Hoofdstuk 4

Question 1

One key difference between structural imaging methods and functional imaging methods

Answer 1

• structural imaging is based on the fact that different types of tissue (skull, greymatter, whitematter, cerebrospinal fluid) have different physical properties
• these properties can be used to construct detailed static maps of the physical structure of the brain
• CT= Computerized Tomography
• MRI = Magnetic Resonance Imaging

Question 2

Functional Imaging is based on the assumption that

Answer 2

neural activity produces local physiological changes in that region of the brain
- produce dynamic maps of the moment-to-moment activity of the brain, when engaged in cognitive tasks

Question 3

Structural Imaging

Answer 3

measures of the spatial configuration of different types of tissue (CT/MRI)

Question 4

Functional Imaging

Answer 4

measures temporary changes in brain physiology associated with cognitive processing (fMRI - based on a hemodynamic measure)

Question 5

CT = Computerized Tomography

Answer 5

constructed according to the amount of x-ray absorption in different types of tissue

• amount of absorption is related to tissue density

Question 6

MRI

Answer 6

better spatial resolution, which allows the folds of individual gyri to be discerned
- beter onderscheid white/grey matter
- adapted for use in detecting the changes in blood oxygenation (associated with neural activity) “functional MRI”

Question 7

Strength of magnetic field is measured in Tesla

Answer 7

gemiddelde scanner 1,5T - 3 T, maar bestaat ook 7T

Question 8

T1 relaxation time

Answer 8

variations in the rate at which the protons return back to the aligned state following the radio frequency pulse = can be used to distinguish between different types of tissue

Question 9

PET (Position Emission Tomography)

Answer 9

measure bloodflow to a region directly
- need administration of radioactive tracer

Question 10

PET/fMRI/fNIRS

Answer 10

hemodynamic methods

Question 11

VBM

Answer 11

Voxel Based Morphometry
- voxel = volume-based unit (pixel = 2D)

Spatial Resolution fMRI (1mm depending on the size of the voxel)

Question 12

DTI

Answer 12

Diffusion Tensor Imaging

Question 13

Fractional Anistropy

Answer 13

FA
- a measure of the extent to which diffusion takes place in some directions more than others

Question 14

The component of the MRsignal that is used in fMRI

Answer 14

is sensitive to the amount of deoxyhemoglobin in the blood

Question 15

BOLD

Answer 15

Blood-Oxygen Level-Dependent Contrast
- the way that the BOLD signal evolves over time in response to an increase in neural activity (Hemodynamic Response Function HRF)

1) initial Dip
2) Overcompensation
3) Undershoot

fNIRS measures the bold signal by sending “light”of a particular wavelength to the brain (near infrared)
- more portable and tolerant of movement
- shallow neural activity

Question 16

Cognitive subtraction

Answer 16

experimental design in functional imaging in which activity in a control task is subtracted from activity in an experimental task

Question 17

Pure Insertion/Pure Deletion

Answer 17

the assumption that adding a different component to a task does not change the operation of other components = main problem with cognitive subtraction

Question 18

the method of cognitive conjunction

Answer 18

requires that one is able to identify a set of tasks that have a particular component in common

Question 19

Efference Copy

Answer 19

a motor signal used to predict sensory consequences of an action (perceptual system knows what to expect)

Question 20

The main difference between a parametric design and a categorical design

Answer 20

is that in a parametric design, the variable of interest is treated as a continuous dimension rather than a categorical distinction
- one is measuring ASSOCIATIONS between brain activity and changes in the variable of interest, rather than
- measuring DIFFERENCES in brain activity between 2 or more conditions
(one is likely to use correlations to analyze data collected using a parametric design)

Question 21

Functional Integration

Answer 21

the way in which different regions communicate with each other
- measuring functional integration: resting state paradigms (finding networks in a rested state

Question 22

Default Mode Network

Answer 22

a set of brain regions that is more hemodynamically active during rest than during tasks

Question 23

Central Problem in the analysis of functional imaging data

Answer 23

is how to deal with individual differences
- location of sulci can differ by a centimeter or more
- stereotactic normalization: mapping of individual differences in brain anatomy onto a standard template, followed by smoothing

Smoothing = redistributing brain activity from neighbouring voxel to enhance the signal-to-noise ratio

Question 24

False Discovery Rate

Answer 24

generate thousands of random brain images (e.g. permuting the data) and select a threshold (p>0.05) based on random data sets

Question 25

Family Wise Error (FWE)

Answer 25

correcting many statistical comparisons based on the number of tests being conducted

Question 26

Functional Imaging signals are assumed to be correlated with the metabloic activity of neurons, and synapses in particular

Answer 26

neurons can be metabolically active by inhibitory interactions (when the presynaptic neurons are active, postsynaptic switched off), or by excitatory interactions (preynaptic off, postsynaptic on)

Question 27

Activation and deactgivation

Answer 27

Asimply refer to the sign (positive or negative of the difference in signal between 2 conditions)

Question 28

Semantic Dementia

Answer 28

Functional Lesion primarily in the semantic memory system that stores the meaning of words and objects

Question 29

Multi-Voxel Pattern Analysis (MVPA)

Answer 29

examine the pattern of activation over a distributed set of voxels to enable a more fine grained approach