Dr. Jerry Yakel — Acetylcholine Receptors and Neurological Disease

Monday, January 27, 2020

The neurons in our brains use both electrical and chemical signals to communicate. When those signals are not generated or interpreted correctly, serious problems can arise. Dr. Jerry Yakel is a neurobiologist studying acetylcholine receptors, which allow neurons to turn signals transmitted using the chemical acetylcholine into electrical messages. Because acetylcholine receptors are found on so many nerve cells, numerous neurological disorders can arise when they fail to work properly, including Alzheimer’s, Parkinson’s, and epilepsy. By studying these receptors, Dr. Yakel’s team hopes to better understand how they contribute to disease, which could eventually lead to therapies for a variety of neurological conditions.

Jerry Yakel, Ph.D., is a Senior Investigator in the Ion Channel Physiology Group at the NIH’s National Institute of Environmental Health Sciences (NIEHS). Learn more about Dr. Yakel and his research at https://irp.nih.gov/pi/jerrel-yakel

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Transcript

>> Hi, Dr. Yakel.

>> How are you?

>> Thank you for having us here at the NIEHS campus.

>> My pleasure.

>> It's good to meet you.

>> You too.

>> Although we met a few years ago. But this is a little bit more interesting because I'll get to talk to you for a little longer.

>> Yeah, yeah. That's great for me.

>> So you've been married for 31 years?

>> Yes. I'm proud of that, 31 years. I met my wife in Oregon State University, Corvallis, Oregon, in 1980.

>> Oh, that's the year I was born.

>> Yep, I know that people in my lab, usually I met my wife before they were born.

>> And the two of you like to travel a lot?

>> A lot, yeah. And we like food and wine. And when I was a post-doc in Portland, Oregon, we picked grapes and actually made wine in the cellar, so we're pretty committed to that.

>> How did it turn out?

>> Spectacular actually.

>> Yeah.

>> As a scientist, making wine is only a couple steps. And if you just follow the cookbook very simply, then it's not too difficult. As they say, the work's already done for you. Your job is just not to mess it up.

>> Yeah. So where's one of your favorite places to travel?

>> I don't have one favorite place. So I've lived and worked in Europe. And my wife and I love traveling to Europe. But sort of our favorite place now is South Pacific. We like the sun and fun vacations.

>> Oh, yeah.

>> And so we've been lucky to be able to go to the South Pacific a couple times. You know, Bora Bora. Moorea. Tahiti. That, so that's the place to be.

>> Yeah, I bet.

>> Yeah. That's, the pictures of that place, it’s just beyond words so. You know, if there's one place on Earth, probably that would be the place.

>> Yeah. Yeah, and the campus here at NIEHS is very beautiful as well. You've got a lake, and surrounded by trees.

 >> We feel special. I mean, we lose a little bit by not being at what I call the mother ship, the main campus. But day in and day out, it's beautiful. We have a lake. You can take walks around the lake. And for neuroscience, we have great universities very close by — UNC, Chapel Hill, Duke, NC State — so the community for neuroscience here is spectacular. So we have the best of both worlds as far as I can see. We don't have to worry about parking.

>> And did you say that you had been here at the NIEHS for 25 years, is it?

>> Yes, 25-plus now, so.

>> What originally brought you here to do your research?

>> Like a lot of people I train, I got my Ph.D. at UCLA. I did a post-doc in Paris, France. Which was spectacular. And then in Portland, Oregon. But then you start looking for jobs, you look for the best place. Which takes into account your professional life. My daughter was born in Portland, Oregon. So family, lifestyle, and all that. And then you start looking for jobs, and then you get offered more than one, hopefully. So it had the best overall lifestyle, professional attributes. So I knew pretty much that the intramural program was a place that I thought would be serious. My thesis advisor had worked in the intramural program. What you hear most from scientists about the difficulty of their life is applying for grant money. And that was the one thing I knew at the NIH, how wonderful the intramural program is, is I'm not spending a third of my time or more just getting funding to do my science. We do science, and that's what we do. And so that was extremely attractive to me. And my boss, who brought me here at the time, David Armstrong, who was a post-doc at UCLA when I was a graduate student. He's actually the main reason I came here. He was in the Laboratory of Signal Transduction. And I was brought here to, you know, do some science on some of the things I was interested in. And so it was a great, great opportunity.

>> Do you remember what was the initial spark that got you interested in neuroscience?

 >> I have a story. I call it the light bulb moment that I always tell. So it will take a few minutes, if you don't mind.

>> Oh, sure. Take your time.

>> My dad was a police officer. My mom worked in schools. No one had, you know, education beyond maybe a Bachelor's degree. My dad now has a Master's. But I had no idea what it took to be a scientist. So we camped a lot. I grew up in Southern California, as I said. We had a sailboat. We were on the ocean water a lot, so I thought I wanted to be a marine biologist. I liked whales and that. As I got through, I ran track. So I actually went to community college for the first couple years in Southern California. I didn't know what I wanted to do with my life. And I had great biology and chemistry teachers, and so I knew biology was something I was interested in. I had this bug collection in high school that I loved, collecting bugs. Felt like a real scientist. And then my dad got a chief of police job in a small town, central Oregon — Lebanon, Oregon. And so then I didn't have any other goal in mind, so I went to Oregon State University, which turned out to be lucky for me because I met my wife there eventually. So--and I got into a biology program. And I took an extra half year for different reasons we don't need to go into, but I had a little bit of time. So my animal physiology teacher was teaching a graduate course in neurobiology. He liked me. And that's what changed, because the graduate course in neurobiology, we did two things. We read real research papers in Nature and in Science, so real science, what was being done at the time. And the technique that I use in my lab was being invented, if you will, at the time. We can get into that later, if you like. The other thing was we actually did real experiments. So I did the very first recording for a nerve cell that I ever had done. And I'll never forget to this day when I did the first recording. So nerve cells are what we call excitable. They have electrical currents that they run down, and they talk to the next nerve cell. We call it a spike or action potential. It's a unit of the nervous system. And the first time I inserted an electrode inside a nerve cell from an aplysia — a sea cucumber — and I recorded the action potential, I went nuts.

>> Yeah.

>> I went nuts. I really--and I always say, when I talk to students, I didn't think I was smart enough. I didn't know how I was going to do it. But if I was going to be a scientist, I was going to be a neuroscientist. Study electrical properties of nerve cells. And I still don't know to this day why that's what I set on. But I love understanding how the brain works and all that. But it's studying the electrical properties of nerve cells and how they're connected in networks. And it's that day where I got the first recording, I saw that action potential. I literally--I'm running down the hallway. I was doing a Bachelor science project for, you know, getting my Bachelor’s degree. And I was doing some turnover of cell surface macromolecules. But that's the day I knew what I wanted to do. I hadn't applied to graduate school. I had no idea what to do. I thought I would take a year off to make money. I didn't make any money, so I went back to Southern California. I worked with my girlfriend at the time — now wife's — father who's an inventor. Then I enrolled in the UCLA graduate school. Luckily got in. And then I'm now a neuroscientist here at the NIH. So it was the this idea of this electrical properties of living nerve cells in this invertebrate, but it's the same basic properties cells in our brain use to communicate with each other.

>> What does that recording look like? It pops up on the screen as some jagged lines or--?

>> It's like a blip, you know. Literally like just a spike. So long story short, the insides of nerve cells are negative millivolt, 50 or 60 millivolt. A car battery's 12 volts. So when you basically short that circuit, you get current flow from the positive and the negative and in the cathode. So nerve cells basically work on the same principle. The electrical current comes from salts — sodium, calcium and potassium — that flow across the membrane. So the insides of nerve cells are negative. So ion channels is what my life is studying. They're proteins in the surface of nerve cells that are literally pores, like shutters on a camera, and they open and close, and when they open, then the flow of ions can go in the direction that the chemical and electrical gradient determines. So what happens is you have a cell that's about minus-60 millivolts on the inside. It's very high in potassium. Low in sodium. It's opposite on the outside. So what's literally happening when a cell becomes excited is these sodium channels open. There's an influx of sodium, so the resting potential goes from minus-60 to plus-50. And then those channels turn off. And potassium channels open to bring it right back down. So it's literally like a triangular kind of a shape. There's more detail than that. But we call it an action potential. That was coined in the 30s or 40s or 50s. I don't know my history on that very well. Or a spike. And literally, depending on your time register, it can look like just like spikes when the cells excite. So what happens to our, in the cells in our brain is a signal is created down a nerve cell. A chemical signal is released. It excites the next cell to generate the spike. And then it goes down the merry way in a circuit. The brain basically is a whole bunch of circuits of neurons connected in different ways. And you have chemical signaling molecules called neurotransmitters that determine excitability. And the neurons are electrically wired at junctions called synapses. And so we study the flow of information within a nerve cell. Because some nerve cells are pretty long. Like you have sensors in the bottom of our foot that go into your spinal cord. Some of these processes are, you know, several feet long. So the electrical signal, the spike literally is the flow of information from one end to the other. Has to go pretty fast. So that spike, that action potential, is the thing that we are measuring in these neurons that serve as the basis of the electrical excitability of the nervous system. So that's--I know it's kind of a long explanation. But, you know, that's sort of, that's what the signals we're looking at are that you can see. And you can tell that the cell’s alive and it's active. And I can excite it myself. And the cell responds and talks back and forth. It's quite amazing actually.

>> So are all of the--are all the neurons, do they all have the same sort of action potential where it's sodium and potassium? Or are there different ions?

>> Nothing's 100 percent. So I'm going to say mostly yes. Sometimes there are calcium spikes because calcium is a divalent cation. It will do the same kind of thing. For the most part just sodium and potassium. Sodium turns on really fast to depolarize, and then it turns off, and potassium turns off to repolarize. And these gradients are set by ATPases and stuff. Which, you know, basically take the sodium and extrude it from the cell, and then potassium is increased inside. So you set up this potential gradient, which is the energy with which the ion will flow, to determine whether a cell hyperpolarizes or repolarizes. So, you know, you have this built-in potential across the nerve cell membrane. And the cells are quiet and just sitting there. And then, when a signal comes to open up these channels and then, you know, stuff happens.

>> Yeah.

>> Your electrical excitability.

>> What are some diseases or health problems that are applicable to the type of research you're doing? What are you trying to discover or uncover about these processes?

>> So I head the department. So I'll tell you a little bit about what different people, including myself, do.

>> Sure.

>> As I told you, there's different chemical signals. We call them neurotransmitters. There's dopamine. There's norepinephrine. There's acetylcholine. So, for example, in Parkinson's disease, the neurons that make and release dopamine die. And the dopamine circuits that these cells are connected to control motor movement. So people with Parkinson's — pretty late-stage Parkinson's — they have motor movement control. So one of my PIs, Guohong Cui, is trying to understand the dopaminergic circuit. Another PI, Patricia Jensen, is studying the noradrenergic circuit. Norepinephrine's another neurotransmitter linked with anxiety and depression and that. So my own neurotransmitter of interest is acetylcholine. So the area of the brain I'm interested in, the hippocampus, is where a lot of learning and memory occurs. And in patients with Alzheimer's disease, the cholinergic circuit in the hippocampus and related areas is dysfunctional. So if we can understand the cholinergic circuit so well, the basic circuits--so many of us are pretty basic-oriented. We're not directly studying the disease process. It's basic because we can't understand how brain circuit goes wrong until we know how it works in a normal condition. So that's sort of the basic science approach. So I'm trying to understand how the cholinergic circuit in the hippocampus is set up--how it's set up, how it's regulated, modulated. So then with animal models of disease — Alzheimer's disease — we can try to find out how to mitigate the, you know, the cognitive deficits in Alzheimer's, or even cure the disease. So that's my own research. We have an eye towards Alzheimer's disease mechanisms and cholinergic dysfunction. Others in my department, dopaminergic dysfunction and perhaps Parkinson's disease cures, or mitigating some of the dysfunctions in Parkinson's, you know, anxiety and that kind of thing. So we're trying to hit--we're a pretty small department at the moment, but we're trying to hit some of the basic diseases. Most diseases have a genetic component, but the genetic component is very small, so everything else must be environmental — diet, air, and all that. So we're also trying to understand some of the exposure etiology of some of these diseases. If you could really imagine, you'd rather prevent the disease from occurring in the first place rather than trying to cure it after it happens or mitigate the side effects. So, you know, we're trying to understand how these circuits in the brain form developmentally, how they're maintained. And then with aging, of course, they all, you know, they start to have issues with aging. We're trying to understand the aging process, all bits and pieces of it. That's the way I would answer that. But from a basic approach, understand the basic circuitry. And most of the PIs in my department — in fact, all — use rodent models. You know, they're pretty similar in many ways to the human condition. But then the work that we discover, the information we discover, hopefully in a translational approach, will be taken into humans. And then that's where you really get the kinds of answers to help treat people.

>> Do you remember maybe what was one of your favorite moments in the lab, aside from your very early discovery that you could excite a neuron? But here at the NIH, what's one of the more memorable discoveries that you or your team has come across?

 >> Yeah, I don't have one favorite, you know, but I remember some of the hallmarks along the way. For example, some of the receptors, they're called cholinergic receptors. And so, for a lot of these receptors, you have direct ion channels they link to and these metabotropic kind of G-protein-coupled receptors: muscarinic and nicotinic. My lab's spent about 20 years studying nicotinic receptors pretty much in isolation, and this is interesting because when nicotine acts in the brain, it's through nicotinic receptors. And, of course, nicotine is bad and nobody should smoke. It's addictive and it kills. But nicotine can also improve some cognitive performance. And so that's where I was quite interested in early on, was how nicotine and nicotinic receptor action improve memory and things like that. So the--sort of the first paper was in 1997 in my lab, was where we were one of the first to discover some types of interneurons in the hippocampus that actually had nicotinic receptors. Until then, it had really been thought that nicotinic receptors didn't directly conduct a synaptic transmission, they more modulated it. So we were one of the first papers in 1997 to show that the interneurons — these inhibitory interneurons of the hippocampus — really had large proportions of these nicotinic receptors. So that was one of the ones put me, my whole lab, basically in the nicotinic field. We've had discoveries where we show beta amyloid peptide, which is involved in Alzheimer's disease, inhibited nicotinic receptors. You know, there's a whole bunch of things along the way, you know, and they're all very exciting. So there's not any one thing. I sort of always point to that first paper in '97, which really got me in the nicotinic field. And I'm still there.

>> So in Alzheimer's there's--that occurs in the hippocampus; is that right?

>> So the input, the cholinergic inputs come from the medial septum-diagonal band of Broca, so the septum for short. The cholinergic neurons there, the health of the cholinergic circuit there, and the inputs from the septum to the hippocampus — that's sort of the circuit that we're interested in studying. And so it's the septum, the hippocampal circuit, and then the underlying cortex is called the entorhinal cortex. So we're really in that sort of area right there, the hippocampus sort of at the center. It's an area where a lot of people study, yes, but it's an integration center for a lot of circuits of the brain, other areas of the brain. The amygdala, which is involved in fear conditioning, has feedback into the hippocampus. The prefrontal cortex for executive decision-making. So the hippocampus seems to be like a way station. Long-term memory is not really stored there, but a lot of the comparisons, you know, there's associative kind of learning we have. This happens and then this soon after. Then its encoded in the hippocampus. So information comes in there from many different places. It's compared and encoded, and then it goes stored elsewhere. So we're very interested in how information comes in, how it's processed, and how it goes out. That's--we're sort of having many, many kinds of tools — functional tools, imaging tools, genetic tools. But, in general, we're trying to study the flow. I mean, these are millions and millions and millions of cells firing at the same time, so it's challenging. But in a sense, by the different techniques we have, we're really--I think of it like a freeway system in L.A. There's all kinds of stuff going on. But we're trying to monitor literally the flow of information that comes in from all different areas. How it sort of oscillates, and how you get synchrony, because you start to see this synchronous output when associative kinds of things happen at the same time, and then the information is processed. So we're, again, we're just trying to study the flow. Like, for example, sleep's one of our projects. So when you learn something during the day, most of that information is sort of useless. You know, if you only have so much memory, you can't save everything. So information comes in. And then, you know, then it's encoded. And then it goes out, and it's consolidated — the idea where the memories that you want to keep are stored, and everything else sort of gets thrown away. So we're sort of interested in that. And it's sort of a reverse. Cholinergic input's important. So in the sense during-the-day information--this is over generalization, but information comes in during encoding, and it's sort of the same general pathway, it seems to go in the reverse direction at night in sleep. And acetylcholine seems to be —overly simplistically — but it seems to be a gateway that regulates the flow of information during encoding and consolidation. And that's really important because if that goes awry, if you don't sleep well, you know, you start to have memory issues: short, acute and long-term. So that's a kind of thing that these neurotransmitters systems are regulating: the flow of information in that circuit. And we're just trying to use different techniques to look at how activity is processed — how it's pattern-matched and, you know, what impact that has. So that's what we're trying to do.

>> So what would you say a memory is in the brain?

>> Oh, yeah, I know. Well, it's an associative kind of thing. Like I think of, like, really niece meals my wife and I have had in small little villages somewhere, you know. So, you know, you can have the same food at home. It's not the same. So, you know, memories are something good. Or sometimes fear. Fear memory is very, very powerful. You know, people go into a war situation, and they hear an explosion.

>> Some trauma.

>> And then they go to like the Fourth of July, where they know it's not a dangerous situation, but it triggers that fear. So in that case--there are movies about that, getting rid of memory, you know. "Men in Black" or something like that, you know. Some memories you want to get rid of. And that's some of the therapy people are working on. Other memories, like goods ones, you want to remember. So, you know, there's some kind of coding for time and space, there's visceral encoding, smells. sight and vision. So memory is sort of like an engram, they call it. It's a little bit of everything. And I don't know if anybody really knows exactly why certain things are kept and some things aren't. Like I remember my phone number from when I was in grade school, but I can't really remember my phone number now, so there's something that happens--the special memories that are stored early on and then as you get older. So I don't really know. I don't know if anybody really knows exactly how memory's stored yet. There are a lot of smart mathematical people that come up with ideas about that. I don't really know where it's actually stored. I'm just trying to find one of the relay stations that starts a match up these different things and enhance an output. We're just at that level basically. We're trying to look at the cellular level of that. So as far as what really, how memory is, I don't even spend a lot of time really thinking of that because it's too complicated. It's sort of the brain trying to understand itself, you know what I mean. It's just, I just, I don't think about actual memory. Other people do that kind of thing. I'm really circuit based. I'm thinking of the proteins and the cell membrane, the cells themselves, how the cells are connected, and how the circuits flow. I'm a very cellular neuroscientist from that perspective. I mean, it's a great question. We'd all like to know, but I try not to think about it too much because it's just, kind of, you just, I don't know. I think of the hippocampus as more--as a pattern-matching kind of way station, if you will, not necessarily the long-term memory store.

>> And you probably already kind of described this, but what do you mean by it's a ‘pattern-matching’ way station? So stuff that is coming in and out of there, what's the patterns that are being matched up?

>> Well, like dog, Pavlovian conditioning.

>> Oh, got you.

>> You can get a dog to salivate when he hears a tone because you trained it. You tone, and you give it food, you tone, and that kind of thing. So we have a lot of mazes, you know, we have different kinds of rewards. So you can get mice to do really amazing things with touch screens. You can get them to poke out a pretty sophisticated pattern when they get a reward at the end. So it's matching something that they do successfully and get a reward, that kind of thing. If you don't give them reward--like foot shock, so, you know, they're not afraid of light necessarily, but if you pair a light or a tone with a foot shock, pretty soon they'll be jumping when they hear the tone even though there's no--that kind of thing. That's what I mean ‘pattern.’ Again, certain fearful kinds of things. You know, you step into the street, a car almost ran you over, you remember that, and that can be a survival circuit. You'll probably be careful the next time you go into the street. As I shared with you, I broke my foot a year ago today jogging. That space, that place where I did that, I'll always remember that. And that can be part of survival. And for pleasant things too — you remember certain trips are good and all that. So that's what I mean. And memories aren't just sight. It's smell, sounds, and everything else. That's what I mean. It's sometimes a little more, sort of, the fear conditioning’s a little more instantaneous. You can kind of really understand that: these two things happen, don't do that again.

>> Is there anything that you've learned in your research or from overseeing or contributing to your larger group's research that you then turn around and apply to your own life? Whether it's diet, or any--I know you're doing very basic research, so it's kind of a ways off, but trying to optimize your own acetylcholine levels or dopamine or anything like that?

>> Yeah, I haven't done that. That's a great question. I haven't really applied that so much. But there are people--like I know some scientists who either have Parkinson's in their family or they themselves have, and they're really trying to understand the dopaminergic system. There are other people--they may not necessarily be scientists, but they work here, and they try to learn, so they try to take herbal medicines or something that might do that. So that's a good question. For me, I don't really try to alter my cholinergic system too much. Like, for example, pesticides can be cholinesterase inhibitors. That's bad for cognitive function. Nerve gas agents actually work through messing up cholinergic levels, so you can't mess with the cholinergic levels too much. On the other hand, different kinds of cholinesterase drugs enhance acetylcholine, and if you have Alzheimer's disease or someone has it, they can improve cognitive function a little bit, but it's one of those things, it's really hard to play with. The brain is so perfectly balanced, I don't think I'd really want to mess with that too much myself.

>> Yeah, yeah.

>> But it just depends, you know. If we find a spectacular--like I said, nicotine is not good, but if you find a nicotinic ligand, which improves cognitive function, you know, and you can get that out in the market, you know, would you do that? It's always a question ethically. Should this information only be used for people that have cognitive disabilities because of disease? Or should normal people be able to take things to improve their own memory, you know, like doping in rode cycling. That kind of thing. That's one of those questions so.

>> Yeah. Because there's a lot of supplements that, you know, claim that they--

>> Purport to do that, yeah. I know, I know. And one has to be skeptical about most of that but.

>> Does diet have a big influence on the levels of, like, sodium and potassium in your brain cells and choline?

>> Almost certainly. Almost certainly. It's mostly though just being healthy, you know, just being really healthy. Good, you know, good sleep habits, and eat well.

>> Which kind of affects everything.

>> Everything. Right.

>> All your systems.

>> Not--try not to be too overweight. That kind of thing. Everything needs to be pretty much in balance. There are certain conditions where the ionic gradients go awry. But that's really bad usually. That's pretty bad, late-stage. That's usually not something you or I could control precisely ourselves.

>> How do you get a single brain cell and maintain it alive? And stimulate it?

>> Most of what we do are brain slides. So, you know, you're trying to study the whole brain if possible. But there really isn't access. The kind of technique we use in my lab, which is this patch clamp physiology. It requires a neuronal surface that's free of extracellular membrane. So you could take a bit of the brain and enzyme-treat it and dissociate individual cells, and they'll stick to the bottom of the dish. This is cell culture. You can do it that way, and as long as you give the cell, you know, a balanced salt solution for ionic control — you give it a little bit of sugar, and, you know, a little bit of food – they'll stay alive for weeks in a culture dish. So you could do it that way, but it's a cell completely outside of its environment. Most of what we do in my lab are what we call brain slices. So you take a part of the brain, and we have a really, really sophisticated kind of a microtome. That--it's like a razor blade, fancy razor blade that vibrates at the same time as it's slicing through. There's some damage on the surface, but it's pretty minimal. We do about a 3- or 400-micron thick slice, puts it on its side, and then if you've done it well and you've done it fast — because you’ve got to get it out of the brain fast and get it into your bubbling solution fast — the surface of the slice will be pretty good. So then you'll go in, and some neurons will be poking out of the slice. And with the high optics, high magnification, 40- power with some good optics on there, you can see a micron, 20-micron-diameter nerve cell pretty easy. And it's mostly alive. A dead nerve cell, you can easily tell. It loses integrity. So you can see nice healthy cells in there. And so it's a brain slice, and you can keep brain slices alive too if you want. You can do them acutely, same day. Or you can culture them and keep them alive. So that's--it's not as hard as it seems.

>> Are there any other technologies that you use in your research?

>> So besides measuring electrical currents across nerve cell membranes, almost everything we do is imaging now. So what's imaging? Fluorescent imaging. So you can put fluorescent markers in cholinergic neurons  — we don't have to go into the genetics of that — so that all cholinergic neurons will be either fluoresced green or red. Or we can put in some kind of fluorescent sensors that, when calcium goes up, they will fluoresce green. So there's all kinds of fluorescent indicators now. There's fluorescent indicators if two proteins are close to each other. You can sense that. So we use fluorescent imaging all the time for studying, you know, fiber pathways. And we can even do things now--this is a technique called optogenetics that's going to win the Nobel Prize in the near future. Basically a jellyfish and some algaes have these light-sensitive proteins channels in them. So it's an ion channel that conducts sodium or potassium and has a light fluorophore, and when you shine like a blue light on this molecule, it will open up this ion channel. So we can go in and genetically put these kind of effector molecules — they're called channel rhodopsins — in, say, cholinergic neurons. And if I shine a blue laser light on that, only the cholinergic neurons will be excited. So we have even effector molecules. So you have fluorescent sensors that just sense changes in the environment — calcium and other things, or cyclic AMP — and we also have effector molecules. So this is like the hope of the future. I know we--it's hard infecting a human brain with proteins. But, you know, these are the kinds of things people are thinking. Let's say your number of dopamine neurons are going down, or they're not working as well as they should, if you could come in and be able to excite subsets of circuits. Or in an epileptic patient, you know, it's a hyperexcitable circuit you want to quiet. If you could somehow get in these effector molecules and with a little fiber optic probe silence the circuits with these effector molecules. That's sort of the dream of the future. So we use fluorescent imaging a lot. Both as a read out — as a way to give us the neuron anatomical connections — and to actually even excite selectively some kinds of nerve cells over the other. And measure the outcome. So imaging is part and parcel with going with the physiology and the electrical recordings that we do. And now we're all having to do behavior. It used to be where some labs like mine were just cellular, and other labs were behavior and in vivo. Nowadays, in high-impact journals, you really have to go from cellular all the way up — whole animal experiments. So we can actually put these effector molecules in living animals, put in probes, and not only can we measure circuit activity when an animal's going through a maze — you know, to try to find out if a circuit's active and how and when it's performing a function — we can actually even put effector molecules in certain circuits, as I've told you, and either enhance their memory or their cognitive ability or depress it. So we really can do amazing things these days in whole animal in vivo physiology. So we can--we're really starting to understand these circuits pretty well. And then we also have behavior because, at the end of the day, if I'm interested in learning and memory, we actually have to study these kinds of things in animals going through mazes or different kinds of things to study different aspects of learning and memory. So you basically have to go all the way from cellular or even sub-cell molecular ion channels all the way up through circuits to whole animal these days. And our department's able to do that. We have some cores that we can use with some expertise to help us, so one lab doesn't have to do everything. One lab sort of has a specialty here or there, but with the other PIs and the cores, we can pretty much do whatever we need to do in the department.

>> Is there anything in your department that is close to or might eventually be tried in humans in a clinical trial?

>> We're trying to get there. I mean, we're all pretty basic. None of us at the moment are really doing translational. But we have a clinical director, Janet Hall. We have access to the Clinical Center at the NIH. And every year we try to think more and more how might we do something. It is possible to do that. So we're thinking, all the time, how to do more translational work. So that's something we keep--you know, there's always a tendency to do what you're good at. And when you get outside the box, although we're supposed to be risk takers, we're often quite conservative in the sense of the science that we do because we're pretty good in a very tiny, tiny, narrow slice of the field. So jumping outside the box sometimes is a little terrifying. But we're trying to do that because the opportunities here are very, very good. And we also have Duke and UNC and the Clinical Center to be able to do that. So there are lots of opportunities. We just haven't quite done that yet.

>> So could you maybe tell me a little bit how you attach an effector molecule to a cell?

>> So, as I said, so these jellyfish, you know, they're guided to a light. Shrimp are guided to light. That's not magic. What it is in a simple way is that there's these ion channels. As I said, these nerve cells are basically units where the ions are controlled for gradients, potential. This is what will drive excitability. And neuron excitability can also drive muscles. And, you know, swim away or swim to. That kind of thing. So they've evolved these protein, these channels, that actually have an opsin on them. So the opsin is like the opsins in the back of your, you know, rods and cones in the back of--your rods. They sense--they absorb light, and there's a conformational change. So it turns out these channelrhodopsins, they have the opsin on the ion channel. It's in one protein molecule. So that's been cloned, and we can just put these proteins--we can, you know, with genetics, we can put lots of proteins in any nerve cell we want. So we simply put these channelrhodopsins in a nerve cell. And then with blue light — you know, you have to use the wavelength that excites them — with basically blue light for channelrhodopsin, which is the first one that I know of — there are other ones — blue light, this will depolarize the nerve cell. It will excite it. And that's how do you that. So all cholinergic neurons, let's just say, you put this channelrhodopsin in, and when I shine blue light on the whole slice, all the cholinergic neurons will excite right then and there. And then we can study the downstream effects of that, or we can study that in a whole animal. You know, we can alter their cognitive performance simply by exciting cholinergic neurons in a certain way. So there are these proteins. Algaes have these, jellyfish have these opsins, and there's different kinds that are just there. That's--no one's really inventing these new molecules. Those are in nature. That's one of the things that's quite amazing when you--different branches of science, and there are these amazing scientists that only do basic science, but they're going out, looking for tools. So the toolkit that we call it that's available to the neuroscientists these days are quite amazing --of how we can selectively activate or regulate subsets of circuits within the brain, and understand how those circuits participate in activities.

>> And so you do that through genetics to get the opsins attached to the cell?

>> Absolutely, yeah. That's, all basic neuroscience labs, basically, you have to use transgenic mice for different reasons. It's really complicated. In the olden days, we used, sort of, wild type rodents, and studied the properties of the nerve cells in them, and with these transgenic mice, they're designed so it's very easy genetically to infect only subsets of cells. And we can decide--we can breed in receptors, breed out receptors, effector molecules, proteins. We can really play with the genetics of an animal. Quite standard techniques nowadays. So we can easily get in by breeding. Or we can infect viruses. Viruses are very useful to labs now. A lot of these viruses, we--they're not dangerous anymore. Viruses often attack and infect certain nerve cells and nerve cells only. We like those kinds of viruses because we can now use these viruses because a virus will land on its receptor, and its genetic code will be brought into the cell. So the virus is just a vehicle for putting genetic material of our desire into these cells, and so we virally infect cells. Specifically, the cargo will be these effector molecules. And so we can see the cholinergic neurons. We can stimulate them with rhodopsin expression. If we're interested in calcium dynamics, we can put in a calcium sensor. It's quite amazing what we're able to do.

>> I don't know if you covered this or not. But you use a voltage-sensitive dye to record hippocampal excitability in circuits. Is there anything you can say about that?

>> As I told you, the basis of excitability is the membrane potential, okay, so if you're wanting to study--so the kind of electrophysiology I do is sort of one cell at a time. You put in a tip of an electrode inside a nerve cell. We measure the potential. We can see it depolarize and repolarize and that. That's good, but in the circuits of the hippocampus or any part the brain, you have thousands and thousands of cells. You can't possibly record from all them at the same time. So even though I love electrophysiology — it's a really high-resolution technique — sometimes if you want to just look at the overall circuit, you use dyes. Now, the voltage-sensitive dyes are getting better. They're not--they don't have the temporal-spatial resolution that we really need, but we've utilized them in the past to look at overall circuits. So, you know, you can get an average feeling of a circuit that's being depolarized, generally, with voltage-sensitive dyes. So, you know, that's some kind of sensors I said earlier. Calcium-sensitive dyes are actually much better. They have much better signal to noise. Voltage-sensitive dyes have a lot of improvement on them. Fundamentally, it's the voltage--we want to have a read out of the voltage of the whole circuits at the time, so those are really important. It's just that, for whatever reason, the chemistry of voltage-sensing dyes is such that it's just a particular difficult challenge to make a dye whose fluorescent readout changes dramatically. It's because--it's basically because it's right at the membrane. It’s only a very narrow area of the membrane — the plasma membrane — where the voltage gradient is, and that's all you need because that's where the ion channel proteins are, so you need to have a dye that's right there at the right place at the right time. And the voltage difference in the conformational change changes the fluorescent read out. It's just challenging. But that's also a great way of using these sensor molecules to measure voltage and calcium and cyclic AMP. So that's just, again, a read out for we can look at overall circuits dynamics — the voltage depolarization, repolarization dynamics. You know, that's a very important thing to be able to measure at the circuit level

>> Sounds like do you a lot of very interesting and complicated things. And I'm wondering, you probably also get a lot of applications to join your team. Either as post docs or postbacs or potentially even tenured scientists or tenure-track scientists. So what do you look for in people who want to come and interview to join your group?

>> Yes, that's a great question. I usually think that--I know I'm not the smartest person. I don't look for genius. I look for someone that's incredibly passionate and never gives up. That's sort of one of the rules of success that I always try to tell people. I knew I was never smart enough, and I some days still can't believe that I'm here doing science and I'm in charge. I just remember my faculty professors at the time, and I was so intimidated, and I sometimes still can't believe I am where I am. So it wasn't because I thought I was extra smart or all that, but when I'm told I'm not good enough, I always try to prove people wrong. I never give up. So that's the thing I look for is--you have to have an insane passion because life is long and hard. If you don't enjoy what you're doing, then it's going to be hard to keep doing it. So it takes a commitment, a passion. And for me it's quite easy to get people excited about the brain, right? I often feel other organ systems aren't quite as flashy so.

>> Yeah.

>> So when I'm talking to students, the brain is something that everyone's fascinated. So usually people interested is not too difficult, but I'm looking for people who are really committed and passionate. And, you know, science is not easy. It's very competitive. Long hours. And, you know, it just takes the right kind of person that is willing to take risks, that takes failure well, to get back up on the horse. If you give up and go away, you're not going to be able to do it. So those are kind of the basic properties, is, you know, the desire to do something really big, have fun doing it — I really think it's important to have fun to do it — and when the hurdles come — because it's not a matter of if, but when — and when the hurdles come, when the papers get rejected, what is your tendency then? What kind of person are you? Is it to try to make it better and succeed eventually? That kind of thing I would think I look at. And what kind of work they've done. All those things are important. What kind of training you've done. But to get past what you're sort of saying, rather than just a CV, when I start looking at people, those are the kind of things I'm particularly looking for. Independent creativity. I don't really like to tell people what to do. When people come to my lab, I ask them what would they like to do in my lab? And I'm trying to train independent-thinking scientists, so I want them to guide their own project. I feel that they're more invested in that. So that's the kind of people I like — self-motivated people because I don't know what to do with lazy. I really don't know how to make someone want to succeed. I can't do that. So I hope, you know, that when they come to me, that they're motivated. And I hope that they come to me knowing what I do already because it's very easy. And that there's something about what I do that they want to learn. So for me those things should be taken care of. Then it's, okay, what do you want to do in the future? So then that's when I try to find out, again, how passionate they are. When they come up a roadblock, what do they do then? And never give up because that's the one rule, you just can't give up.

>> So if you had to stop doing science today, would you be satisfied or--?

>> No.

>> Is there something that you--what's your ultimate goal that you hope to reach before you stop doing science?

>> It's funny. I used to never let myself think about retiring. Because I thought I was sort of a failure. I thought I would die at the bench. I don't think that anymore. But I want to go out--I don't want to ever give up science because that's one thing clearly--the brain, use it or lose it. That's absolutely true. You know, I have to keep doing something. My wife would kill me if I just stayed at home every day too. Because, you know, I need something to keep me active and my mind active. So I never plan to just 100 percent retire. My most fun are interacting with the science that we do, but as you go further up the food chain, you spend less time doing that., so my vision for the future is to spend less time, you know, in charge of things and let other people do that because I firmly believe that I shouldn't do this forever. I would like to hand off to others. And then I basically spend less time managing or leading the department and more time just involved in science in my lab because that can be a little more interesting. But then, so past that, you know, I could teach because we don't really do much teaching here. That's something that I could end up doing — teaching. I just--I love interacting with people that want to learn about the brain and neuroscience. So I could never just stop.

>> Yeah.

>> Because I'm not sure what I would do most of my time anyway. So that's--I think about it more — spending less time with administrative duties because that's not necessarily something that I strive for. Others do, and that's great. Just spend more time doing just science. Step down from leadership kind of thing. Do just science because that's more fun, to feel competitive. And there's still challenges, but that's more fun. And spend the last several years doing just that. And then after that, at some point, I'm not sure. There was a time when people, either you were a PI, and we get reviewed every four years and we had to have outstanding reviews or you had to retire, but NIH is starting to realize people like me, maybe, there's like a slow phase out. Maybe decrease the size of my lab slowly over time. You know, that kind of thing is a nice idea. You know, I have five postdocs now. You know, go in half and slowly phase out. That kind of thing might be good. And then I can control the rate at which I feel, you know, I could change my mind and accelerate or decelerate that. That's something that I think sounds pretty good, is slowly go into the sunset.

>> Yeah. Well, we are very close to being out of time.

>> Okay.

>> So I want to make sure, is there anything that we didn't cover yet that you might have wanted to be sure that you communicated, or you were hoping that someone like me would ask you?

>> No, I'm pretty satisfied. I just, you know, I think science is a spectacular career. I really worry that the young people think it's too hard because a lot of people say it's harder and harder to get grants, so that really worries me that people aren't feeling like careers are great--science is a great career. By I just find that it's amazing, and I just hope that the young people, when they're coming through, they decide what's the most passionate that they're interested in. You know, because, again, life is long and hard. I think a lot of times people pick jobs for different and the wrong reasons. They should think long-term. And science is, has its difficulties and challenges, but I really think it's a spectacular career. There's a lot of travel, should you want to travel, that goes with it. You get to do new and exciting things. You get to write the textbooks, you know. You know, you get to put the information in the textbooks. You get in events. New knowledge. And discover new things that nobody else knows. For me that's a reason to work hard every day. It's a great career and a calling and I just wish — hope — that the young people keep to that and don't think of the immediate return on a career and think of long-term and society and that. Because as we live longer, diseases like Alzheimer's and neurodegenerative diseases in general are going to impact more and more of us, so we really need smart people to keep at it to understand the circuits and how they work and how to fix them when they go awry.

>> Do you think we're eventually going to be able to fix pretty much everything in the brain?

>> Everything, never everything. Because as we even live longer, other things are going to--like you know, 200 years ago Alzheimer's and Parkinson's wasn't really too much of a problem because people didn't live that long. So, you know, as you live longer and longer, at some point there may be an upper end limit, so other new things will come.

>> And since you can stick an electrode into a nerve cell and you can activate it, do you think people are going to merge with computers and machines at some point?

>> Yeah, I don't know. I know people are talking about AI and all that. I, myself, am not that interested in that kind of thing. I love the brain — the jelly part of the brain. There's no doubt in the future you could improve circuits in different ways. I, like I say, I really, I try not to think too far into the future on that. I'm not one of those theorist kind of types of people like that. You think about some of the robots if people have a disability, or if they have a spinal cord, you know, paraplegic or all that. Those kinds of suits. That might be really cool, that kind of thing. Some kind of mechanical aid in case of an injury or disability or neurodegenerative disease. So that kind of stuff is cool, so that may be the kind of thing you're talking about, but I'm sure the way humans are, we're going to go further and further. It's going to get crazy so.

>> Yeah. We're going to read each other's minds, but you're probably not too interested in doing that yourself.

>> Everybody, yeah, everybody would like to do that. I'm not sure you really want to know what people are thinking so.

>> Nope. Cool. Well, I really appreciate your time.

>> I appreciate your time. Thank you so much. I really enjoyed this.

>> Yeah, me too. Hopefully we get to do it again sometime.

>> Sure, any time. I'm here.