Functional Magnetic Resonance Imaging: Round 2

June 30, 2009  |  Posted by John Medina | No Comments
This is the second installment in a 3-part series (read 1st column here) that discusses some of the mechanisms behind functional magnetic resonance imaging (fMRI) technology. As you may recall, the genesis for this series was reactive…I got mad while sitting on an airplane reading a magazine article about how fMRIs can predict everything from product preferences to political inclination. The article hinted at something I have been noticing with increasing alarm—the confusion about what fMRI can and cannot reveal about information processing in the brain. I decided to write this series hoping that knowledge of the basic science behind fMRI technology could contribute to making more nuanced conclusions about the data it reveals.

Last month, I discussed some of the basic physics behind MRI and described why magnets and radio waves were so important in getting an image. Here I explore how that physics reveals neural activity in the brain. Actually, fMRI does not detect neural activity at all. It only detects changes in blood flow, which may be a source of some of the confusion (more on that in a moment).

To talk about the controversies about what fMRI actually detects (and yes, there are controversies), I will briefly describe the relationship between neural activity and the brain’s hemodynamic properties. I will then move to data that appear to describe the molecular components behind this relationship. Along the way, I will review some basic biochemistry, from glycolysis (remember glycolysis?) to the prostaglandin biosynthetic pathway.

Read the article
You can feel your body responding to stress: Your pulse races, your blood pressure rises, and you feel a massive release of energy. That’s the famous hormone adrenaline at work. It’s spurred into action by your brain’s hypothalamus, that pea-size organ sitting almost in the middle of your head. When your sensory systems detect stress, the hypothalamus reacts by sending a signal to your adrenal glands, lying far away on the roof of your kidneys. The glands immediately dump bucketloads of adrenaline into your bloodstream. The overall effect is called the fight or flight response.

But there’s a less famous hormone at work, too—also released by the adrenals, and just as powerful as adrenalin. It’s called cortisol. You can think of it as the “elite strike force” of the human stress response. It’s the second wave of our defensive reaction to stressors, and, in small doses, it wipes out most unpleasant aspects of stress, returning us to normalcy.

Why do our bodies need to go through all this trouble? The answer is very simple. Without a flexible, immediately available, highly regulated stress response, we would die. Remember, the brain is the world’s most sophisticated survival organ. All of its many complexities are built toward a mildly erotic, singularly selfish goal: to live long enough to thrust our genes on to the next generation. Our reactions to stress serve the live-long-enough part of that goal. Stress helps us manage the threats that could keep us from procreating.

And what kinds of sex-inhibiting threats did we experience in our evolutionary toddlerhood? It’s a safe bet they didn’t involve worrying about retirement. Imagine you were a cave person roaming around the east African savannah. What kinds of concerns would occupy your waking hours? Predators would make it into your top 10 list. So would physical injury, which might very well come from those predators. In modern times, a broken leg means a trip to the doctor. In our distant past, a broken leg often meant a death sentence. The day’s climate might also be a concern, the day’s offering of food another. A lot of very immediate needs rise to the surface, needs that have nothing to do with old age.

Why immediate? Most of the survival issues we faced in our first few million years did not take hours, or even minutes, to settle. The saber-toothed tiger either ate us or we ran away from it—or a lucky few might stab it, but the whole thing was usually over in less than half a minute. Consequently, our stress responses were shaped to solve problems that lasted not for years, but for seconds. They were primarily designed to get our muscles moving us as quickly as possible, usually out of harm’s way. You can see the importance of this immediate reaction by observing people who cannot mount a thorough and sudden stress response. If you had Addison’s disease, for example, you would be unable to raise your blood pressure in response to severe stress, such as being attacked by a mountain lion. Your blood pressure would drop catastrophically, probably putting you into a state of debilitating shock. You would become limp. Then you would become lunch.

These days, our stresses are measured not in moments with mountain lions, but in hours, days, and sometimes months with hectic workplaces, screaming toddlers, and money problems. Our system isn’t built for that. And when moderate amounts of hormone build up to large amounts, or when moderate amounts of hormone hang around too long, they become quite harmful. That’s how an exquisitely tuned system can become deregulated enough to affect a dog in a metal crate—or a report card, or a performance review.

Learn more about Brain Rules.


Rule #8: Stressed brains don't learn the same way.

  • Your brain is built to deal with stress that lasts about 30 seconds. The brain is not designed for long term stress when you feel like you have no control. The saber-toothed tiger ate you or you ran away but it was all over in less than a minute. If you have a bad boss, the saber-toothed tiger can be at your door for years, and you begin to deregulate. If you are in a bad marriage, the saber-toothed tiger can be in your bed for years, and the same thing occurs. You can actually watch the brain shrink.
  • Stress damages virtually every kind of cognition that exists. It damages memory and executive function. It can hurt your motor skills. When you are stressed out over a long period of time it disrupts your immune response. You get sicker more often. It disrupts your ability to sleep. You get depressed.
  • The emotional stability of the home is the single greatest predictor of academic success. If you want your kid to get into Harvard, go home and love your spouse.
  • You have one brain. The same brain you have at home is the same brain you have at work or school. The stress you are experiencing at home will affect your performance at work, and vice versa.
View Stress and the brain tutorial

Stress at work video

Stress References (PDF)

Happy marriage can equal happy baby

May 4, 2009  |  Posted by John Medina | No Comments
People love to give advice to expectant couples. Some of it is trite ("Cherish every moment"); some is useful ("Go to as many movies as you can before the baby comes").

But no one warns couples about what can happen to a marriage after the baby arrives.

Read "Happy marriage can equal happy baby" in the St. Louis Post-Dispatch.


From where do the statistics on the transition to parenthood come? The comments in this article probably need to have some nuance added to them in order to make the most sense. These additional comments are enumerated below, including the references for all figures cited here and in the above sections.

It is clear that marital satisfaction declines for both members of the couple, sometimes catastrophically, during the transition to parenthood. The female in the relationship generally achieves the 70% figure first (though in some studies the actual figure is between 40 -70%). The male satisfaction scores starts declining afterward, perhaps as a reaction to female behavior. Here are two relevant references:

Gottman, JM (1999)
The Marriage Clinic: a Scientifically-Based Marital Therapy
Norton Prof Books (NY)
pp. 119 – 133 (see in particular p. 120 – 121)

Belsky, J and Pensky E (1988)
Marital change across the transition to parenthood
Marr and Fam Rev 12: 133 – 156

The nine-fold figure at the half-year mark is actually from unpublished data. The true number has been elusive to determine, even after all these years, probably because different studies use different hostility indices to arrive at their conclusions. Regardless of the methodology employed, the conclusion is very straightforward, and sobering: it is not abnormal to experience a great increase in conflict during the transition to parenthood (for some couples, it is probably much higher than 9x). Here are references filled with the most solidly designed studies:

Wallace, PM & Gotlib IH (1990)
Marital adjustment during the transition to parenthood: stability and predictors of change
J. Mar & Fam 52(1): 21 – 29

Belsky, J and Kelly J. (1994)
The transition to parenthood: How a first child changes a marriage and why some couples grow closer and others apart
Dell (NY)

Learn more about Brain Rules.

This is Your Brain at Work

April 28, 2009  |  Posted by John Medina | No Comments
John Medina was recently interviewed by the New York Post. The complete article, "This is Your Brain at Work," is available here.

How is work an antibrain environment?

We don't very much know how the brain works, but we do know something about its performance envelope. The brain appears to have been designed to solve problems related to surviving in an outdoor setting in unstable meteorological conditions. And to do that in near-constant motion. That's what the brain's good at. So if you wanted to design a work environment directly opposed to what the brain was naturally good at doing, you'd design something like an office.

If you tore the workplace down, what would you replace it with?

We've known for some time that the more fit aerobically you are, the better a particular series of processes called "executive function" in the brain works. It helps your ability to do math. It helps your ability to control your impulses. It helps with Let's say you're a Boeing engineer. Executive function is the very thing that allows you to design a satellite and, at the same time, keeps you from punching your boss in the nose when you get a bad performance review.

If you take somebody who's fat and sedentary and exercise them three times a week for as little as three months, you can get anywhere between an 80 and 120 percent increase in executive function. In our evolutionary history, we were probably walking anywhere between 10 and 20 kilometers per day. If we sat around in the Serengeti for half an hour, we were usually lunch.

Scotch the cubicle, put in a treadmill and do all your computer work while you're walking two miles an hour.

How does sleep, or lack of it, affect the brain at work?

There's a time in the afternoon when your brain wants to do a reset. And during that time it wants to take a 15- to 20-minute nap. We call it the nap zone. If you don't allow yourself to take a nap during that time, you'll fight being sleepy the rest of the afternoon, and productivity can suffer.

It was measured by NASA. They were able to show that by giving their fighter pilots a 20-minute nap in the nap zone, you'd find an increase of about 34 percent in their mean reaction time performances.

Mark Rosekind, the guy who did the study, goes, "Look, what other management technique can I do that, in 20 minutes, gives a 34 percent boost in productivity?"

Related Links:

Interview in the New York Post

Sleep Slide Show

Why do we sleep?

Exercise boosts brain power

Discuss on the Facebook fan page

Brain Rules for public speaking

April 22, 2009  |  Posted by John Medina | No Comments
Scott Berkun recently interviewed John Medina for his blog Speaker Confessions. Scott asks the question: what makes public speakers good or bad? He's working on a book to answer that question.

SB: How can a lecturer use attention, but make sure not to abuse it? Or put another way, does repetitive use of phasic alertness, getting an audience to refocus their attention ever few minutes, have declining effects over time?

JM: I do not believe in entertainment in teaching, during the holy time information is being transferred from one person to another. I do believe in engagement, however, and there is one crucial distinction that separates the two: the content of the emotionally competent stimulus (“hook”). If the story/anecdote/case-history is directly relevant to the topic at hand (either illustrating a previously explained point or introducing a new one), the student remains engaged. Cracking a joke for the sake of a break, or telling an irrelevant anecdote at a strategic time is a form of patronizing, and students everywhere can detect it, usually with resentment, inattention or both.

Do you think the size of a classroom has any effect on students ability to pay attention? Does Posner’s model of attention change if we are alone in conversation, vs. in an audience of 99 other people listening to a lecture?

I don’t think the size of the classroom has anything to do with the functional neural architecture proposed by Posner, but there is a universe of difference in how it behaves. The behavior has to do with our confounded predilection for socializing. People behave very differently in large crowds than they do in small crowds or even one on one. Very different teaching strategies must be deployed for each.

Bligh’s book “What’s the use of Lectures?” identifies 18-25 minutes, based on his assesment of psychology studies, as the key breakpoint for human attention in classrooms. Whether it’s 10 or 25, why do you think so few schools or training events use these sized units as the structure for their days, or their lessons?

I don’t know why schools don’t pay attention to attention. Perhaps it is a lack of content knowledge. If I had my way, every teacher on the planet would take two courses: First, an acting course, the only star in the academic firmament capable of teaching people how to manipulate their bodies and voices i to project information. Second, a cognitive neuroscience course, one that teaches people how the brain learns, so teachers can understand that such projections follow specific rules of engagement.