If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:5:18

Video transcript

today we have many different ways of studying the brain and I want to go over a few of them here and in future videos we'll go into a lot more depth about each of these methods but I wanted to give you a quick overview of all of them in order to show you how they relate to one another and I'm going to split them into two broad categories those that tell us about brain structure and those that tell us about brain function and on the structural side we'll start with cat scans or CT scans which stands for computerized axial tomography and this method uses x-rays in order to create an image of the brain and this is super useful in that it can show us whether or not someone has a tumor or if there's Evan or mole swelling or bleeding but it can't tell us anything about what areas of the brain are active at a given time another way that we can look inside of the skull to look at brain structures is with magnetic resonance imaging or MRI and instead of using x-rays like a cat scan this method uses radio waves so a person's head is placed within a machine and they're exposed to a strong magnetic field and this magnetic fields causes the atoms in the brain to line up to align in a certain direction and after this is set up a radio wave is added to that magnetic field which disrupts the orientation of the atoms and as the atoms move back to align with that original magnetic field they emit a signal and most importantly different types of atoms emit different signals and this allows for the creation of a detailed picture of the brain much more detail than you would see with a cat scan but much like a cat scan while the MRI can give us a detailed image of the structure of the brain it also doesn't tell us anything about brain function it can tell us anything about what the brain is actually doing and to look at that we have to use different methodologies for example researchers can use electroencephalography or EEG in order to measure the electrical activity that is generated by neurons in the brain and this is done by placing electrodes on someone's scalp at predetermined positions usually by using a cap with electrodes that are filled with a conductive gel and unlike single cell recordings these electrodes are not invasive they don't have needles or anything they're just placed right on the scalp but because they are external to the brain because they're external to the cells they can't really tell us any about the activity of individual neurons or even groups of neurons instead they look at the sum total electrical fields that are generated from the brain and unlike structural methods like PET scans and MRIs we don't get a picture of the brain from an EEG instead we get these these wavy lines here and while they might look kind of random to you this is actually really meaningful for someone knows how to read them for example they can tell us whether or not a person is awake or asleep or they can identify if a person is having a seizure and it can even tell us if people are engaged in certain cognitive tasks another type of functional recording is Magneto and Cefalu Graffiti and this records the magnetic fields that are produced by the electrical currents in the brain and I don't mean to give you too many acronyms but these magnetic fields are measured using super conductive quantum interface devices which are also known as squids and this technique has a better resolution than EEG but it is also a lot more rare at least within the social sciences possibly because it requires a large machine and you need special shielding for the room that it's placed in but comparison EEG requires a lot less of a setup and you don't need to build a special room for it so we have structural imaging here and functional imaging here and one thing that you might be thinking is wouldn't it be great if we could combine them and we can and the most popular and well-known of these combined methods is fMRI which stands for functional magnetic resonance imaging so in this case we have the same structural image from the MRI but we can also look at which of these structures are active and the idea behind this is that neurons that are firing a lot so neurons that are working hard in any given moment require more oxygen than neurons that aren't really active and so by measuring the relative amounts of oxygenated to deoxygenated blood in the brain we can get an idea of what parts of the brain are active of what parts of the brain were using to do a certain task so there might not be a lot of activity in the visual cortex when someone has their eyes closed but when their eyes are open that area of the brain would light up on the fMRI the next type of methodology that is both structural and functional is positron emission tomography or PET scans and while on their own they can't really give us a super detailed structural image of the brain we can actually combine them with the structural technology that we talked about earlier like cat scans and MRIs and to do this technique a kind of radioactive glucose has injected into a person and since active cells naturally use more glucose because they're using up the most energy and need to replenish it we can directly see what areas of the brain are more active at a given point in time but even so fMRI is a lot more popular at least within the social sciences and this is probably because PET scans are a lot more invasive you actually need to inject someone with a substance and like I said in future videos we'll go back and discuss each of these techniques in a lot more detail but hopefully this gives you a good idea of how each of these different methods work and what they can be used to study