fMRI ARTICLES (mini-quiz 6)

Question 1

What does fMRI stand for, and what does it measure?

Answer 1

Functional Magnetic Resonance Imaging; it measures changes in blood oxygen levels to infer neural activity.

Question 2

What is the BOLD signal in fMRI, and what does it represent?

Answer 2

Blood Oxygen-Level Dependent signal; it reflects the changes in oxygenated and deoxygenated hemoglobin in the blood, indicating neural activity.

Question 3

What are the two most common experimental designs used in fMRI studies?

Answer 3

Block designs and event-related designs.

Question 4

How does the General Linear Model (GLM) help in analyzing fMRI data?

Answer 4

It correlates predicted neural responses with observed activity to identify task-related brain regions.

Question 5

What is the importance of pre-processing in fMRI data analysis?

Answer 5

It corrects for artifacts, aligns data, and prepares it for further analysis, ensuring accuracy in results.

Question 6

Explain the concept of voxel in the context of fMRI.

Answer 6

A voxel is a 3D pixel representing a volume element in the brain, with spatial resolution determined by voxel size.

Question 7

What is the purpose of the ‘field map’ in fMRI sessions?

Answer 7

To measure the homogeneity of the magnetic field and correct distortions during data analysis.

Question 8

What is a rapid event-related design, and what are its advantages?

Answer 8

An fMRI experimental design with shorter delays between trials, allowing for more efficient data collection.

Question 9

What is spatial smoothing in fMRI, and why is it applied?

Answer 9

It’s a technique that averages data from neighboring voxels to reduce noise and enhance signal clarity.

Question 10

What role does the hemodynamic response function (HRF) play in fMRI data interpretation?

Answer 10

It models the time course of the BOLD response to neural activation, crucial for data analysis.

Question 11

Why is high temporal resolution not achievable in fMRI?

Answer 11

Due to the sluggish nature of the BOLD response, which lags behind actual neural activity.

Question 12

What are some limitations of fMRI as a research tool?

Answer 12

Poor temporal resolution, indirect measurement of neural activity, and potential susceptibility to artifacts.

Question 13

How does a block design differ from an event-related design in fMRI studies?

Answer 13

Block designs involve continuous tasks during blocks of time, while event-related designs have discrete trials with random timing.

Question 14

What is meant by jittering in an event-related fMRI design?

Answer 14

Introducing random delays between stimulus presentations to ensure accurate statistical analysis.

Question 15

Explain the difference between structural and functional MRI.

Answer 15

Structural MRI provides detailed images of anatomical structures, while functional MRI captures brain activity over time.

Question 16

What is functional connectivity analysis in fMRI?

Answer 16

It identifies networks of brain regions that activate together, suggesting they are part of the same functional system.

Question 17

What factors determine the choice of voxel size in fMRI studies?

Answer 17

Desired spatial resolution and the trade-off with temporal resolution and data acquisition time.

Question 18

What are the advantages of using multivariate methods like Independent Component Analysis (ICA) in fMRI?

Answer 18

They can identify networks of event-related regions, offering insights into complex brain connectivity.

Question 19

What are the most widely used software packages for fMRI data analysis?

Answer 19

SPM (Statistical Parametric Mapping) and FSL (FMRIB Software Library).

Question 20

What is a free-running design in fMRI studies?

Answer 20

An experimental setup where events are presented continuously without structured breaks, like watching a movie.

Question 21

What is the main focus of the study in Neurophysiological Investigation of the Basis of the fMRI Signal?

Answer 21

Understanding the relationship between fMRI signals and underlying neural activity.

Question 22

What are Local Field Potentials (LFPs) and their significance in this context?

Answer 22

LFPs are low-frequency brain activity signals that correlate strongly with the BOLD response in fMRI.

Question 23

What does MUA stand for, and what does it measure?

Answer 23

Multi-Unit Activity; it measures the spiking activity of multiple neurons.

Question 24

How is the BOLD response related to LFPs according to the study?

Answer 24

The BOLD signal is more closely linked to LFPs, reflecting the input and local processing of an area.

Question 25

What is the primary difference between LFPs and MUA in their contribution to fMRI signals?

Answer 25

LFPs provide a more sustained and consistent correlation with the BOLD signal than MUA.

Question 26

How do haemodynamic changes reflect neural activity in fMRI?

Answer 26

Changes in blood flow and volume, detected by fMRI, are triggered by neural activity requiring more oxygen.

Question 27

What imaging technique is commonly used in these neurophysiological studies to measure the BOLD response?

Answer 27

Echo-planar imaging (EPI).

Question 28

Why are simultaneous intracortical recordings and fMRI crucial in these studies?

Answer 28

They allow for direct comparison between neural and haemodynamic responses, providing better understanding.

Question 29

What did the study find regarding the temporal dynamics of the BOLD response?

Answer 29

The BOLD signal lags behind neural activation by approximately 2 seconds and reaches a plateau after about 7 seconds.

Question 30

How does the spatial summation of LFPs and MUA differ?

Answer 30

LFPs integrate signals over a broader area (millimeters), while MUA is more localized (hundreds of microns).

Question 31

What techniques are used to reduce noise when recording neural signals during fMRI?

Answer 31

Special electrodes and interference compensation systems to minimize artifacts from the magnetic field.

Question 32

What role do visual stimuli play in neurophysiological experiments with fMRI?

Answer 32

They provide a controlled way to elicit and measure neural and haemodynamic responses.

Question 33

What conclusions were drawn about the fMRI signal in terms of neural processing?

Answer 33

It likely represents input and local processing rather than direct neural output.

Question 34

Why is the correlation between LFPs and BOLD responses higher than that with MUA?

Answer 34

LFPs capture more sustained neural activity, closely matching the slower BOLD signal.

Question 35

What challenges are associated with mapping neural activity using fMRI?

Answer 35

The underestimation of neural activity due to the low signal-to-noise ratio of haemodynamic responses.

Question 36

What impact does neural adaptation have on BOLD responses?

Answer 36

It can cause transient changes in neural signals, affecting the consistency of the BOLD response.

Question 37

What was the significance of using high-contrast stimuli in the experiments?

Answer 37

To investigate how changes in stimulus intensity affect both neural and BOLD responses.

Question 38

What methodological steps were taken to ensure the accuracy of neural signal recordings during fMRI?

Answer 38

Pre-whitening and filtering techniques to minimize correlations and enhance signal clarity.

Question 39

What is the implication of the study for interpreting human fMRI experiments?

Answer 39

BOLD activation may reflect not just spiking output but broader synaptic and local processing activities.

Question 40

Why is understanding the neurophysiological basis of fMRI signals important for neuroscience?

Answer 40

It provides deeper insights into how brain imaging results relate to actual brain function and structure.

Question 41

IN CLASS MINI-QUIZ QUESTION 1:

Question 42

IN CLASS MINI-QUIZ QUESTION 2: