Lecture 11 - Neuroimaging & Map Plasticity in Humans Flashcards
(35 cards)
What did the 1978 study on static maps in adult monkeys show about areas 3b and 1?
It demonstrated two mirrored topographic representations of the body surface in areas 3b and 1, revealing fine detial of somatosensory maps in adult monkeys
What was the key finding of Merzenich et al., 1984 (digit amputation in owl monkeys)?
The receptive fields (RFs) of the amputated digit became responsive to adjacent digits, showing adult cortical plasticity without creating a ‘silent’ zone
What change did Clark et al., 1988 observe after experimental syndactyly (webbed/fused fingers)
Surgically joining two digits increased coincident input, leading to merged receptive fields and altered somatosensory map structure at the digit borders
Year of mirrored maps in 3b/1 areas?
1978
Year od digit amputation study showing adult plasticity?
1984
Year of syndactyly-induced plasticity?
1988
What is a limitation of CT scans in research use?
CT scans use radiation, limiting its suitability for longitudinal/follow-up studies
How does MRI work structurally?
- It uses magnetism
- A static magnetic field aligns hydrogen protons, and RF pulses disrupt alignment
- As protons return to equilibrium, they emit detectable signals
What are MRI contrast types and why are they important?
- T1, T2, and Proton Density contrasts provide varied structural details
- No single contrast is optimal for all types of injury
What is BOLD contrast in fMRI?
- It tracks oxygenated vs. deoxygenated blood ratios
- Neuronal activity increases blood flow, changing MR signals, which are used to infer regional brain activity
What classic fMRI design was used to study visual cortex activation?
A blocked design with alternating ON/OFF periods of a flickering checkerboard stimulus (Kwong et al., 1992)
fMRI uses what signal?
BOLD (Blood-Oxygen-Level Dependent)
Brain % body weight vs glucose use?
2% weight, 25% glucose
What does Magnetoencephalography (MEG) measure, and what are its strengths?
- MEG detects magnetic fields from synchronous firing of pyramidal neurons
- Magnetic fields pass transparently through the skull, making MEG less affected by conductivity differences
How strong must a source be for MEG to detect it?
Roughly 40mm^2 of synchronously firing cortex is needed to produce a measurable signal (Hamalainen & Hare, 2002)
Which brain areas are best accessed by MEG?
MEG is most sensitive to tangential sources (e.g., in sulci), particularly in superficial cortical areas
Can MEG detect single neuron activity?
No
Minimum source size for MEG signal?
40mm^2
MEG strength? Weakness?
- High temporal resolution
- Low spatial resolution
What is somatotopy?
The spatial mapping of body parts onto corresponding brain regions in the somatosensory cortex (e.g., S1)
What illusion was used to test subjective vs. objective somatosensory experience? What did research show?
The Cutaneous Rabbit Illusion (Blankenburg et al., 2006) showed subjective perception can activate S1 even without direct stimulation
What tool assesses tactile spatial resolution in research>
JVP domes - used similarly to grating discrimination in vision
What did Van Boven et al. (1994) show about JBP domes?
They provide reliable measures of tactile resolution and are less prone to bias than 2-point discrimination
What does 2-point discrimination mean?
The ability to distinguish between two distinct points of touch on the skin, even when they are close together
