This is your brain on meditation —

There's a feature worth reading in the New York Times today by John Hanc on the role that meditation plays in brain development, and scientific studies to explore "the extent to which meditation may affect neuroplasticity — the ability of the brain to make physiological change." — Xeni •

We've had a couple of posts recently about a hypothesis that links the current increase in obesity with an increase in easy access to foods that are designed to trigger reward systems in the human brain. Basically: Maybe we're getting fatter because our brains are seeking out the recurrent reward of food that makes us fat. Scientist Stephan Guyenet explained it all in more detail in a recent guest post.

It's an interesting—and increasingly popular—idea, though not without flaws. To give you some context on how scientists are talking about this, I linked you to a blog post by Scicurious, another scientist who wrote about some of the critiques of food reward and related ideas. In particular, Scicurious questioned some of the implicit connections being made here between body size and health, and eating patterns and body size.

She also talked about another critique, one which came up in a recent article in the journal Nature Reviews Neuroscience. If people are gaining weight because they're addicted to eating unhealthy foods, we ought to see some evidence of that in the way their brains respond to those foods. After all, brains respond to many physically addictive substances in special ways. But we don't see that with junk food. So does that invalidate the hypothesis?

Stephan Guyenet doesn't think it does. In a recent email to me, he explained that he thinks the food reward hypothesis is a bit more nuanced, and can't really be described as "food addiction". At least, not the same way that cigarettes or heroin are addictive.

Addiction is the dependence on a drug, or behavior, despite clear negative consequences. Drug addiction is associated with characteristic changes in the brain, particularly in regions that govern motivation and behavioral reinforcement (reward), which drive out-of-control drug seeking behaviors. Some researchers have proposed that common obesity is a type of “food addiction”, whereby drug addiction-like changes in the brain cause a loss of control over eating behavior. Hisham Ziauddeen and colleagues recently published an opinion piece in Nature Reviews Neuroscience reviewing the evidence related to this idea.

The review concluded that there is currently not enough evidence to treat obesity as a “food addiction”. I agree, and I doubt there ever will be enough evidence. However, this does not challenge the idea that food reward is involved in obesity, an idea I described in a review article in JCEM, on my blog (1, 2), and my recent Boing Boing piece.

The reward system is what motivates us to seek and consume food, and what motivates us to choose certain foods over others. To begin to appreciate its role in obesity, all we need is a common sense example.

Why do some people drink sweetened sodas between meals, rather than plain water? Is it because sodas quench thirst better than water? Is it because people are hungry and need the extra calories? If so, why not just eat a plain potato or a handful of unsalted nuts? The main reason people drink soda is that they enjoy it, plain and simple. They like the sweetness, they like the flavor, they like the feeling of carbonation on the tongue and the mild stimulation the caffeine provides. It’s the same reason people eat a thick slice of double chocolate cake even though they’re stuffed after a large meal. The reward system motivates you to seek the soda and cake, and the hedonic (pleasure) system encourages you to keep consuming it once you’ve begun.

But is this the same as addiction? If I took a person’s cola away, would they get the shakes? Would they break into a convenience store at night to get a cola fix? I’m going to say no.

I agree with Ziauddeen and colleagues that the evidence at this point is not sufficient to say that common obesity represents food addiction, and I appreciate their skeptical perspective on the matter. In obesity, as in leanness, the food reward system appears to be doing exactly what it evolved to do: seek out energy-dense, tasty food, and strongly suggest that you eat it. The problem is that we’re increasingly surrounded by easily accessible, cheap, commercial food that is designed to hit these circuits as hard as possible, with the goal of driving repeat purchase and consumption behaviors. Our brains are not malfunctioning; they’re reacting just as they’re supposed to around foods like this.

Snip from an essay in the New York Times today about the neuroscience of romantic love, by author Diane Ackerman:

While they were both in the psychology department of Stony Brook University, Bianca Acevedo and Arthur Aron scanned the brains of long-married couples who described themselves as still “madly in love.” Staring at a picture of a spouse lit up their reward centers as expected; the same happened with those newly in love (and also with cocaine users). But, in contrast to new sweethearts and cocaine addicts, long-married couples displayed calm in sites associated with fear and anxiety. Also, in the opiate-rich sites linked to pleasure and pain relief, and those affiliated with maternal love, the home fires glowed brightly.

The Brain on Love (NYT)

We recently hosted an article by scientist and guest blogger Stephan Guyenet that explained how certain foods—those with a high calorie density, fat, starch, sugar, salt, free glutamate (umami), certain textures (easily chewed, soft or crunchy, solid fat), certain flavors, an absence of bitterness, food variety, and drugs such as alcohol and caffeine—could trip reward systems in the human brain. Those reward systems, then, encourage people to eat more of the foods that trigger the reward. The result, says Guyenet, is a cycle that could be the link between the American obesity epidemic and the rise of highly processed convenience foods, designed specifically to trip those neural reward systems.

This theory, and several related theories, are increasingly popular in the scientific community. This week, there's an opinion piece in the journal Nature Reviews Neuroscience that looks at the strengths and weaknesses of these theories and talks about what research needs to be done going forward. It's kind of a space for researchers to step back and say, "Okay, here's what we know, here's what's not lining up with what we think we know, and here's what we have to do if we want to understand this better." In the context of science, an article like this isn't really a slam against the ideas it analyzes. Instead, it's meant to summarize the state of the science and share ideas that could either strengthen the case, or lead down entirely new roads.

Sadly, you can't read this article unless you have a subscription to Nature Reviews Neuroscience (or pay them $32 for single article access).

Luckily, Scicurious, a neuroscientist and an excellent blogger, has read the article, and has a nice run-down of what it's saying and what you should know. Some of the ideas being discussed here overlap with Stephan Guyenet's research. Some don't. But this is connected enough that I thought you guys would be interested in reading more and getting more perspectives on this issue. Let me make this clear, though: Guyenet isn't doing bad science. As with a lot of scientific research, there's often more than one way to look at the same data. Scientists can disagree without one person having to be all-wrong and another all-right. In fact, having different scientists working on the same subject is a key part of getting the facts right.

As you read, you'll notice that an important place where Scicurious' perspective really differs from Guyenet's is in terms of connecting the idea of "addiction" to certain foods back to the idea of an obesity epidemic.

...is there a place for food addiction? The authors think so, and I am inclined to agree. However, it needs to be much more stringent than the current model of food addiction that many people want to embrace (the idea that sugar makes you addicted or that being overweight means you have a problem). Changes need to be made.

First off, it's important to separate food addiction from obesity. Binge eating does not necessarily mean you are overweight, and being overweight does not necessarily mean that you binge eat. Ranking by BMI is not going to work.

Read Scicurious' full post.

(Via the illustrious Ed Yong. Image: Fabio Berti, Shutterstock)

[Video Link] BB pal Joe Sabia points us to this incredible video by Evan Shinners, Julliard-trained pianist and "best Bach player around." In the video, Shinners shows the world the colors he sees when he plays: he has synesthesia. You can follow him on Twitter, and check him out live on one of his upcoming tour dates.

Writing in Smithsonian magazine, magician Teller describes the neuroscience that underpins magical illusions, using admirably clear language to describe some of the weirdest ways that our brains can be made to fool us.

1. Exploit pattern recognition. I magically produce four silver dollars, one at a time, with the back of my hand toward you. Then I allow you to see the palm of my hand empty before a fifth coin appears. As Homo sapiens, you grasp the pattern, and take away the impression that I produced all five coins from a hand whose palm was empty.

2. Make the secret a lot more trouble than the trick seems worth. You will be fooled by a trick if it involves more time, money and practice than you (or any other sane onlooker) would be willing to invest. My partner, Penn, and I once produced 500 live cockroaches from a top hat on the desk of talk-show host David Letterman. To prepare this took weeks. We hired an entomologist who provided slow-moving, camera-friendly cockroaches (the kind from under your stove don’t hang around for close-ups) and taught us to pick the bugs up without screaming like preadolescent girls. Then we built a secret compartment out of foam-core (one of the few materials cockroaches can’t cling to) and worked out a devious routine for sneaking the compartment into the hat. More trouble than the trick was worth? To you, probably. But not to magicians.

3. It’s hard to think critically if you’re laughing. We often follow a secret move immediately with a joke. A viewer has only so much attention to give, and if he’s laughing, his mind is too busy with the joke to backtrack rationally.

4. Keep the trickery outside the frame. I take off my jacket and toss it aside. Then I reach into your pocket and pull out a tarantula. Getting rid of the jacket was just for my comfort, right? Not exactly. As I doffed the jacket, I copped the spider.

Teller Reveals His Secrets

The "flow state" is how neuroscience researchers describe that zone you can get into when you're doing something that you've become highly skilled at. It's a zen-like place in your brain — that state where you lose track of time doing something that you enjoy doing for its own sake, and where the job of doing the task seems to become something you don't even have to think about. You just do it, and you do it right.

The catch, of course, is that usually it takes a lot of heavy work to get to the point where the flow can take over. This is where Malcolm Gladwell's 10,000 hours of practice comes into play. But, over the years, scientists have learned that there are some ways around that 10,000-hour rule. Some people just seem to pick up on the flow easier than others, for instance.

If your brain isn't just naturally inclined toward the flow, though, there is the option of zapping it into line. This is called transcranial direct current stimulation—basically running a very small electric current through specific parts of the brain. In some studies, and for some tasks, it's been shown to induce a feeling very much like a flow state, and possibly make it easier for people to get to a high level of skill faster. Last spring, Pesco wrote about some of the research that's being conducted on this intriguing but still-not-proven technique. Recently, New Scientist reporter Sally Adee tried it out, and saw a significant short-term improvement in her ability to spot and hit targets in a video shooter game.

The mild electrical shock is meant to depolarise the neuronal membranes in the region, making the cells more excitable and responsive to inputs. Like many other neuroscientists working with tDCS, Weisend thinks this accelerates formation of new neural pathways during the time that someone practises a skill. The method he is using on me boosted the speed with which wannabe snipers could detect a threat by a factor of 2.3

It's not yet clear why some forms of tDCS should bring about the flow state. After all, if tDCS were solely about writing new memories, it would be hard to explain the improvement that manifests itself as soon as the current begins to flow.

One possibility is that the electrodes somehow reduce activity in the prefrontal cortex - the area used in critical thought, which Csikszentmihalyi had found to be muted during flow. Roy Hamilton, a neuroscientist at the University of Pennsylvania in Philadelphia, thinks this may happen as a side effect of some forms of tDCS. "tDCS might have much more broad effects than we think it does," he says. He points out that some neurons can mute the signals of other brain cells in their network, so it is possible that stimulating one area of the brain might reduce activity in another.

The first thing I thought of when I read this: The way drinking one (but not more than two) beers can change the way I approach a billiards game. It doesn't improve my skills, per se—I don't suddenly become graceful with a pool cue. But when it's a game that I have some skill at already, like table hockey, one beer is often just enough to allow me to stop over-thinking and just play the game ... making it feel like I'm better at it then than I am stone-cold sober. I'd be really interested to know if/how these experiences are related.

The biology of itching and the biology of pain are intertwined in interesting ways, writes graduate student and science blogger Aatish Bhatia. Understanding itching can help us better understand how to treat pain. I'd not seen Bhatia's blog before, but I'm really liking his style. He does a great job of breaking down the science in a clear way.

... In the last decade, researchers have learned about receptors in the nerves under our skin that react specifically to itchy substances. When these receptors fire, they send a signal racing up our spinal cord, headed to our brain where it creates an urge to scratch. Scientists now have a basic map of the roads that an itch takes on its way to our brain. And they have even been able to block some of these roads in mice, essentially preventing them from feeling an itch.

...The picture that is emerging is a complex one, where pain and itch signals are distinct yet subtly intertwined. Of the nerve cells under our skin, some are involved only in signalling pain, and they have pain receptors. Others are responsible for signalling different types of itches, and they have both itch and pain receptors. If the same cell has both receptors, how do we distinguish itch from ouch?

... As the biology of itching becomes better understood, the benefits are making their way from the lab to the clinic. The drug morphine is a powerful painkiller, but has a common side effect of itchiness. Women taking opiates to relieve their labour pain often experience a similar side effect. Zhou-Feng Chen and Yan-Gang Sun, authors of the GRPR receptor study, teamed up with colleagues at the newly founded Center for the Study of Itch and managed to tackle this problem. Their results, published in the current issue of the journal Cell, show that the benefits of morphine can be separated from the itch.

Via Greg Laden

Image: llama itch, a Creative Commons Attribution (2.0) image from davedehetre's photostream

I love serendipity. On the same day that Anja Austerman posted this awesome knit hat to my Google+ feed, Kevin Zelnio also posted a link reminding me of the existence of the The Museum of Scientifically Accurate Fabric Brain Art. Xeni posted about the museum here back in 2008. But it's awfully fun to contrast the super-detailed brain art on display there with this more whimsical variety.

"The Seductive Allure of Neuroscience Explanations," published in 2008 in the Journal of Cognitive Neuroscience, experimentally verifies the hypothesis that laypeople find explanations for psychological phenomena compelling because adding "neuroscience" makes them sound true:

In line with this body of research, we propose that people often find neuroscience information alluring because it interferes with their abilities to judge the quality of the psychological explanations that contain this information. The presence of neuroscience information may be seen as a strong marker of a good explanation, regardless of the actual status of that information within the explanation. That is, something about seeing neuroscience information may encourage people to believe they have received a scientific explanation when they have not. People may therefore uncritically accept any explanation containing neuroscience information, even in cases when the neuroscience information is irrelevant to the logic of the explanation.

To test this hypothesis, we examined people’s judgments of explanations that either do or do not contain neuroscience information, but that otherwise do not differ in content or logic. All three studies reported here used a 2 (explanation type: good vs. bad) × 2 (neuroscience: without vs. with) design. This allowed us to see both people’s baseline abilities to distinguish good psychological explanations from bad psychological explanations as well as any influence of neuroscience information on this ability. If logically irrelevant neuroscience information affects people’s judgments of explanations, this would suggest that people’s fascination with neuropsychological explanations may stem from an inability or unwillingness to critically consider the role that neuroscience information plays in these explanations.

(via Kottke)

(Image: DSCN0746, a Creative Commons Attribution Share-Alike (2.0) image from niels_olson's photostream)