10 Flashcards
(27 cards)
What is histology?
determination of structure and morphology of tissue
What do the Golgi, Nissl stains, myelin staining procedures show of the microscopic
structure of the brain?
golgi:
-1st to be discovered in staining
-stains dead cell bodies with silver chromate
nissl:
-violent stain, does not stain axons
-shows cell bodies
myelin:
-measures myelin of tissue
-shows where axons go
-increase detectability of target molecule
The Golgi stains show what neurons look like. The Nissl stains allow visibility inside the neuron. The myelin stains allow to see vsibility of axonal projections.
How do cranial X-rays work in general? What structures or damage show up how?
X-rays are shot through a person and onto a film and that produces a picture onto the film. White structures are high density and show the skull. Cranial x-rays show the skull and brain
What are the advantages and disadvantages of cranial X-rays?
advantages:
-picks up tumors, brain fractures, hemorrhages
-cheap, convenient, simple
Disadvantages: You can’t discriminate well between the brain tissue and the CSF. The regions of the brain are difficult to discern. Only 2 dimensional images, and it has poor structural resolution
radiation
Explain how angiography works and what it is used for.
-see where brain blood is used, vessels, and blockages
-process: an injected contrast material makes it easier to see where blood is moving and where blockages are (injects catheter via external artery to entry of arterial supply of blood)
-uses: detects aneurysms, tumors w/ new vasculature, vascular shifting due to lesion, and degeneration of brain tissue
-risk: uses radiation
What is the general process in computerized axial tomography, how is it different from an X-
ray? What disadvantage of X-rays goes for CT scans also?
A thin x-ray machine goes around the person and shoots thin “slices” of x-rays through the head and a computer makes up an image. The discrimination between brain structures is superior in CT scans when compared to x-rays Disadvantage: CT scans just like x-rays expose you to radiation and also require electricity
Which has the higher radiation dose: a skull X-ray or a head CT? why is that?
A typical skull X-ray has a dose of 0.1 while a CT scan has a dose of 2.0. CT scan is higher because it is sending out multiple x-rays in order to produce the image.
What is the BED and how can it be helpful?
The banana equivalent dose. Bananas are a natural source of radioactive isotopes. It is helpful in comparing bananas to how much radiation is in things.
How in general does an MRI work? What are the advantages of MRIs?
involves the application of a powerful magnetic field to image the brain
* magnetic field aligns axes of the natural spin or rotation of atoms in water molecules (esp. hydrogen atoms)
* Radiofrequency signal causes all aligned axes to spin like gyros
* Termination of radiofrequency signal causes nuclear atoms to return to original state, releasing electromagnetic energy in the process
* Released energy is measured and used to visualize the structure of the brain
Advantages: The advantages of an MRI are that it provides a detailed structure of the brain, no radiation, relatively cheap, available in hospitals, and they are good for research.
What types of things can be measured with MRIs, and how can it be used in research?
MRIs are used to measure differences in groups, grey matter volume, cortical thickness, cortical surface area, subcortical volume and shape. It can be used in research to compare structures of the brain amongst different groups.
–differnet from fMRI; MRI measures structure
Explain what DTIs can image, and in what types of disorders this is interesting information.
What descriptive research can be done with DTIs?
DTIs (Diffusion Tensor Imaging) is used to visualize and map the structure and connectivity of the brain’s white matter by tracking the movement of water molecules along neural pathways. This information is interesting in demyelinating disorders, such as MS, where white matter tracts are reduced.
Descriptive research that can be done with DTIs are changes in white matter over lifetime and probable white matter tracts (diffusion tractography).
What does an fMRI measure? How does it work in general, what does subtraction have to do
with it? What process is used to visualize brain processing via BOLD imaging?
Measures oxygen consumption in the brain to provide a moving and detailed image of the brain.By doing so it measures functional parts of the brain. You take a baseline fMRI to see what parts of the brain are active, give a task or elicit a response and use subtraction to see what parts are stimulated. Subtraction: after giving the task to the individual or eliciting the response from the individual you take the scan you take all of the active parts you get from the scan and take the intersection of scans from after the task and the baseline and subtract it from the scans after the task.
-BOLD: measures brain activity w / MRI by blood O2 lvls
~more O2 used in one area= more/higher activity in that region
-different from MRI; fMRI measures function
What is difficult about an fMRI for patients, and what effect does this have for ability to use
fMRI?
They’re very noisy, and in a very small enclosed space, you must be very still, and you can’t get one if you have metal in your body. Babies, children, the elderly, people with certain disorders, and people with metal all cannot participate in this. Also bad dense tattoos aren’t allowed
What are the various fMRI research approaches? What different things are revealed by task-
based and resting-state research approaches?
Task based approaches: majority of research, studies activation levels.
Resting state approaches: brain connectivity
MVPA (multivoxel pattern analysis): varying a task slightly, you see whether or not there is a change in pattern of activation (not 100% sure)
Why do resting state approaches for an fmri allow for testing of different groups of people?
The time it takes to do these tests is a lot shorter, so more people are able to stand it
Why would brain connectivity be of interest to researchers?
You get to see the various communications between brain regions
How does a PET work? What is PET used for? What are the advantages and disadvantages of
PET? What is it that PET does that fMRIs do better?
position-emission tomography
process:
-inject radioative chemicals into body to visualize brain to show where brain blood is used more
-radioactively labels glucose and NT- substances= shows when tumors are metabolically active
advantages:
-noninvasive
-can distinguish malignant and benign tumors
-detects disease in early development
disadvantages:
-discomfort if claustrophobic or fear of needles and injections
-possible alergic reaction
-fMRI > PET in terms of resolution of image
Which two types of PET imaging are used in research for Alzheimer’s disease?
1) Amyloid PET imaging- measures amount of amyloid deposits in the brain
● Beta-amyloid- critical initiator for alzheimer’s (more amyloid buildup is an indicator of alzheimer’s starting)
2) FDG PET imaging- measures concentration of glucose (which indicates neural activity) in the brain (lack of glucose can indicate neural degeneration such as alzheimer’s)
What types of electrical recordings of brain activity are there (we mention 3)?
Single/multiple Cell Recording
Electroencephalograph (EEG) Recording
Event Related Potential (ERP) Recording
What is the general process in single cell recordings? Who is this process used with?
An electrode is inserted into the brain, adjacent to a neuron, the neurons activity is recording. Many individual neurons can be recorded simultaneously, and can record a single action potential or many action potentials.
Most commonly done with animals (Cats & rodents)
What is the general process in an EEG? What can be studied with EEGs?
EEGs record brain waves or electrical potentials. Measures group neurons from the scalp. EEGs can study sleep, epilepsy, monitoring the depth of anesthesia, and normal brain function.
ERP, what is it, how does it work? What is it used for?
“Event-Related Potentials” or “Evoke Response Potentials”
Brief change in a slow-wave EEG signal in response to a discrete sensory stimulus is classified as an ERP.
EXAMPLE: Auditory evoked potential, makes sounds and tracks where in the brain the signal responses.
What is function of averaging in ERPs? How is that like the subtraction process in fMRIs?
Averaging provides a more sophisticated method of extracting more specific sensory, cognitive, and motor events. Eliminates other types of sensory information in order to detect specific types of stimulus. ERPs are repeatedly taken and then the responses are averaged
What is magnetoencephalography? What is it used for?
Magnetoencephalography (MEG) is a non-invasive brain imaging technique that measures the magnetic fields produced by the brain’s electrical activity, providing precise information about when and where brain activity occurs. It’s used to map brain function, pinpoint the source of epilepsy-related seizures, and aid in planning surgeries for brain tumors and epilepsy
