Lecture 7, 8, & 9 - Interference, MRI, EEG Flashcards
What does the Visual network do? Where is it located?
Determines what an objet is
- occipital lobe processes visual info
- inferior temporal lobe determine what an object is
What is in the somatomotor network?
M1 and S1
What does the dorsal attention network do? Describe where the segments of it are
Determines whether an object is moving, where it is in space, and guides eye movement to the object
- just anterior and posterior to somatomotor and just anterior to the visual network
What does the ventral attention/salience network do? Where is it anatomically?
Important for monitoring environment broadly and detecting unexpected stimuli and shifting attention
- ventral anterior and posterior of somatomoto
What does the limbic network do? Where is it anatomically?
- orbitofrontal cortex regulates emotion
- entorhinal cortex regulates memory
Most anterior and ventral area of brain
What does the control network do? Where is it anatomically?
Important for complex cognition, making decisions, solving problems, holding information in mind, and representing numbers
- weird to describe, a bit anterior but less so than the default mode network and it random bits around posterior brain
Where is the default mode network? What does it do?
- Areas are suppressed while doing things. Responsible for internally-directed thought, thinking about things not in the current environment, the past, the future, the minds of other people
- Anterior to the brain but also largely in temporal lobes, sagital cut shows it takes up a large portion of the cortex
What happened to Louis Victor Leborgne that caused him to only be able to say “tan”?
Lesion to his Broca’s area, understood speech but couldnt speak anything besides tan
What happened to Henry Molaison when his hippocampus was removed?
Never remembered anything again
Why does damage to white matter make it hard to interpret lesion studies?
You dont know whether the input or output caused the problem or just the severing of the connection itself
Do patients with aphasia that have issues with production deficits and comprehension deficits usually have lesions in the same place?
No
How does brain stimulation work?
Electrodes are inserted into the brain to cause or stop neuronal firing
How does optogenetics work?
- insert gene into virus that contains an opsin and promoter for that opsin
- insert virus into part of rats brain
- attach electrode and a cable into area of brain
- activate laser light
- either causes inhibition or excitation
Is TMS precise?
Not really
What does TMS stand for?
Transcranial magnetic stimulation
What can TMS do?
Quiet brain areas that are too active, good for depression, migraines, OCD, and smoking cesssation
What are the pros and cons of TMS?
Pros:
- temporary
- reasonably focal
- can be randomly assigned
Cons:
- some areas cannot be stimulated cus theyre too deep
- uncertainty over the size of each stimulation area
- may be affecting an excitatory or inhibitory area
How does an MRI work?
- adds a static magnetic field to the brain
- orients protons in a certain direction
- RF pulse thats orthogonal to static magnetic field reorientates protons
- relaxation is measured
What’s the step by step for an MRI?
- protons align with a strong static magnetic field
- radiofrequency pulse is applied to excite protons and make them spin together
- RF pulse is turned off and protons relax
- coils detect the energy released during relaxation
What’s the difference between T1 and T2?
They measure the rate of relaxation of protons but they vary by tissue
Where is T1 highest? Where is T2 highest?
T1: White matter
T2: CSF
What can a structural MRI show?
- Volume of subcortical structures
- cortical thickness & area
- figuring out anatomical divisions
What does a Diffusion Tensor Imaging do?
- fractional anisotropy aka diffusion of water in one direction compared to 2 orthogonal directions
- basically looks at connections within the brain
What does a task-based functional MRI do?
Sees what areas of a brain activate the most when you perform an activity
How does an fMRI work?
- deoxygenated hemoglobin has greater magnetic susceptibility and causes faster decay of T2 signal
- more oxygenated hemoglobin -> higher MR signal
- more deox hemoglobin -> lower MR signal
What causes dilation of blood vessels in the brain during an activity?
Astrocytes
Does lower neural activity lead to a higher or lower MR signal?
Lower, theres less oxygenated blood there
Does higher neural activity lead to a higher or lower MR signal?
Higher, theres more oxygenated blood
What does BOLD stand for?
Blood oxygen level dependent signal
Would a BOLD signal increase or decrease in an area of interest when an activity is done that uses that area?
Increase, it looks like a bar graph
What does whole brain analysis do?
Registers a common space which is taken from an average across participants
What happens to a BOLD signal during a resting state fMRI?
It fluctuates but anatomically connected areas show correlated BOLD fluctuations
What was rsfMRIs used to figure out?
The different neural networks
Done with seeds which are time courses that are extracted from regions and correlated with other voxels
Coding by spike rate: how is it done?
Insert an electrode in brain area of interest and record action potentials, if its involved a lot it’ll have a lot of APs, if baseline its not involved at all, if its quiet of APs then the area is suppressed by the task
What is a local field potential?
Detection of Synchronous dendritic activity
How can raster plots and histograms display spike rate data?
Do a ton of trials which shows the frequency of spikes when a stimulus is present and then some where it isn’t, wherever you see Hz increase is where the brain is being activated
How would you map a receptive field of a V1 neuron?
Have someone look at a fixation point, and see which cells respond when a stimulus is put over the receptive field (some area outside the fixation point)
Do cells in the motor cortex care about which direction a body part is moving?
Yes, some respond more to wanting to move left right, up or down
What is Electrocorticography?
A technique that measures brain waves from electrodes place on the surface of the brain
What’s a weird finding that was found with ECog? Think Batman
Cat woman specific cells
What is an EEG?
Electroencephalography
What do EEGs measure?
Post dendritic current?
What is an EOG? What is an ERP?
EOG: Electrooculogram
ERP: Event related potentials
Pros and cons of EEG?
Pros:
- fast
- non invasive
Cons:
- poor spatial resolution
What can EEG be used to detect?
Epilepsy
What is an ERP?
Basically hundreds of combined trials of EEGs that remove background noise
