of maps
  3. run monte carlo stimulations
  4. set a minimum cluster size (k)
92
Q

How to use GLM for FMRI DATA

A

Adjust the height of the predictor(slope) and the constant (intercept) to best fit the data

93
Q

what does the slope determine?

A

Whether the manipulation is good

94
Q

what is a beta weight?

A

Size of difference

95
Q

Talairach coordinate system:

A

Based on alcoholic old lady, any brain can be squished or stretched to fit hers

96
Q

What is the first step to normalizing the brain into the system?

A

Rotate the brain into the anterior and posterior commissure and make sure both are aligned

97
Q

what are x, y, z

A

X = LEFT/RIGHT
Y=ANTERIOR/POSTERIOR
Z=SUPERIOR/INFERIOR

98
Q

mni space

A

Based on many subjects, using nonlinear warping for transformations

99
Q

Which space provides brodmanns area?

A

Only tal

100
Q

steps for cortical flattening:

A
  1. inflate the brain
  2. make cuts along medial surface
  3. unfold the medial surface so the cortical surface lies flat
  4. correct the distortions so that the distances are preserved
101
Q
A

Cognitive NeuroImaging (1 decks)

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