Chap. 2 Week 2-3 Flashcards
How do we learn about neuroanatomy? (5)
Assess behaviour
Studying the effects of brain damage
Perturbation of neural function
Assessing brain structure
Assessing brain function
What is double dissociation?
When two related mental processes are shown to function independently of one another.
What are examples of perturbing neural function?
DBS (invasive) - drill hole in skull, place electrode, stimulate with shock to induce firing of neurons.
CONS:
1. too invasive to use on a large portion of the brain
2. Different frequencies and amplitudes are needed for each patient
What are all of the perturbing of neural function examples?
DBS
TMS
tDSC
tACS
What is a TMS?
Trans-cranial magnetic stimulation
- magnetic coils induce electrical current over brain surface
Used to knock out or interfere with function
What is tDCS? Invasive or non invasive?
Transcranial direct current stimulation. Non invasive
Uses a low, constant current via electrodes placed on the scalp.
Anode = excitable
Cathode = less likely to fire
PRO : can selectively excite or inhibit targeted neural areas depending on the polarity of the current.
CON: poor spatial resolution & effects are short lived (1 hour)
What is tACS? Invasive or non invasive? What are the pros and cons?
Transcranial alternating current stimulation.
Electrical currents oscillate to stimulate the brain. Oscillations at specific frequencies evidenced to be linked to cognitive processes.
How do we study brain structure?
Golgi stain - stains neurons, dendrites and axons sometimes
Nissl stain- cell bodies only
Myelin- axons
What is retrograde degeneration?
Degeneration of nerve cell between damage and cell body (back to the cell body)
What is anterograde/ wallerian degeneration?
Degeneration of nerve cell between the damage and end process (away)
What is an example of brain connectivity?
Cerebellum is known to be involved in non-motor task such as language and memory which are involved in the frontal cortex. Therefore, the CB has anatomical connections with the frontal lobe.
What is a CT?
Computerized tomography. Uses x-rays to get a 3D image of the brain.
Good for the visualization of large lesions that include cell loss (stroke), increases in fluid (hemorhage) or changes in density (tumour)
MRI. How does it work?
Uses a strong magnetic field 1.5 Tesla to image the brain. Magnet aligns the protons in the same direction.
What is registration?
The average of all brain images into 1.
What are the types of sMRI used?
T1w imaging —> most used for gross anatomical structure
AND
Diffusion MRI (dMRI) —> to look at anatomical connectivity
Why is it important to understand WM structure to understand brain function and cognition?
Because more or less myelin relates to different speed of function.
AKA local differences in axons is important for signal transmission
How is dMRI measured?
Measures the movement of water molecules parallel to the fiber direction. —> MRI can measure this movement (diffusion coefficient) in different directions
How are neuroanatomy and dMRI connected?
dMRI provides an index of WM.
Fractional anisotropy—> directionality of diffusion—> value of 0 meaning there is isotropic diffusion (unrestricted in all areas) or 1.
What is an EcoG?
Electrocorticography
Electrode net applied to cortical surface
FMRI is dependent on…?
The hemodynamic signal
Measures CHANGES/DIFFERENCES but we do not know the specific mechanism
Explain connectivity mapping
Regions = nodes
Connections = edges —> the strength of connection between nodes
How do we measure connectivity mapping for structural?
DMRI WM connectivity
SMRI “structural covariance” analyses
How do we measure connectivity mapping for functional?
FMRI
EEG
MEG
—- Nodes, correlation (r) between as edges
BOLD
What is specific about HS, HG, and STG?
The more you move away from this area, the less sensitive you are to frequency but more specific for words.
