字幕表 動画を再生する 英語字幕をプリント - The final guest video in this run is from Alie and Micah, a neuroscientist and a clinical therapist who run Neuro Transmissions. Their video has giant magnets, 3D printing, and a Star Wars action figure. Alie, Micah, it's all yours. - We're here at the Keck Center at UC San Diego. And this is a functional magnetic resonance imager, or an fMRI. - Well, functional, but not functioning. This is actually a dummy scanner that's used for educational and training purposes. An actual fMRI machine houses a 3-Tesla magnet that's more than 60,000 times more powerful than the Earth's magnetic field. And over 3,000 times more powerful than your average fridge magnet. If we were anywhere near the real deal, well, we would put our camera and our equipment at serious risk. - But why on earth would anyone possibly need a magnet so powerful? Well, some of the researchers here at UCSD are using fMRI to study the human brain in ways that 30 years ago just weren't even possible. - I'm Maggie, I'm a fourth-year graduate student at UC San Diego. - My name is Stephanie Nelli, I'm a sixth-year PhD student in John Serences' lab. - We study mostly selective attention and expectation and other cognitive factors and how they influence visual processing in humans. - My research is about really basic visual perception. How do we make sense of the world around us? How do we choose, out of the plethora of things that are constantly accosting our visual system, how does your brain make sense of the massive amount of information constantly bombarding it? fMRI itself was developed not very long ago, it's a very new technique, as far as human research goes. And it was developed in the '90s, I believe, actually in Bell Labs. - fMRI is a particular specialty of MRI called functional MRI, so what that does is basically, instead of measuring the difference between particular tissues, you're actually optimising to detect the difference between oxygenated vs. deoxygenated blood in a person's brain. - For a long time, it was impossible to look at the brain up close without cracking open someone's skull. [Micah laughs] And even if you got a brain from someone who's passed on, that's not all that useful for understanding how it works. When Leonardo Da Vinci dissected the human brain in the 16th century it was with the intention of finding the seat of the human soul. Spoiler alert, he didn't. - Unsurprisingly, the functions of different brain areas were essentially a mystery well after the scientific revolution. But fMRI changed all that by giving scientists the ability to see the brain working in real time, track activities in different brain regions, and read your mind. - No, unfortunately not for us scientists, an fMRI machine cannot read the mind. It can tell you basically where blood is being transported to in the brain. So which parts of the brain are active. - An fMRI scan can tell you when someone is doing some cognitive task, what kind of patterns of brain activity you see. So which areas are active, what information are those areas representing. For instance, if you have someone look at different images and you measure MRI while they do that, then later if you have that same person come in and you say, okay, think about something. Now, based on that information, I can guess what you were thinking about. - I could probably say you're looking to the left by looking at your neural activity or I could say you're looking at a horizontal line by looking at your neural activity. However, am I gonna be able to tell what you're daydreaming about or who you're in love with or something like that? No, I don't think think that's gonna happen in my lifetime but, you know, I said it on camera so we'll be able to... [laughs]. - It might not quite make sense how a magnet does all of this, so let's break down the process step by step. Let's say that Rey here has been having some neurologically linked problems and a doctor refers her for an fMRI. All of her Force powers are messing with her head. "Oh no, Kylo Ren keeps appearing in my mind! "I can't stop thinking about his hot torso. "Ohhh!" - The technicians place her on the table, give her some earplugs and stabilise her head so she can't move it at all. If the head moves during the scan, the images will come out fuzzy. Next, the table slides into this large, doughnut-shaped section which houses the ultra-powerful magnet. The strong magnetic field of this magnet then actually turns the hydrogen atoms in our blood. - Wait, what? - Yeah, the human body has a lot of hydrogen atoms because well, we're mostly made up of H₂O, that's water. The magnetic field from the fMRI interacts with the protons in the hydrogen atoms and makes those protons essentially point in the same direction. That's right, your molecules are magnetic. Hence, the magnetic resonance part of magnetic resonance imaging. - Once Rey's in position, she'll hear a series of very loud clangs and beeps. [MRI machine beeps repeatedly] But these sounds aren't just the hottest new beat, they actually serve a purpose. Every clang you hear is a radio wave pulse being fired off. This radio wave disrupts the uniform direction of the protons and pushes them in slightly different directions. Here's the cool part. As the protons move back into realignment, they release their very own small radio signal and those signals are then detected by the fMRI machine's radio receiver, which starts taking snapshots of cross-sections of your brain, which you hear as the beeping sound. After some complicated computation, what shows up on the computer screen is a series of images that show both the anatomy of your brain and highlighted areas where there's more blood flow. Pretty cool, right? - Yeah, so fMRI doesn't actually measure your brain activity. It can't detect your individual neurons firing, as cool as that would be. fMRI machines actually detect what's called the BOLD signal. - So the BOLD signal stands for blood-oxygen-level dependent signal and it's basically an index of how much oxygenated haemoglobin is in a person's blood at a particular point in their brain. - Neurons themselves don't keep a high store of glucose hanging around so that they can do their job and so the blood vessels, through these things called astrocytes, actually, help supply neurons with the glucose and oxygen that they need to do their signalling. - When you have neural activity that happens in your brain, a bunch of blood will rush to that area and it turns out that oxygenated and deoxygenated haemoglobin in your blood have different magnetic properties. So deoxygenated haemoglobin will disrupt the magnetic field more than oxygenated haemoglobin will and it'll actually cause a decrease in the signal. So when you look at an fMRI image, the higher the signal you have, the more oxygen is in your blood at that point. And so you actually can measure with the BOLD signal after these neural events occur. That basically tells you how much energy was consumed at that location. - Now, it's not perfect. It can't detect changes instantaneously or tell you exactly what kinds of signals are being sent. - But even with its limitations, it lets us better understand which brain regions do what. Using fMRI, scientists have been able to identify 180 distinct brain regions. Better understanding the roles of different brain regions means that doctors can use that information to help treat and support patients with neurological disorders or brain injuries. fMRI technology is cool, but both of us wanted more. We wanted to get into the machine and see what our own brains looked like. Maggie and Steph asked me to participate in a pilot research study looking at how humans distinguish between faces and I jumped at the chance to help out. - I didn't participate in the study but I was able to get a structural scan. It doesn't measure blood flow but it does give you a high resolution image of your brain's anatomy. It was a strange experience, being inside. It felt like being in a plastic coffin. I can see why some people get claustrophobic. - And participating in the study was harder than I expected. While the task I was doing was easy, it was hard to stay focused on doing the same thing over and over for almost two hours. But it was also really cool to see the results. - And yet, we could not pass up on the opportunity of a lifetime. - I mean, sure it's cool to see your brain on a screen but imagine holding it in your hands. What does my own unique brain really look like? Well, as it turns out, we're able to find out. - Thanks to modern software, we're able to take the 2D slices of our brains and compose them into a 3D render and print them out. Cue the time lapse. - Well, look at that beautiful brain. - I really liked how the rainbow filament turned out on this. - Yeah, it's so pretty. - This turned out really cool. - I know, and I really like my glow-in-the-dark print. It's super bright. - The grooves are much wider in yours, and not quite as tightly packed, whereas mine is super tightly folded. - It's cool that you can see the inside too, the hippocampus and all these different brain regions. - Obviously I knew that my brain wasn't perfectly symmetrical, no one's brain is, but you can really see very obvious differences. It's really interesting to see, like, oh, that's my brain's shape. - Right, I didn't really think about that before. - Every time someone comes over to our house I'll be like, did you see my brain? - Lemme show you my brain. - Lemme show you my brain! - It's incredible that we have the technology to track the activity of a live human brain. fMRI has pushed neuroscience to new heights and has given us a glimpse into the seat of human consciousness. And only somewhat less incredible is the fact that we can use those same images to build 3D models so we can create a life-size version of our own brains. How funny that just a chunk of squishy cells this big can come up with such incredible tools to help us better understand our minds and ourselves. - Huge thanks to Maggie and Steph from the Serences lab for their expertise and to UCSD for giving us access to their scanner. And thanks to Tom for giving nerds like us the chance to share our brainy love. Maybe we'll see you later? - Maybe? - Until next time, we're Neuro Transmissions, over and out. - Thank you folks, go subscribe to Neuro Transmissions. I would recommend starting with Micah's video on training a cat to high five or Alie's video on how marijuana affects your brain. And that's it! I'm back next week and I will see you then.