Lecture 7: Intro to the use of brain imaging for pain (Dr. Etienne Vachon-Presseau

Question 1

When were the first MRI images done and by who were they invented?

Answer 1

Raymond Damadian in 1977

Question 2

How did the first MRI images work?

Answer 2

• electromagnetic field interacts with coil around the torso of the subject
• didn’t work caus subject was too fat

Question 3

Who made the MRI images work for the first time and how?

Answer 3

• Larry Minkoff 1977

- Used a skinnier subject

Question 4

What type of MRI machine is widely used today in hospitals?

Answer 4

Siemens 3 Tesla

Question 5

What is a tesla in medical terms?

Answer 5

strength of the magnetic field

Question 6

What strength of Tesla do we use today in hospitals?

Answer 6

1.5 tesla

Question 7

What strength of Tesla do we use today for research?

Answer 7

3 tesla

Question 8

How is expensive is it to get the whole MRI system setup?

Answer 8

• 3 million

- Not just the machine, requires a lot of surrounding infrastructure

Question 9

What is BOLD response?

Answer 9

The amount of oxygen used by the brain

Question 10

How big are the changes in bold response to a heat stimulus? (generally)

Answer 10

-pretty small: 2.5 %

Question 11

How can we characterize this way of imaging ?

Answer 11

• very indirect way of measuring neuron oxygen consumption

- through normal hemodynamic response

Question 12

When was the first brain imaging study of pain?

Answer 12

1991

Question 13

What type of imaging did they use for the first brain imaging study of pain?

Answer 13

They used a pet scan because MRI was not good enough yet

Question 14

How could they infer pain processing through PET scans?

Answer 14

• The PET scans suggested where the pain was processed
• These regions weren’t necessarily dedicated to pain.
• Inferred that pain is distributed around the brain, not localised in a single spot

Question 15

Are there differences in the brains of people who rate pain at different intensity?

Answer 15

• less brain activity in people who report less pain
• people who are more sensitive a different brain response
• However, these results were not replicated

Question 16

What does the software neurosynth.org do?

Answer 16

Generates maps from many MRI studies

Question 17

How can we construct models for pain using brain imaging?

Answer 17

• Distributed representation of pain
• Regions are involved in the multidimensionality of pain
• Suggested circuitry of pain

Question 18

What is a downside of these modelled circuitry of pain?

Answer 18

It is very hard to infer directionality

Question 19

What is pain correlated with?

Answer 19

• pain correlated with threat perception

- eg: relaxing music, pleasant images will affect pain perception

Question 20

How are intensity and unpleasantness modulated ?

Answer 20

-modulated independently though very closely coupled

Question 21

What is a voxel?

Answer 21

• A three dimensional pixel of the brain

- 1 to 3 mm square depending on resolution

Question 22

How do we work with voxels?

Answer 22

• Tryna work backwards from voxels to the image that caused it
• Infer stimulus from the voxel pattern

Question 23

What did we try to decode from voxel input?

Answer 23

-tryna teach a program to recognize reams from voxel input

Question 24

What relationship was found between fibromyalgia and pain processing?

Answer 24

Control has less expression of the pain pattern than fibromyalgics at the same mechanical pressure

Question 25

What aspect of pain does the prefrontal cortex control?

Answer 25

goal context and expectancy

Question 26

What regions of the theoretical model of the neurobiology of placebo do not respond to pain?

Answer 26

Regions in red, see slide

Question 27

What regions of the theoretical model of the neurobiology of placebo respond to pain?

Answer 27

Regions in blue see slide

Question 28

What mechanism does placebo rely on?

Answer 28

Descending inhibition, can be blocked by naloxone