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Video transcript

- [Voiceover] 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 abnormal 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 field causes the atoms in the brain to line up, to align in a certain direction. And, after this is setup 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't 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 cells 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 anything 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 CAT 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 who knows how to read them. For example, they can tell us whether or not a person is a 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 congnitive tasks. Another type of functional recording is Magnetoencephalography or MEG. 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 measureed using Superconductive Quantum Interface Devices, which are also know 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. By comparison, EEG requires a lot less of a set up, and you don't need a special room for it. So, we have structural imaging here, and functional imaging here, and one thing 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 at 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 we're 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 is 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.