Resting state MRI

Question 1

What two types of connectivity can we measure with fMRI resting state?

Answer 1

Structural connectivity - white matter fibres (axonal) with diffusion-weighted MRI and wiring of the brain
Functional connectivity - Temporal correlations between regions. Network of regions responding to a task. fMRI

Question 2

What are the 4 characteristics of a network?

Answer 2

Directed/Undirected edges
Binary/Weighted edges

Question 3

How are each of the connectivity networks characterised

Answer 3

Structural - Directed binary
Functional - Undirected weighted
Effective - Directed weighted

Question 4

What statistics technique is used to see how much of a signal resembles that task?

Answer 4

Linear regression

Question 5

What two techniques are used to functional connectivity analysis?

Answer 5

1. Seed voxel analysis
2. Independent Component analysis - decomposition of the data into components

Question 6

What is seed voxel analysis?

Answer 6

You pick a region and take a signal from that region and then you do a linear regression to see what other regions of the brain correlate with the region you picked

Question 7

What is Independent Component Analysis

Answer 7

Instead of picking a region in seed voxel you just do a whole brain analysis and gives you the strongest correlations

Question 8

What are the pros of analysing functional connectivity?

Answer 8

• Useful when there is no experimental control over the system of interest and no model of what caused the data e.g sleep, hallucinations, resting state activity
• Not confounded by performance differences from ptps e.g dementia

Question 9

What are the cons of analysing functional connectivity?

Answer 9

• Interpretation of results is difficult = less control over ongoing activity
• Don’t have an mechanistic insight
• Less powerful

Question 10

What percentage of fMRI studies involve resting state?

Answer 10

25%

Question 11

What are the results from resting state fMRI as demonstrated by Beckmann et al (2005)

Answer 11

Activity in the primary and secondary visual cortex
Default mode network
Central motor networks
attention/monitoring network = Frontoparietal

Question 12

What areas are involved in the default mode network? What affects it?

Answer 12

mediofrontal cortex, posterocingulate cortex, hippocampal areas, thalamus and parietal lobes
- Alzheimer’s, aging, addiction, ADHD, diabetes and a lot more

Question 13

What happened to the default mode network in people with Alzheimer’s?

Answer 13

IT changed, some areas had less activity

Question 14

What conclusions can be made about the default mode network?

Answer 14

Its not very specific = specificity in changes in neurological or psychiatric conditions is low
It is interesting as it is involved in everything
Related to the function of the attentional orientation, internal monitoring areas

Question 15

How was the default mode network first identified?

Answer 15

During a demanding task - N-back
Found to be a negative BOLD signal so the DMN is more active during rest
PET scan

Question 16

What does the DMN tell us

Answer 16

Activity persist even in the absence of explicit external stimuli/task