Wisconsin Public Television University Place  The Neuroscience of Addiction Brenda del Moral  4/19/13 UP862 cc >> Hi everybody, and welcome to Edgewood College. My name is Brenda del Moral and I am an assistant professor in biology in the department of biological sciences, and in the school of arts and sciences. Edgewood College is a liberal arts college in Madison, Wisconsin. This is our first filming here at Edgewood College. Hopefully they'll be many more to come. I'm really excited today to talk to you about my talk which is the neuroscience of addiction. I'm going to take this a systems approach, so my hope is to bring you through a multi-leveled approach to the disease of addiction and how it effects the whole organism down to a molecular level. And even possibly bring you to the next generation. This is actually our college right here. This is the Sonderegger building where I spend a lot of my time. 

When scientists, myself included, start thinking about how an addiction is defined as a disease one of the important things is to frame what addiction is and what addiction isn't. There is still actually a lot of inaccurate perception among the public about addiction as a disease. This is actually a disease that effects about 22.1 million Americans. This was an estimate that was recently done in 2011.  And when we talk about addiction it's actual diagnosis. It's based on something called the Statistical Manual of Mental Disorders. It's commonly referred to as the DSM-IV. What this means is that approximately three of these criteria need to be met within a year in order for a person to be diagnosed as a person with the disease of addiction. I'm going to use my mouse to point, and hopefully you can follow that on the screen. Here are some of the characteristics that must be met. 

Tolerance, needing to use more of a drug in order to get the same effect. Also, withdrawal symptoms, taking more of the drug on a regular basis. Then also, what is perhaps a bit more interesting to me, are these lower criteria, a persistent desire to use more drugs, spending more time getting drugs or working to get drugs and taking the drugs, and perhaps most interesting, is continuing to use these drugs despite negative social consequences. These can be consequences in the work place, among family, friends, etc. Or legal consequences. It's this one, this last criteria that's most commonly used in scientific literature as really being the hallmark for the disease of addiction. This is one of the most important criteria that are considered. What really changed public perception and was a really big shift, if you will, in how addiction was viewed, was this article that came out in 1997 by the former head of the National Institute of Drug Abuse. That's often called NIDA. NIDA is one of the funding institutes under the National Institute of Health. 

At the time it came out Alan Leshner said, addiction is a brain disease. He wrote about this in an article titled the same thing. That was really a shift from the ideas that had been previously been generated about addiction, as more of a problem of a person's willpower, or just simply an inability or an unwillingness to stop using drugs. This shifted it more into an actual physiological disease much like we would view a disease in other parts of the body, for example. He described that in this part right here where he talks about the good, the bad and the ugly. Part of the criteria that he used to demonstrate that addiction is a brain disease is that we know some things about addiction now, and we understand some of its physiological processes. For example, the brain circuits, we know the areas of the brain that are involved in mediating, or in facilitating behaviors of drug addiction and physical dependence. We know some of the proteins that are involved, what we call receptors. We know some of the changes in the neurochemistry or the chemicals that change as a result of drug use. And we know the overall activity of these areas of the brain. 

So we have some idea that addiction really is a change in the physiology and the structure of the brain in certain discrete areas. That lends some credence to the idea that it's a disease. It's not simply a problem of will power, if you will. But there is the down side. Part of it, when he talks about the bad, is this part right here, public perception of the disease of addiction. You know, this was a great shift, if you will, in how addiction was though about. Also, as science comes out with more and more information about what addiction is and what are some of the problems, and potentially what are some of the treatments, it's hard to put this in practice in the clinic. Translating what occurs in the scientific literature into the clinical and practical application of the literature in treatment facilities or in the clinic is difficult. Then there's still some old biases that may persist in treatment facilities. Oh, I know this worked in the past, and it's worked for a great number of people, so I'm going to keep doing this even though it's been suggested by science that it's not particularly helpful, or doesn't give any proven result. 

Then there is the really ugly side of addiction which is what's listed here. Societal stigma continues to be a big problem, especially with the aspects of its links to criminality. Often times mental illness is co-morbid, or it's diagnosed at the same time as disease of addiction. So a person might be suffering from more than one disease that is linked to mental health. Also, that these changes that occur from using drugs, and some of which we'll show today, are drug changes, changes caused by the drug use, that persist throughout the entire time of a persons use and even after they have stopped using drugs and they go into a period of abstinence where there's no drug use. These changes in the brain still persist. It's not just that it ends once the drug use ends. These changes that are still there continue to persist which makes the last point, being prone to relapse a particular problem. If we think of the circuitry of the brain, the connections between different parts of the brain, being hard-wired, then that becomes difficult to change within a short period of time that abstinence may be occurring. This was actually a really pivotal time for thinking about the disease of addiction. 

So when I talk about it, and we talk about it in scientific literature, what we're really talking about addiction as a chronic brain disease. In some cases, even a developmental disease, if you will. It also has effects that escalate over time, a person continues to use despite negative consequences, sometimes very severe negative consequences, making addiction a particularly cunning disease. It's difficult to treat. Then also, a person is prone to relapse. If we think about addiction as a disease and in phases of time, we can think of it as three periods, if we just loosely divide it up. There's the initial drug use and drug use exposure. This is the initial period of drug addiction. This is where a person might be experimenting, or just initially using drugs, but has not yet met the three criteria necessary for a diagnosis, but then progresses into that phase where you see the compulsive behaviors that are illicited by drug addiction as well as some of the other criminal behaviors that can also occur that make the getting of the drugs and the using of the drugs foremost on the addict's mind. Then there can come a period of extinction or abstinence where a person's no longer using the drug, and even despite many months, sometimes years, of abstinence a person can continue to relapse. 

We can think of it in these three phases. What I'll largely be talking to you about today is this very first one, this initial stage. What really intrigues me and interests me is what happens when a person starts using drugs or even starts learning a process that makes it stamped in the brain, so to speak. How do we get to that point? That's really the part that intrigues me the most. When we think about addiction we're thinking about it as an actual disease and not just simply a series of physical withdrawal symptoms. For example, we can be physically tolerant of certain chemicals and experience withdrawal symptoms from them, but that doesn't necessarily mean that they are under the umbrella of addiction. For example, I drink a lot of coffee. I'm well known for drinking a lot of coffee. I feel like I'm always defending coffee. Coffee does have, in fact-- you can build up a tolerance. 

I know that I myself have a mild physical dependence on coffee. But yet, even with it's withdrawal symptoms, the withdrawal symptoms aren't sufficient that I will go out and cause a long host of negative consequences for myself in order to get more coffee. I will have a headache. As an indication of this, I put up a picture of the late Amy Winehouse. Here she is on this side drinking a cup of joe, a good, old fashioned cup of coffee. She looks healthy. She's present. She's alert. She's awake. This is Amy Winehouse after a long night of drug use and alcohol and drug abuse. 

You can see a clear distinction. When we talk about addiction it's more than just a physical withdrawal symptoms. It's a disease that persists even in the absence of the drugs. When I, and many others, think about addiction what I think of addiction as is a disease that takes normal learning about natural rewards-- natural rewards being things like sugar or food, sex, social interactions, things that are normally reinforcing, and hijacking the brain so that that becomes the most important thing. The pathway in the brain that is solidified or cemented, and that keeps getting reinforced over and over at the expense of other natural rewards. And quite frankly, other types of learning.  I want to take you through what I call a systems approach to the disease of addiction. For each one of these steps I'm going to give at least one graph or set of data that illustrates the point the addiction is not just a disease of behavior. Although behavior is most prominently what we see, especially as family members, or the public or employers. It actually is integrated-- Excuse me. 

Addiction is a disease that is integrated not just in the behavior, but also within a specific pathway in the brain. We'll talk about that more. Addiction even goes beyond that. It's not just within a specific area, but we can bring it down to the cells within that area of the brain. The cells within those areas of the brain we call neurons. Those are the nerve cells. If we stop at the neuron our story is still not complete. There are changes that occur within the neuron that can activate or silence genes that will reiterate, or reinforce, this learning process in addiction. I'll even take it a step further and say that perhaps it's not just this. We might even be able to pass some of these traits on to the next generation. 

That's an equally interesting and potentially terrifying thought. Science is starting to really unfold some interesting things about this as well. We'll start with, what do I mean by the learning process. There are several schools of thought on learning. When I'm talking about the type of learning that I'll be showing you, I'm talking about the process of reinforcement. This is where there is some kind of stimulus that is present. In this case here, we have a hungry rat. Hunger can be a very powerful source of motivation. What is reinforced for this rat is to go out into its environment. He's very hungry so he's going to go out and explore the environment in search of food. 

He finds these garbage cans and within the garbage can is an apple. Here is a picture of the rats eating the apple. Going out and searching for the food, that behavior is reinforced by the reinforcer of the food itself. We could also, if we wanted to think about this as a human corelet, if you will. We can think about this as a teenager or a young person, who are particularly vulnerable when it comes to the disease of addiction. We can think of a teenager who is stressed or isolated or having some kind of what we might term as a negative emotional response, feeling really down, who goes out to search his or her environment at school. Perhaps they're talking about this to somebody else and they say, oh, you know what I do when I don't feel well. It becomes an encounter with drugs. In this case there's a picture showing a student purchasing the drugs. The young person takes the drugs and feels different. 

They feel, sometimes, better. They feel distant from whatever was causing them anguish in the first place, but in some way that response is reinforced by feeling better about the situation or the initial stimulus. We approach this learning process-- This is one of the learning processes that can become hijacked or focused on when we think about the disease of addiction. In order to talk about this on a systems level I need to introduce some parts of the cells of the brain, the neurons, and how they communicate with one another. Because this becomes really important for the circuitry within the brain. We have a picture over here of a neuron. This neuron can be thought of as a typical neuron in the brain that sends and receives signals. Neurons are critically important because they're the communicators of the brain. These are the cells that are communicating across the areas of the brain at are involved in any process, but certainly learning and certainly addiction. If we look at the top here, this part right here is the cell body and there are these projections out. 

These projects can branch out like a tree, hence they're called dendrites. If we think of a neuron as sending and receiving signals, this is the end right here that receives the signal. This is the receiving end. Then there is the axon that projects down like this and makes a contact onto some other neuron. This axon right here is the sending part of the neuron. This is what is communicating the cell that was received in the cell body to some other cell. What is also sometimes really easy to think of is to think of the receiving end, these dendrites, as just being these flat, well, flat surface, much like is shown right here. But actually if we look, is we use a powerful enough microscope to look at the dendrites themselves we can see a few that are much more like this picture here. This picture shows you branches off the dendrite. Then you can see these small areas right here. 

These areas are projection off of the dendrites themselves. These projects of the dendrites are called spines. The spines are actually really important because these are critical for integrating information that others neurons send to that nerve cell. These spines can be present all throughout. What they really do is they increase surface area and they increase the likelihood, or the opportunity perhaps, of neurons communicating with one another. The point of this is integration. It's really easy to think of neurons in the brain as one neuron communicating with another neuron, that communicates with another neuron. But that's actually not true. Really, learning is about modulating all of these inputs onto a neuron itself. It's not necessarily a one to one ratio. 

There can be integration, and in fact, we find this is exactly what happens in learning. It will be multiple processes from many different neurons all projecting onto one neuron itself. It's not a one to one ratio. It can be many neurons projecting and making a contact onto just one neuron. This contact of one neuron to another we call a synapse. Those are some of the ways that integration can occur. Integration is really a cellular way to communicate between one cell and another. In fact, we talk about learning as an integration of what's learned. It's really honing in and modifying these neural connections that becomes really important. In fact, in the case of addiction they become so hard-wired that things that commonly don't seem to be affiliated with anything in particular, like a mirror, for example. 

That's just something that we use to get ready in the morning. For somebody that uses a psychostimulant like cocaine, it can have an entirely different meaning, because if it's intensive use always correlated with the same thing, which is using as it a platform for using drugs.  One common misconception about learning is about how the brain is actually connected. When I'm talking about that connection I'm talking about one neuron communicating with other neurons. I think of this often, I think of how students learn and how to best communicate to how students learn. We often think of young people, especially, as sponges or open books. They're just waiting to suck up all this information. They don't necessarily have a long list of previous experiences. That's true to a certain extent, but that's not the entire picture. This is an MRI scan of the amount of gray matter, gray matter meaning the areas where these neurons are present, in a five year old child. 

That is shown right here. Then as that child increases in age. If you look at the scale over here you can see that the pink and the red areas are the greatest amount of gray matter. At the bottom are the blues and the purples. You can see that these are areas of a lot of gray matter, the highest amount. It's not an increase learning over a period of time. I think it's safe to say that you learn from the ages of five to 20. You're learning things all the time. What's not happening is that there's an increase necessarily in your old connectivity or the amount of neurons. What's actually happening is that you are loosing neural connections, and the amount of cells that can make connections because, as this child is learning, they are honing in and focusing the circuits and reinforcing these specific connections. 

The amount of gray matter doesn't increase as we learn, and not necessarily does the neural connectivity or the number of connections increase, but they become solidified and reinforced. They are enhancing our learned knowledge. As you can see, over time, there is a significant decrease in the amount of gray matter at 20. Although this area right here I would like to point out. At the age of 20, these are the frontal cortices. Especially we know within the pre-frontal cortex, this area is not solidified. It's not fully developed by the age of 20. That actually occurs about age 20, 25. What this is also showing, right here, this is an age of incidence for first drug use. It shows the extent, or the frequency, with which the first drug use occurs. 

For children or infants it's very small. Sometimes one or two first drug occurrences occur as a child. But the most common time when the first drug occurrence occurs within a person's life span is when they a teenager or adolescent. If we think about the adolescent and teenage years as approximately 11 to 19, approximately, and we map it over here to this approximate time, we're talking about these areas right in here, these timelines. You can see, they're still a lot of development that is occurring and that early exposure to drugs, because there isn't a lot of learning that's already occurred, makes a young person more vulnerable to becoming an addict than perhaps a person who is first using drugs later in life. We know this to be true. There's been a strong correlation established by the National Institute of Health. So when we talk about the parts of the brain that are involved we're actually talking about something that we call commonly the mesolimbic dopamine reward pathway. I'm just going to call it the reward pathway. That's quite the mouthful. 

What we're talking about are mid-brain areas which release a chemical that is often talked about in addiction studies. That chemical is called dopamine. This is a chemical, or a neurotransmitter, that neurons use to communicate to one another. It's these areas right in here. Then also these striatal areas right here as they project forward to these frontal cortices areas. It's these pathways right here that we call, collectively, part of the reward pathway. When I talk about areas of the brain that are involved in learning, addiction, the pleasurable feelings of drugs that can induce euphoria, motivation, it's these area of the brain that I'm really talking about. It's these area that have been isolated as part of the important process for developing the disease of addiction. So if what I showed you previously is true that the number of neural connections and the number of neurons over time may decrease as learning is happening, that a singular pathway or a set of pathways becomes reinforced, we actually have some data to suggest this. This here is a graph that is taken from a rat. 

This set group of rats have exposed to an injection of saline which we wouldn't expect any effect from. These have been injected with amphetamine, also commonly known as speed. These are all of the spines that are present on one of the dendrites in a saline injected animal, i.e. a control. These are after the drug has been injected. This is just one time. But you can see what's happened. At least I hope you can see, that the density, or the number of spines, has significantly increased. In fact, if we look at this graphically we can compare the saline treated and we can see that there's a much higher number of spines in the amphetamine treated. What's actually happening is the number of neural connections, connections between neurons, the potential for that is increasing because the number of spines are increasing. It's not just necessarily that the number of spines are increasing. 

This picture shows right here, this is in the control rat with one spine and some other projection onto it. This is in the amphetamine treated. There will actually be a growth of the spines in response to the drug treatment to reinforce those pathways. Drugs structurally change the brain. And this is just in the initial beginning. With continued drug use,  especially of the same type, these pathways can have an even greater growth of spines and can respond even more strongly, and at the exclusion of other things, in the disease of addiction. If we think of addiction as, in some ways, learning being hijacked by the brain, we can think of this as a model right here. Here is a normal brain undergoing normal life experiences, whatever normal is, but non-drug included set of experiences. It has lots of activity. It has lots of neural connectivity. 

This person is able to learn things all the time. We can think of this as a model for the addict brain where these reward pathways that are heavily reinforced and it's at the expense of other activity. There's a decrease in activity in other parts of the brain, but the parts that are involved with the reward pathway become heavily wired. When we talk about how drugs enact their effect in the brain what we're talking about is a series of chemical changes, a series of protein changes. That can occur over a period of time. Again, if we take this picture right here, this is the receiving end. This is the plasma membrane of a spine of one of the neurons. This is the end that sends the signal right here. This is the very end of the axon called the axon terminal. This will release a chemical like a neurotransmitter into this space right here where it can then bind to these proteins that are embedded in the plasma membrane called receptors. 

These receptors are specific for a certain chemical. In this case, these are dopamine receptors that are specific to bind only to the chemical of dopamine. This is a normal neurotransmission process that occurs in everybody's brain. What you can see here is when the chemical is released, dopamine, it can be present, these stars, bind to the different protein receptors on the receiving neuron. Or it can bind to what are called dopamine transporters. These transporters will actually bring the dopamine back into the nerve, to the axon terminal, to recycle it. It can be used over and over again. What happens with drugs of abuse like cocaine, is that cocaine, when a person in exposed, binds to this dopamine transporter and it blocks it. This dopamine transporter can no longer go back into the presynaptic terminal. It can no longer go back to the sending end of the neuron. 

What happens then is that all the dopamine is left in that space, and it can keep binding to receptors and keep binding to receptors, and continually keep activating these spines. So drugs of abuse, like cocaine and other psychostimulates, can not only effect the protein receptors, but they can also effect the transporters. And these effects can be very long-lasting. As I said before, there's initial changes that happen by different drugs of abuse. This is a technique that actually, if we go back to this picture. This space right here? A probe can be inserted into a specific areas of the brain and it can actually measure the amount of dopamine that's present in that extra-cellular space, the space outside of the cells. That process is called in vivo microdialysis. In this experiment what happened is that animals where exposed to different drugs, in this case amphetamine, cocaine, nicotine and morphine. This process of in vivo microdialysis was used to measure the amount of dopamine that's actually present in the extra-cellular space, in the space between two neurons. As you can see here, this is dopamine. 

You can see, after amphetamine it rises very sharply, and then it decreases. It actually increases ten-fold above baseline, above regular dopamine release. In cocaine you can see that again it elevates and comes back down. You see this trend also for morphine and also for nicotine. Nicotine not quite as high, but still present. This is with a single injection of the drug, or a single exposure to the drug. It greatly elevates the dopamine that is present between the cells to keep activating these neurons over and over again. It can be a ten-fold increase. It can be a four-fold increase, but it's many times over increasing the neuron transmitters that are available, i.e. the activation of the cell. Drugs can effect the chemistry. 

They can also effect these transporters. This is what's called a functional MRI scan. These are scanned images looking at this dopamine transporter which is the protein that carries the dopamine back into the cell to be recycled. This is done looking at the dopamine transporter activity within this middle area of the brain, part of the reward pathway. This is in a normal control person. This is in a person who has not used drug. You can see that it's highly active. You can compare it to the scale here. You can see a very high amount of activation. If we look at a person who was a chronic methamphetamine user who has been abstinent and not used the methamphetamine or any other drug for at least one month, you can see that despite the period of abstinence there's still not as much activity in this area in the brain as a normal control person, a person who doesn't use drugs. 

Only after 14 months of abstinence do we only start to see a return to the normal amount activity in the brain. So 14 months of abstinence is over a year of not using the drugs, and these changes to just this protein alone are still present and they're still persisting. So despite not having the drug in the addict's system, these neural changes continue to be present within the brain. This could potentially set up a person to be more likely to relapse and start using the drugs again. If we look at protein transporters we can also look at receptors. We can model the normal learning that occurs that gets hijacked in the disease of addiction. We can use chambers like this that is shown with the rat in the center. This is called operant learning. This is the type of learning that was discovered and coined by B.F. Skinner where you place the rat into what is called an operant chamber, or a Skinner chamber, depending on who you talk to. You can bring the rat inside and this lever can extend out. 

As you place the rat in initially the rat will go around exploring their environment, which is normal adaptive behavior. Maybe it'll accidentally hit, or intentionally hit this lever. What can happen is that a food pellet, and in the next case-- excuse me. In the next example that I'm going to give, sugar pellets, because rats love sugar. This pellet can actually be dispensed down into this food trough. The rat can then go an retrieve the sugar pellet. We can automate and record the number of times that the lever is pressed and the number of time that the rat goes to get the sugar. Quite frankly, rats are willing to work for sugar quite a large amount when they are hungry. We're still using the motivation of hunger as the initial stimulus. This is as example of an albino rat that we use in our studies called --. 

This rat is in the chamber. Here are the levers that can extend out. They're not extended at this point. They're retracted. But when the session begins these levers will come out and the rat can press them. Every press that it gives it receives a sugar pellet in the trough. Then he can go enjoy his sugar pellet, then press and go and enjoy a sugar pellet. And do this many times over. We can use this in multiple ways to study different points in the phases of addiction. What I'm most interested in learning is what areas of the brain, and which proteins the different cells of those areas of the brain guide, or are critical, for the rat learning about how pressing the lever is reinforced by getting the sugar pellet. 

How it learns this operant behavior. Every time it operates the lever, it gets the sugar pellet. How is that learning, or where is that learning, held within the brain? We can do studies that look at this. In this case we can use a rat's willingness to press a lever for food. We can look at the very beginning, or the acquisition, of this behavior. We can put the rat into the chamber and the rat can start exploring the environment, and start learning that every time he presses the lever he received a sugar pellet as a reinforcer. In order to find which areas of the brain, and which protein receptors are important for receiving the signal of the neurotransmitter, what we can do is we can use a drug and inject it into a very specific part of the brain, parts of the brain that are in that reward pathway. We can then use a drug that blocks these receptors. These Xs are representing the blockade of these receptors. If these receptors in a specific part of the brain are involved in mediating this behavior, than rats injected with this drug in the mesolimbic reward pathway will not learn the behavior like their control counterparts. 

As we look at the very first sessions that occur, the first five sessions, where the rat is learning about the lever and learning to press the lever in order to receive the pellet. What we can see is these are the saline injected animals with the hollow white circles. These right here are the drug injected animals. These animals have received an injection that blocks a specific type of glutamate receptor. Glutamate is an important excitatory neurotransmitter in the brain. It's actually the most common one. This is in a part of the brain called the straitum. This is part of that reward pathway. What we find is that the number of lever presses initially doesn't have much significant different. But as a normal rat, who is not having any drug on-board, this group of rats learned to bar press. 

Now they're bar pressing approximately 150 times on average and getting quite a few sugar pellets. They'll continue to do this. We can see that before each one of these sessions the animals are injected either with saline or with the drug. These are the rats that are injected with the drug. They don't even get up to 50 times. Some of them are kind of learning that pressing the level leads to a sugar pellet. Others, not so much. In fact, once on this day, this dotted line indicates the day that the injection stopped. No longer did the rats receive any injects. The control rats are operating at about a standard level. 

Right here, you can see the white dots are all around 200 to 250 lever presses. And even after the drug is no longer in their system you can see that the rats that had that drug are still trying to catch up. They eventually do, but it took them longer, because they had this receptor in a specific part of the brain blocked. If we inject them one more time with the drug before putting them in the chamber, we can see no difference. That matters. What that means is that receptor, this type of glutamate receptor, in a specific part of the straitum, is critically important for learning this behavior but not carrying out the behavior once it's already been learned. It's only in that initial acquisition time that this receptor in this part of the brain is really important. This allows up to use a model of learning, that is a type of learning that all people do, and that gets hijacked in the disease of addiction, and investigate which proteins in which areas of the brain are responsible.  Of course, it would be a short story if we ended at just the receptors. As I like to always remind my students, there are lots of things that happen in the cells, besides the receptors, that are present that face the outside. 

This is representing a model of a cell which is shown right here. This is a receptor that is inserted into the membrane, the cell wall. When some kind of drug or neurotransmitter binds the receptor there are actually a whole slough of protein changes that occur. It's not like the signal gets to the cell. Something has to happen in order to change the activity of the cell. Actually, quite a few protein changes happen in order to change the signal in the cell. These proteins can even get into the nucleus and cause as activation, or an alteration, in the transcription of the DNA. DNA transcription is really important because the process eventually ends in the translation, or the production, of all of the proteins. These proteins are the receptors and the transporters. The DNA is transcribed and many more of the receptors are made available so that they can now receive the signal coming in because of the repeated drug use. 

This is a picture right here that gives you an idea of the number of molecules, this is an abbreviated list of the number of protein changes that occur once within the plasma membrane. Here are two ascending axon terminals. Here's the plasma membrane of a spine. And here are different receptors that are present within the cell wall. You can see the number of protein changes that can start to occur, and how these protein changes can get into the nucleus and actually cause a change in transcription of DNA. This is how the cell, when it receives a signal, actually causes a change in that cell activity. It's through this process. We have evidence that learning by itself, and also drugs of abuse, can alter gene translation. Excuse me, gene expression. This is a technique called in situ hybridization. 

What this does is it looks at gene expression taken from different slices through the rat brain, in this case. The process that I described before where the rats are put into the chamber and they learn to press the lever in order to receive the sugar pellet. This is the same technique that's trained here. In this case these are rats on the side, they have had no training. They didn't have the lever extended and they weren't able to learn the same process. These are slices showing gene expression of a gene called Homer 1A that are in the animals that have had the operate learning session, that have learned to press the lever for the reinforcer. These slices are taken from the rats that have just learned this process. After the fifth day where they're still in that early acquisition part, these are the representations from that day of learning. You can see, the blue is not indicating a significant activity, but you can see that expression is activated in these cortical areas here and are not when you compare them to the animals that didn't learn. So literally, learning changes the expression of what are called immediate early genes, the first genes to respond, like Homer 1A. 

It was named after the poet, not the cartoon character. If we look at the expression within these early learners we can see a lot of activity in this area right in here, and a lot of activity in this area as well. If we compare them to animals who have already learned this process many times over, the activity looks different. We don't see as much within this area, but we see a significant increase in this area. What this shows us is that normal learning can alter gene expression. These changes are getting into the nucleus and they are causing an activation of transcription. And they are leading to different types of proteins that are being made. This occurs in normal learning, and when this learning process gets hijacked, this process is even more heavily reinforced in the disease of addiction. What is probably three parts fascinating and one part pretty scary is the idea that what we do, not just that drugs can effect the behavior of the organism, and not just that it can effect the chemistry in different parts of the brain and can effect how these cells communicate to one another. It can even effect the proteins within the cell and change gene transcription in which proteins are actually going to be made. 

Then it's possible for these to be passed on to the next generation. Literally, what we consume, what we eat, what we smoke, any of these behaviors, might be possible to be passed on to the next generation. This is a growing field and a relatively new field of epigenetics. This Time article, I had to feature it because I felt like, in my mind, this is the first time that epigenetics was really put on a major public scale. It made the cover of Time! This was a story about generations of families. One generation of a family had a time when there was very little food available. If they looked at the offspring of the parents who had this really low intake of food and were essentially starving or close to starving most of the time, they found that the children of those parents lived significantly shorter lives. Then when they looked at that generation they found that through a reversal and eating excessively, that too, can effect the life span of the future children. They started to look at cross-generational studies. That's something that's pretty difficult to do in science and with case studies because this requires multigenerational time periods. 

When we talk about epigenetics what we're talking about is not changes to the actual genes themselves. This is not changing DNA. We're not talking about mutations. We're not talking about the X-Men. We're not talking about things that actually mutate the DNA. We're talking about the epigenome, which translates to above the genome. We're talking about chemicals that can turn off or on genes like a switch, like a light switch. They can actually, what's called "silence" genes. By chemicals binding to different parts of the DNA, or proteins affiliated with the DNA, this can effectively shut off certain genes. It's possible for these to be passed on through mitosis. 

If we take this picture right here we can see that this part right here is the double helix structure of DNA which we're really fond. It's the first thing that I think of when I think of DNA. I think of the double helix. If we look at this long string and we can see how it's wound around these proteins. These proteins are called histones. It actually gives this appearance, with the DNA that is literally wrapping around these proteins. This appearance is called beads on a string. Because that's actually the structure that it appears as. What happens is that before the process of mitosis the DNA is replicated, and it's also condensed. This area can be condensed further and further, all the way down, and get condensed into the form of a chromosome so that they can be copied, or split, if you will, into different cells. 

What can happen is two-fold. There can be chemical tags that can attach to the tails of the histone, which are extensions of the protein. These tags can effect how tightly the DNA is bound. That matters. If you look right here you can see that this is an activated gene. A gene is a certain sub-unit of DNA sequences that produces a heritable trait. Here's an activated gene that any proteins or chemicals would have access to. But when the proteins come together and are more tightly condensed because of these chemical markers, that gene is now in here. It's not assessable any longer. It effectively silences that gene, it's not allowed to now be transcribed. 

There are also methyl groups that can bind to the actual double helix itself, and also silence that part of the DNA sequence. This is a way that, without actually altering the structure of DNA, with these changes, parts of the genome can actually be silenced. That part can't be transcribed. These are temporary. These can be removed. These are chemical modifications, not an actual change to the genome itself. It is possible that they are heritable. I'm going to show you the next piece of data, a set of data from an experiment that suggests that this might be heritable and in mammals. I think it's the first study that actually showed this. This causes changes in gene expression, not to the genes themselves. 

This can be in response to any slough of environmental changes, both good and bad. They're not all bad. But certainly what we intake can effect future generations, or at least this is what this is suggesting. The first example of this was looking at changes that occur in mammals. This experiment was designed with two groups of mice. One group of mice was kept in a normal home cage and got to live out their happy, little lives in a normal home cage without any special enrichment or treatment. They're the control group. Another set of mice where exposed to what's called environmental enrichment. This is literally things like, toys are placed in the home cage and the mice get to play with the toys. They have exposure to an enriched environment above and beyond the typical home cage environment. 

This was done for this group of mice for six hours per day for 14 days. So, just for two weeks. Then they took that generation of mice, both the control group and the environmentally enriched group, and they bred them. They control group was bred with each other. The environmentally enriched group was bred with each other. Then they looked at the offspring of those mice who had no exposure to environmental enrichment whatsoever. They had the same home cage experience. It was the same among both groups. What they did with these mice is they looked at an area of the brain called the hippocampus. The hippocampus is where memories are stored. 

They looked at a common change in electrical activity that is really considered by most scientists as the pinnacle of learning within the hippocampus. This is a phenomenon called long-term potentiation. Long-term potentiation is when a really strong electrical stimulus is applied with an electrode into the hippocampus or another part of the brain, and that electrical stimulation, which is shown here abbreviated as theta burst stimulation. It's a series of electrical signals that are given in very quick succession. What happens is that the electrical activity of those neurons within the hippocampus change. Here they are at baseline. Here, this arrow, shows when the theta burst stimulation is given. What you can see is that there's an actually elevation, or potentiation, of the electrical activity. The electrical activity is no longer here. After the theta burst the electrical activity is potentiated above and beyond baseline activity. 

And it doesn't return back to normal. So it's not a quick spike up and then a return back to baseline. This potentiation actually persists over time. This is actually a hour later. What the different colors are showing is this black line is from the animals that were in the home cage. They did not receive the environmental enrichment. This is of the parent generation. You can see right here, this group right here actually has an enhancement of the potentiation. They have an enhanced long-term potentiation that persists. This is the group, in red, that was exposed to the environmental enrichment. 

So environmental enrichment can increase long-term potentiation within the hippocampus. It enhances plasticity, or changes, within the neurons within the hippocampus. That's really what we're saying. That's really interesting. What I find even more interesting is that these are the children of those two isolated groups. These are the offspring, not the children. Excuse me. They're the offspring of that generation. When we look at the offspring of that generation who had no environmental enrichment what we can see is that in the offspring of the parents who had no environmental enrichment, this is their potentiation levels. In the animals who had parents who were exposed to an enriched environment, they didn't, just the parents, we can find an enhancement of this potentiation. 

The environment has been the same for the offspring, but yet the parent exposure actually is changing the neural activity within the part of the brain important for memory. This is, in my mind, a pretty compelling case. Also, if we reflect upon the nature of addiction, a potentially very scary finding as well. Not without hope, what it does suggest is that the exposure, or the life and exposures of the parent, can be passed on to the offspring. This is compelling not just for people that have been exposed to drug use, but also for people who are abstinent. Perhaps some of the changes may not be solidified or passed on. Now this is not a for sure in human experimentation. This is looking at mice. But it is the first suggestion of heritable, inheritated, epigenetics changes in mammals. When we think about the learning that is involved in addiction and we look at it across this level, we can see that this is not just effecting the behavior, but it's effecting the whole organism, in most cases, the human. 

This is also looking at certain areas of the brain. Within those areas of the brain the cells are changed. The chemicals that the cells use to communicate are changed. The proteins inside the cell and on the cell membrane are altered. And these alterations can be long-lasting even in abstinence, and even possibly to the next generation. In my mind this is a pretty compelling set of evidence that suggests a multi-level, or a systems approach to the changes that addiction can have on the body. These changes are not short-lived. They're actually persistent, making treatment particularly difficult. If these neural changes still persist despite treatment, a person may still find it very difficult to maintain abstinence for any significant period of time. Their brain has not, literally, caught up to the changes in the lifestyle, or changes in exposure. 

If we think about modifying old messages, I remember these old commercials about, this is your brain and this is your brain on drugs. Remember these commercials? I have a very strong memory of these commercials. We can really think of it as modifying this. We can say, this is your brain, with lots of connections and a variety of neuron to neuron connections within the brain. We can think of, this is your brain on drugs. Not as many connections, but of the connections that persist, they're very active and they're very honed and specified. This creates a way of thinking about the disease of addiction as really a hijack of normal learning within the human brain. So I leave that with any questions. [applause]