Lecture 10 - Neuroimaging and Map Plasticity in Humans Flashcards
1
Q
What is diagnostic neuroimaging?
A
- X-ray
- 3D image & good bone contrast
- Uses radiation
2
Q
What is MRI
A
- Using magnetism
- Patient within large static magnet
- Smaller magnets change fields in different directions at right angles to one another
3
Q
Are all brain contrasts the same in MRI?
A
- No, diff contrasts provide diff info
- Used to build up fuller picture
- No one contrast is best for all injuries
- e.g static MRI = T1/T2/Proton density
4
Q
What is BOLD contrast (fMRI)
A
- Blood Oxygenation Level Dependent
- Brain cannot perform anaerobic respiration
- Can map what areas are working harder depending on how much blood travels there
- Increase local flow = Increased ratio between de/oxygenated blood = increased MR signal
5
Q
What is a voxhall?
A
- Volume element (3d location)
- Makes fMRI imaging
6
Q
What is the summary of MRI
A
- Brains contain high conc of hydrogen (in water)
- Protons will orientate magnetic fields when you put them in a bigger magnetic field
- Arrangement is disrupted when radio-frequency waves are applied
- As protons go back to normal magnetic field, they emit signal that is detected by MR scanner
7
Q
What does the difference in magnetic properties between de/oxygenated blood signify?
A
- Special MR contrast holds info of ratios of blood
- BOLD can be used to track what neurons consume more blood & therefore involved in certain tasks
8
Q
What is the problem with vascular imaging?
A
- Inferring that relationship is using up energy is static = measuring what the neurons need to work
9
Q
What is MEG?
A
- Current generated by single neuron is too weak to be detected
- MEG detects a change in overall magnetic field caused by lot of neurons working together
- Cannot go deep into the brain
- Has to be kept in a sep room to avoid disruptions and needs to have a tank for hydrogen = expensive
10
Q
What was a brief history of vibration?
A
- Stimulator that would go up and down its in a magnetic field
- Claw = tubing = cannot go fast
- Turning electrical signal into vibrations to study touch
11
Q
What is the cutaneous rabbit illusion?
A
- 3 diff vibrotactile stimulators on arms
- Filling in when people tap you = dissociates subjective experience with objective stimulation
- Mapped areas in somatosensory cortex and ran the sequence of taps. One condition was that they would feel the tap in the middle because they had a tap, second condition was the feeling of jumping between taps
- Area mapped was not getting stimulation, there was activation in brain = not reflecting objective reality
12
Q
How did they investigate spatial resolution?
A
- (How fine can you differentiate between textures)
- Present domes to fingers and ppts have to work out orientation
- Very hard to get both calipers on (have to put domes on with calipers) at the same time so person also measure time
13
Q
How did they try to get over the temporal resolution with the domes?
A
- Pet scan contrasting how fine gaps are and orientation of dome
- Found no diff activity in somatosensory areas
- Significant blob between parietal/occiptal lobe that was prev active in visual discrimination of gratings
14
Q
How do we know the blob is doing the job?
A
- Using TMS
- Experiment design: delivered a disruptive pulse to area located in ppts when they did different tactile tasks
- Dropped domes onto fingertip, send signal to TMS coil to fire at given delay (clear temporal resolution)
- Ppts either had to work out if something was there (control)/ orientation/ pure spatial discrimination
15
Q
What were the TMS results?
A
- Middle and left electrodes were closest to blob and showed temporal & spatial specificity.
- Blasting there would disrupt orientation task only after a specific time
- Non-classical areas in somatosensory discrimination that involves visual imagery components
