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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
Advantages of EEG
High temporal resolution Noninvasive low cost
26
Disadvantages of EEG
Low spatial awareness only records signals from the surface correlation
27
Advantages of MEG
High temporal resolution Noninvasive
28
Disadvantages of MEG
Low spatial resolution costly correlation
29
LOC: Lateral occipital complex
Visual object detecting and processing
30
FFA: Fusiform face area
Face information visual processing
31
Different study types for FMRI
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)
32
FMRI VS MRI
MRI = Brain Anatomy FMRI = Brain functions
33
Criteria of magnetic fields
Uniformity Strength
34
3 components of a scanner
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
35
what happens when a proton spins?
when the proton spins, it will create a magnetic field bc it has a charge
36
Angular momentum
a quantity given by multiplying the mass of a spinning body by its angular velocity
37
Magnetic moment
The torque exerted on a magnet or a moving electrical charge when placed in a magnetic field
38
Do all nuclei exhibit NMR Effects?
NMR effects require both magnetic moment and angular moment ( at the same time) - Only odd numbered atomic mass has magnetic moment
39
Pauli Exclusion principle
odd numbered atoms are more unstable
40
Parallel vs antiparallel alignment
Parallel state-> alpha spin state (lower energy) more stable Antiparallel state-> beta spin state (higher energy) more unstable
41
Zeeman Effect
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
Net magnetization
Is the difference between the number of spins in the parallel and the antiparallel state (also called bulk magnetization)
43
What are the two planes that can be used to measure net magnetization
Longitudinal and Transverse
44
precession
Changing in the orientation of the rotational axis of a rotating body
45
What is the longitudinal plane = to?
Antiparallel state
46
What is the transverse plane = to?
Parallel state
47
T1
Measures how quickly the protons realign with the main magnetic field
48
T2
Measures how quickly the proton gives off energy as they recover to equilibrium
49
T1 Images
characteristics: fat = bright water = dark Sensitive to: Anatomical details btw gray and white matter) helpful in detecting vascular change
50
T2 IMAGES
Characteristics: fat = dark water = bright blood flow = dark lesion = white sensitive to: anatomical details (csf spaces/ventricles) lesions (except near csf)
51
T2 FLAIR IMAGE
FLAIR: Fluid attenuation inversion recovery characteristics: csf = dark nonfree flowing fluid = bright Sensitive to: lesions near csf/ventricles edema (swelling)
52
Repetition time
Interval between successive excitation pulses - TR is always greater than TE
53
Echo time
Interval between excitation and data acquisition
54
can MRI Machines detect both t1 and t2?
No, it can only detect T2 decay and t1 must be derived
55
Larmor equation
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
Slice Excitation
Cn be used to differentiate location of precessions By varying the magnetic and excitation frequency, we can selectively limit the NMR.
57
What are the five steps to slice selection/excitation
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
what do we use frequnecy and phase for?
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
what can be treated with motion correction?
1. Head motion leads to fake activation (most noticeable at edges) 2.) Regions of interest shift over time
60
what cannot be treated with motion correction?
Signal distortions due to motion of head
61
issue with motion correction algorithms?
Can introduce artifacts that weren't there originally
62
When should you test more participants?
When studying clinical populations when data loss is likely behavior correlations
63
what are the hidden costs of underpowered studies?
* Likelihood of false positives * researchers time trying to make sense of marginal effects * delays during review process
64
what do we use subtraction logic for?
To isolate some specific cognitive functions that we are interested in.
65
Mental chronometry
Uses reaction times to infer cognitive processes
66
How do we control the mental operations that subjects carry out in the scanner?
1. Manipulate the stimulus ( for automatic mental processes) 2. Manipulate the task (for controlled processes)
67
what are the three different types of confounds?
attentional motor eye movement
68
Dorsal attention network
helps orient attention in a goal-directed manner
69
Ventral attention network
detects stimuli and triggers reorientation to them
70
How to deal with attentional confounds:
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
How to deal with motor confounds:
GOAL: Have equal number of responses across all conditions have motor responses unrelated to task at hand
72
How to deal with eye movement confounds:
1. require participants to maintain fixation throughout the experiment 2. let participants free view but record, quantify and compare eye movements across conditions
73
when are errors in HRF models most problematic?
In the undershoot phase
74
what happens if the model HRF doesn't fit the data well?
Our estimated activation will not be estimated well and our residuals will be higher
75
what are the problems and solutions of repeating sequence block design?
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
what are the problems with random sequencing:
1. Randomization can be flukey 2. spend a lot of time defining protocols for analysis to have different randomizations
77
Pros and cons of Regular baseline block design
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
Slow event related design pros and cons
Pros: useful for designs with motion artifacts (grasping, swalling) analysis is easier to isolate cons: low statistical power subjects get bored
79
Block design
Have good detection and poor estimation
80
Slow event related designs
Good estimation but poor detection
81
why should we jitter>
yields larger fluctuations in signal
82
How do we jitter?
Include 1-2 null trials between real trials
83
sequence
for n # of conditions there are n^2 ways that the conditions could follow each other
84
when can you not counterbalance?
when subject errors mess up counterbalancing, decision making where someone chooses choice 1 or 2, correlations with behavior, and memory experiments
85
Pros and cons to Rapid ER Design
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
what condition shows the clearest data?
Higher effect with lower noise
87
what does R^2 tell us (the correlation)
Tells you how much noise is in the data and how well the correlation between the predictive model and the raw signal
88
what is a type 2 error?
Incorrect rejection: occurs when there is a real activation difference in a given voxel but the statistical test does not indicate activation
89
What is a type 1 error?
False positive: no real activation difference but statistical test indicates there is
90
Issue with Bonferroni correction:
Assumes each voxel is independent of others which is not true
91
Step by step of cluster correction:
1. choose cluster defining threshold 2. estimate smoothness of maps 3. run monte carlo stimulations 4. set a minimum cluster size (k)
92
How to use GLM for FMRI DATA
Adjust the height of the predictor(slope) and the constant (intercept) to best fit the data
93
what does the slope determine?
Whether the manipulation is good
94
what is a beta weight?
Size of difference
95
Talairach coordinate system:
Based on alcoholic old lady, any brain can be squished or stretched to fit hers
96
What is the first step to normalizing the brain into the system?
Rotate the brain into the anterior and posterior commissure and make sure both are aligned
97
what are x, y, z
X = LEFT/RIGHT Y=ANTERIOR/POSTERIOR Z=SUPERIOR/INFERIOR
98
mni space
Based on many subjects, using nonlinear warping for transformations
99
Which space provides brodmanns area?
Only tal
100
steps for cortical flattening:
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

Cognitive NeuroImaging (1 decks)

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