Lecture 7: Intro to the use of brain imaging for pain (Dr. Etienne Vachon-Presseau Flashcards
When were the first MRI images done and by who were they invented?
Raymond Damadian in 1977
How did the first MRI images work?
- electromagnetic field interacts with coil around the torso of the subject
- didn’t work caus subject was too fat
Who made the MRI images work for the first time and how?
- Larry Minkoff 1977
- Used a skinnier subject
What type of MRI machine is widely used today in hospitals?
Siemens 3 Tesla
What is a tesla in medical terms?
strength of the magnetic field
What strength of Tesla do we use today in hospitals?
1.5 tesla
What strength of Tesla do we use today for research?
3 tesla
How is expensive is it to get the whole MRI system setup?
- 3 million
- Not just the machine, requires a lot of surrounding infrastructure
What is BOLD response?
The amount of oxygen used by the brain
How big are the changes in bold response to a heat stimulus? (generally)
-pretty small: 2.5 %
How can we characterize this way of imaging ?
- very indirect way of measuring neuron oxygen consumption
- through normal hemodynamic response
When was the first brain imaging study of pain?
1991
What type of imaging did they use for the first brain imaging study of pain?
They used a pet scan because MRI was not good enough yet
How could they infer pain processing through PET scans?
- 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
Are there differences in the brains of people who rate pain at different intensity?
- less brain activity in people who report less pain
- people who are more sensitive a different brain response
- However, these results were not replicated
What does the software neurosynth.org do?
Generates maps from many MRI studies
How can we construct models for pain using brain imaging?
- Distributed representation of pain
- Regions are involved in the multidimensionality of pain
- Suggested circuitry of pain
What is a downside of these modelled circuitry of pain?
It is very hard to infer directionality
What is pain correlated with?
- pain correlated with threat perception
- eg: relaxing music, pleasant images will affect pain perception
How are intensity and unpleasantness modulated ?
-modulated independently though very closely coupled
What is a voxel?
- A three dimensional pixel of the brain
- 1 to 3 mm square depending on resolution
How do we work with voxels?
- Tryna work backwards from voxels to the image that caused it
- Infer stimulus from the voxel pattern
What did we try to decode from voxel input?
-tryna teach a program to recognize reams from voxel input
What relationship was found between fibromyalgia and pain processing?
Control has less expression of the pain pattern than fibromyalgics at the same mechanical pressure
What aspect of pain does the prefrontal cortex control?
goal context and expectancy
What regions of the theoretical model of the neurobiology of placebo do not respond to pain?
Regions in red, see slide
What regions of the theoretical model of the neurobiology of placebo respond to pain?
Regions in blue see slide
What mechanism does placebo rely on?
Descending inhibition, can be blocked by naloxone
