Psychology RQ - Exam 2 (Lecture 10 - 18)

RQ - Exam 2 (Lecture 10 - 18) Class 10 - Brain visualization Visualization of brain 1. 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? o A thin x-ray machine goes around the person and shoots thin “slices” of x­rays through the head and computers are needed to interpret the data, along with electronic detectors (not film). The discrimination between brain structures is superior in CT scans when compared to x­rays o This gives you much better resolution than an X-ray (you can see much more w CT scan than just a plain x-ray) o Both have radiation 2. Which has the higher radiation dose: a skull X-ray or a head CT? why is that? o A head CT has a higher radiation dose o WHY?? 3. How in general does an MRI work? o A powerful magnetic field around the head aligns the hydrogen atoms in water molecules, then the field is shut off. Termination of radiofrequency signal causes nuclear atoms to return to original state, releasing electromagnetic energy in the process. o When the atoms snap back to their original positions, energy is released, and that energy is measure and a picture is constructed. o NOTE: an MRI is applicable to any body organ 4. What are the advantages of MRIs? o No X-Rays. Safe, very clear picture (detailed) o There is no radiation being used, resolution is very high and you can now see small bleeds and edemas with MRIs 5. What does an fMRI measure? How does it work in general, what does subtraction have to do with it? o fMRIs measure Oxygen consumption (which is a proxy for the the function of the brain) and blood flow (CBF) in the brain – it reveals the level of activity of a particular brain region, as well as the size and appearance of various areas of the brain. o An fMRI machine takes a series of pictures of the brain which makes the oxygen consumption in different parts of the brain visible. o You take a baseline fMRI to see what parts of the brain are active, give a task or elicit a response and use subtraction (from the picture that you get while doing the task) to see what parts are stimulated. - ensure that a given task or stimulus is responsible for the activity in a particular part of the brain. 6. What is difficult about an fMRI for patients, and what effect does this have for ability to use fMRI? o You need to lie absolutely still while being in the fMRI, in most cases it is very hard to do so – it is required that you bite on a bite bar to keep the head very still – a lot of people we would like to scan, cannot be scanned (it is also terribly noisy and claustrophobic) – two­year olds, a person with dementia (we are very interested in looking at their brains, but it will be very difficult to get them into an fMRI and get them to keep still) – it is hard to scan people with intellectual disabilities and those are the people we are very interested in scanning o Recognize why these are more difficult to take ** 7. What does a DTI visualize? How is this useful? o A DTI is an MRI in which water diffusion at a location is calculated. DTIs show the preferred location of diffusion and allows for visualization of directional fibers. It is an MRI with a different algorithm – it makes white matter tracts visible and shows directional fibers. 8. How does a PET work? What is PET used for? o Radioactively labeled sugars are injected. As they are used up they emit positrons, and since activity in the brain requires both glucose (sugars) and oxygen, this allows for imaging of the brain.  (uses glucose, which your body likes to use for energy – and you look at where the sugar is being used) – this told us which bit of brain was using the energy which means it shows a functional picture o Tumors use a lot of glucose, so they stand out especially well on PET scans 9. What is TMS? What in general is the process? What is it used for? o Transcranial Magnetic Stimulation – only one that has anything to do with stimulation o This is the activation of intense magnetic fields to temporarily inactivate neurons – in other words, putting an intense magnetic field in an area to shut down the neurons for x amount of time EEG 10. What types of electrical recordings of brain activity are there (we mention 3)? o SCR – Single Cell Recording o EEG – Electro Encephalograph o ERP – Event Related Potential 11. What is the general process in single cell recordings? Who is this process used with? o An electrode is inserted into the brain, adjacent to a neuron, and the neuron's activity is recorded (how many times the neuron fires). This can record a single or many action potentials. Many individual neurons can be recorded at the same time. o This is commonly done on animals // this is not usually done in humans. 12. What is the general process in an EEG? What can be studied with EEGs? o EEG records electrical potentials or “brain waves” in the brain. You are measuring a bunch of neurons that are somewhat firing simultaneously – you measure collective activity of neurons in the cortex.  You get a cap on your head, and in order for the electrode to pick up the signal there is a gel that is applied that picks up the signal – the information flow is recording any electrical signal from your scalp o Extremely useful for sleep studies, epilepsy, measuring levels of consciousness. 13. ERP, what is it, how does it work? o A brief change in a slow-wave EEG signal in r