The Physics of fMRI

April 13, 2009  |  Posted by John Medina | No Comments
I almost destroyed the backseat pocket of an airline seat this summer. The vandalism was inadvertent, assuredly, though the anger that fueled it was not. While waiting for my plane to take off, I had read a magazine article claiming to show that fMRI (functional magnetic resonance imaging) studies were “uncovering” the voting preferences of test subjects. An adjacent article announced that researchers could now predict the buying preferences of other test subjects using the same imaging technologies.

I was puzzled. How could Fourier transforms performed on signals coming from someone’s cortex say anything about their politics? What could possibly have reduced the interpretation of these noninvasive imaging data to conceptual phrenology? I got so mad as I thought more about it that I jammed the articles back into the pocket, aggravating an already ripped inner seam.

The column you are reading is an attempt to push this admittedly hot reaction into a more positive direction. . . and for a good reason. There are growing numbers of articles in the popular press describing “breakthroughs” in our understanding of human cognition—and how noninvasive imaging data are changing the way we view the brain. Nothing wrong with that, certainly. There has been an explosion of studies using functional (f)MRI technologies and their like. But are the data being revealed strong enough to predict subjective behaviors, such as voting habits? As you can probably guess from my tone, the answer of this bioengineer is “no,” or at least “not yet.”

I have decided to do something positive about these “headlines.” For now, and in my next 2 columns, I will describe how fMRIs actually work and what is the least luxurious, most conservative way to interpret the view they give us about cognition. Given the conceptual and technical complexity, it is easy to misconstrue what imaging technologies can divulge about human cognition.

Starting with quarks (literally) and ending with scans of emotional behavior, we will explore some of the biophysical underpinnings of this promising (and may I say limited) technology. The hope is that by knowing a bit about the technical aspects of fMRI, we will better understand what it can—and cannot—measure. This will allow us to treat with greater skepticism, and more sobered excitement, the view that fMRIs are giving us about how our brains work.

This first installment deals with some basic physics. I review a few properties about magnets and radio waves that you might not have thought about since your undergraduate days. In part 2, I will focus on the types of molecular interactions these magnets and radio waves actually measure when trained on an actively thinking brain. The third column will relate how this knowledge reveals both the strengths and limitations of using imaging technologies to discover aspects of human cognition.

We begin with the name. As you know, fMRI is short for functional magnetic resonance imaging. The core idea of fMRI has been around for a long time. Originally called just NMR (nuclear magnetic resonance), this technology found great utility in the organic and inorganic laboratories. When it came time to apply the technology to biological tissues (from ideas originally developed by Paul Lauterbur), the word “nuclear” was thought to have too many negative connotations. It was dropped in favor of the more socially compatible “functional.”

To understand how an fMRI scanner generates images, we have to break the machine down into its component parts. All fMRIs possess 3 general “gadgets.” The first is a device that can generate a powerful magnetic field. The second is a coil that can create powerful radio frequency pulses. The third is a highspeed computer, preloaded with a lot of very sophisticated signal processing software, all programmed to produce an image capable of making sense to a researcher. How these 3 gadgets work together is fairly easy to understand, at least at the 40,000-foot level. The magnet in the fMRI transforms tissues into a visualizable state; the radio frequency pulses provide the signaling information necessary to discern them. The computer assembles the information from the radio frequency pulses into a form instantly recognizable to anyone who can read a weather map. Indeed, part of the problem with misinterpreting fMRIs is that the information seems so accessible.

To make sense of how these gadgets work together, we have to understand how magnets and radio frequencies act at the subatomic level. These interactions are essentially the same physical
processes you see on display every time you turn on your radio.

Download the PDF to read the rest

This column appeared in the April issue of Psychiatric Times. More columns available here.

Paperback Available Now and Summer Workshops

March 31, 2009  |  Posted by John Medina | No Comments
The following was emailed to our Brain Rules Newsletter subscribers. If you want to receive email updates about 2x a year, sign up to subscribe to the newsletter.

Brain Rules Paperback Now in Stores
We are happy to report that the Brain Rules paperback is now available. The paperback includes a special link to watch the DVD online. You can pick up a copy at any bookstore. Links to buy online are here.

Brain Rules Workshops
Spend a day with John Medina as he takes the research and ideas in Brain Rules to the next level. Seattle Pacific University is hosting Brain Rules for Education (for teachers, principals, superintendents, and administrators).

Brain Rules for Education- Seattle
Thursday, June 25, 2009
Thursday, July 16, 2009
8:30 am - 4:30 pm
Register and learn more:

Register now to secure your spot as seating will be limited.

Cool Links to Share

There's a ton happening online related to the book. Here are some links to check out:

Sleep Well, Think Well - learn why we spend 1/3 of our lives sleeping
Brain Rules for Presenters - Garr Reynolds shows how Brain Rules relates to presentations
YouTube - more than 30 Brain Rules videos
Authors@Google talk - watch John Medina's 50-minute talk at Google
Tutorials - explore each brain rule through charts, audio, and video
Twitter - follow the action on Twitter
Mind Map - interactive outline of all 12 Brain Rules
Facebook - become a fan of John's, watch videos, discuss the book, and more

Brain Rules T-Shirts
We now have our own t-shirts. If you'd like a free t-shirt, order 7 copies of either the paperback or hardcover from an online bookseller by April 15, 2009 (tax day). Simply forward your email receipt to with the subject "t-shirt." Let us know your size and mailing address. Offer is only good for U.S. addresses.

Thanks for sharing this with your friends and colleagues. Remember, curiosity is everything.

Mark Pearson
Pear Press

P.S. If you received this email from a friend, sign up to subscribe to the newsletter.

The 10 Minute Rule

March 18, 2009  |  Posted by John Medina | No Comments
So I ask this question in every college course I teach: “Given a class of medium interest, not too boring and not too exciting, when do you start glancing at the clock, wondering when the class will be over?” There is always some nervous shuffling, a few smiles, then a lot of silence. Eventually someone blurts out:

“Ten minutes, Dr. Medina.”

“Why 10 minutes?” I inquire.

“That’s when I start to lose attention. That’s when I begin to wonder when this torment will be over.” The comments are always said in frustration. A college lecture is still about 50 minutes long.

Peer-reviewed studies confirm my informal inquiry: Before the first quarter-hour is over in a typical presentation, people usually have checked out. If keeping someone’s interest in a lecture were a business, it would have an 80 percent failure rate. What happens at the 10-minute mark to cause such trouble? Nobody knows. The brain seems to be making choices according to some stubborn timing pattern, undoubtedly influenced by both culture and gene. This fact suggests a teaching and business imperative: Find a way to arouse and then hold somebody’s attention for a specific period of time.

"10 Minute Rule" slide with audio

To learn more about how Brain Rules relates to presentations, check out Garr Reynolds's Brain Rules for Presenters slideshow. Garr is the author of Presentation Zen.

Fishing for Genetic Links in Autism

March 4, 2009  |  Posted by John Medina | No Comments
This is the second installment in a 2-part series that addresses approaches to understanding the molecular underpinnings of autism. Learn more about "Brain Rules" here.

In my January column (“Fishing Expeditions and Autism: A Big Catch for Genetic Research?” Psychiatric Times, January 2009), I described the great difficulties researchers face characterizing the genetic basis of the disease. Complexities range from trying to establish a stable diagnostic profile to making sense of the few isolated mutations that show clear associations (either with disease or syndrome variants).

Using the metaphor of a fishing net, I discussed 2 overall research strategies that geneticists commonly use to catch these elusive sequences of interest. One strategy is to cast nets that act like large purse seiners to collect many sequences in a single (and usually quite expensive) effort. The other strategy is akin to dropping a single fishing line into the genetic waters to see if anything “bites.” In Part 1, I described one particularly successful strategy that snagged a large number of useful sequences.

Here, the focus narrows: I will not describe the isolation of many sequences, but rather only one. Our “catch” is called MeCP2, a gene whose mutations can give rise to a wide spectrum of related postnatal neurodevelopmental disorders—including autism spectrum disorders. I will start with some background regions about gene regulation, move to the biological functions of MeCP2, and then focus on studies in animal models that provide tantalizing hints about the origins of autistic behavior. My goal is to show that research progress in autism is a continuum of efforts, ranging from large projects with lots of identifiable sequences to small projects that focus on the properties of single genes.

Download the PDF of the complete article

- Theory of Mind
This article first appeared in the Psychiatric Times. Learn about Brain Rules here.

I am a fan of the television show Deadliest Catch—a documentary series that follows the travails of deep-sea fishermen in the Bering Sea. (Actually, it is mostly about deep crab fishing.) Living in Seattle, I have actually seen some of the boats filmed on the show.

The variety of equipment the fishermen use to capture sea life is extraordinary. Trawlers and purse seiners—boats that use long-line nets and gill nets—make it possible to catch thousands of fish at a time. I am constantly struck by the comparison between these large, industrial efforts and the “weekend” fishermen that Seattle also has by the thousands. The amateurs use simple fishing poles to catch one fish at a time. Where the Deadliest Catch boats are based, you can often see both styles side by side.

I mention these 2 contrasting styles of fish harvesting because there is a comparison that I would like to make in this month’s column and in the next. It is not much of a stretch to say that isolating the genes responsible for complex behavioral disorders can seem like fishing expeditions (complete with analogous net comparisons). There are giant efforts that deploy the molecular equivalent of purse seiners designed to snag large groups of genes that share a potential involvement in whichever presenting behavior is under study. These efforts can be contrasted with technologies that use the equivalent of small fishing poles, the goal of which is not to catch large, glittering groups of nucleotides but single genes, one at a time.

In this column and the next, we will tackle one of the most slippery issues in the behavioral sciences: the genetic basis of autism.

Download the PDF of the complete article