Sam Wang is an associate professor, Department of Molecular Biology and the Princeton Neuroscience Institute.
Wang grew up in California and studied physics at the California Institute of Technology. Seeking his Ph.D. at Stanford University, he switched to neuroscience. He has worked at Duke University as a postdoctoral fellow and aided political leaders as a Congressional Science Fellow. After completing his postdoctoral studies, he spent two years at Bell Laboratories in Murray Hill, N.J., where he learned to use pulsed lasers to study brain signaling before coming to Princeton.
Wang, who has published more than 40 articles on the brain in leading scientific journals. His educational reach extends past the laboratory and classroom in his books, popular articles and efforts to convey neuroscience to interested nonscientists.
Question: What is neuroplasticity?
Sam Wang: Well, people have known that experience can change the brain ever since it became known that the brain was the seat of consciousness, thought, and experience. And so, I would say that for hundreds of years, it’s been known implicitly that the brain must undergo change because, of course, if the brain is the physical object by which we generate our consciousness and ourselves, then there must be some physical change happening in the brain.
So in that sense, I think neuroplasticity has been known implicitly for centuries. But I think it’s really been in the last few decades become really appreciated exactly what happens in the brain. So about a little over 50 years ago, a Canadian psychologist named Donald Hebb suggested the specific idea that experience could change the brain in ways that perhaps there’ll be some pathway that gets activated in an order of events that gets turned on when we experience something and then, when we recall it, we are, perhaps, playing it back, and have suggested that. Before him, the pioneering psychologist William James suggested it.
And you can even find the suggestions of this in writings of Thomas Hobbes and even Aristotle. So it’s been in the last 50 years or so that this suggestion that’s been around for a millennia has turned into a very concrete suggestion about neural pathways. So that’s neuroplasticity in the adult brain. Then, there’s also neuroplasticity in response to injury and also during development. And all these things are facets that have been studied facets of neuroscience that have been studied over the last few decades and it’s becoming really appreciated how much the brain can change.
Question: Is stress good for the brain?
Sam Wang: Well, certainly… When challenged, we can do more and everyone knows this. In the absence of challenges, we don’t necessarily reach our full potential. Now, I don’t know that that necessarily means that stress per se is good for the brain. What I mean by stress is very specifically secretion of steroid hormones. These hormones that turn up when we are under some low-level pressure, when we’re not allowed to sleep or when we’re under some kind of bodily stress where we are put into some kind of adverse condition for long periods of time.
Certainly, pressure can make us perform better but chronic stress… It has been demonstrated to slow down the birth of new neurons, to reduce the plasticity of dendrites. And so, there are physical consequences of chronic exposure to stress hormones. And those long-term effects of stress are mostly unlikely to be very good for us.
Question: Does brain food work?
Sam Wang: I have, on my desk, a bottle of pills that I picked up in Chinatown once, that are called brain0enhancer pills. And I keep that sort of thing around, sometimes, my office as basically a joke. A lot of these supplements have no demonstrated positive effects on brain function. And that includes ginkgo biloba and includes other supplements that you can take. That’s one problem. Another problem, of course, is these supplements aren’t controlled for what’s in them.
And so, as a result, if you buy something like, let’s say, St. John’s Wort, there’s tremendous variation in what you’re getting when you buy those things. So even the claimed pharmacological agent that’s in them maybe present in highly variable quantities. And it’s something that we would never accept in some FDA approved drug.
The rule of thumb for foods that maybe good for the brain is that things that are good for your heart are good for your brain. So it’s, again, this principle of good for your heart, good for your brain. And examples of that include green, leafy vegetables. They include not having too much in a way of saturated fats because that improves your circulation when you get older.
And your brain lives off of oxygen in the blood and so you need blood. And so, when your heart is not getting the oxygen, your brain is not getting the oxygen. One category of foods that seem to be somewhat helpful is antioxidants. So, for instance, blueberries, especially wild blueberries, have antioxidant properties and they seem to have some kind of protective effect, cognitive function as we get older.
There is evidence that omega-3 fatty acids are good for both the heart and for the brain. And, in fact, I, myself, take omega-3 fatty acids. Of all these things, you can take. Just to put into perspective, the only things that I make a point of eating are those and blueberries. I like blueberries.
Question: Does art therapy work?
Sam Wang: Well, I’ll be honest. I don’t really know a lot about demonstrated effects of these therapies like art therapy and music therapy on the brain. I think one major mechanism that is worth thinking about is the idea that these therapies reduce stress. One thing that has been demonstrated is that stress hormones are bad for the brain.
So, for instance, sleep deprivation leads to the secretion of stress hormones, being in danger. Stress hormones arouse and the stress response arouse evolutionarily to be something that works briefly. If there’s danger or if there’s something that’s caught your attention and you need to get away from it, the idea is that your certain systems in your body shut down like your immune response. And the idea is that you got to shut down the unnecessary things so you can get away from danger quickly. So that’s the normal biological evolutionary history of stress hormones. But now, on modern times, we have situations in which stress is always present.
And so, one major way that these therapies may work is by simply reducing the secretion of stress hormones, which is good for the brain. Stress hormones, when chronically present, can damage the brain.
Question: Does physical exercise improve the brain?
Sam Wang: It’s not fully understood what it is that exercise does that’s good for the brain. The empirical observation is that the… one of the best things you can do to keep your brain alive and healthy is fitness training, things that get your heart rate up, the kinds of things you hear about, getting on the treadmill for 3 times a week for at least 20 minutes in each session. That’s a classic way of getting fitness training. And that’s been demonstrated to improve brain function especially in older people. The mechanism is not known.
Here are the two major candidates.
One candidate is simply improving blood flow to the brain. And, again, it’s back to the heart-brain principle, things that are good for your heart are good for the brain.
Another major mechanism that’s been suggested is the secretion of a signaling molecule whose job it is to allow dendrites to grow and to be plastic. And this gets back to what we were talking about before, about neuroplasticity. This molecule is called brain-derived neurotrophic factor. And if you know what a neurotrophic factor, you know from the name what this does. It’s a factor that’s made in the brain that causes neurons to grow. It’s a trophic factor. And that factor has been demonstrated to improve plasticity in dendrites. And one hypothesis that people are investigating is the idea that exercise; by triggering the secretion of BDNF, this neurotrophic factor, may lead to increase plasticity and improve brain function.
Question: Will sex drugs change the brain?
Sam Wang: Well, that’s an interesting question. Because existing drugs like the ones that you mentioned are all about the plumbing and the mechanics of--especially in men of sexual performance. Something that cuts to the heart of who we are as loving or sexual beings is the feeling of love. And that’s a whole other category.
And major singling molecules in this category are molecules such as oxytocin and argenin-vasopressin. Oxytocin and vasopressin are secreted when we feel feelings of romantic love. They’re also secreted when we feel feelings of love towards a child. So, for instance, mothers, when they hear their baby cry, will feel their milk drop and the mechanism of that is the secretion of these molecules to cause milk to be secreted.
And so, it’s possible to reproduce feelings like that. Those same singling molecules are also important in generating a feeling of trust. So, for instance, people who take oxytocin in the form of a nasal spray exert more… express more trust when playing some negotiating game with somebody. And so, now, we’re talking about molecules that can affect our emotional responses to other people. And that seems to cut somewhere to the heart of what it means to be loving or sexual.
Question: How effective is meditation?
Sam Wang: Well, there’s a subjective report that meditators [report], right, feelings of peace, being able to focus.
There are many versions of meditation. And the version meditation people practice leads to different affects. So, for instance, Buddhists report a particular state of objectless compassion, so feeling compassion without any specific object, without a person as the target. One thing that’s been observed experimentally is that when you put people into a brain scanner and look to see what happens in their brains, it’s possible to measure a very large electrical oscillations in the brains of, say, Carmelite nuns experiencing mystical union with God or experienced Buddhist practitioners entering this objectless compassion state. And what’s observed is that you can see these oscillations, which basically are the result of neurons being active and synch with one another and being active more or less in cycle with one another.
Buddhist monks can achieve an oscillation of that in what’s called the gamma frequency bound that’s only found in non-expert meditators when they’re having seizures. Okay. So these people can do something extreme with their brains.
And I’m not sure that it reveals anything about the nature of reaching enlightenment or the benefits of meditation but, I think, one thing is very interesting about it is finding a neural signature that shows exactly which parts of the brain maybe trained when people learned to be very good at these things. And I think that, scientifically, that’s a rich source of questions for investigation.
Recorded April 24, 2009