For 20 years now, scientists have been spying on the brain. The technique they use, called functional MRI, has changed the face of brain science, illuminating aspects of the human mind at work without the need for brain surgery or radioactive tracers.
Just lie in a noisy metal tube for a while, and then presto — out pops a gorgeous image of a live brain. (OK, not really. Before that presto comes lots of complicated work, like preprocessing the data, choosing the right comparison, figuring out exactly where to look, fancy statistical tests and more. And of course, scientists still don’t agree on what exactly the pretty pictures represent. But still.)
fMRI’s influence on neuroscience is clear from the variety of findings the technique has provided. Scientists have used it to identify brain regions involved with bluffing in a card game, having feet tickled mercilessly and, as a paper in the August Journal of Urology describes, urinating. (I hope that those volunteers were compensated to the fullest extent.) People have been terrified by live snakes while lying in an fMRI scanner, teased with contagious yawns and tempted with cupcakes. And the scanner experience is no longer restricted to a solo adventure: A new duet fMRI design captures brain activity of a couple squeezed in tight and gazing into each other’s eyes.
In addition to revealing things about the brain, fMRI’s meteoric rise from the first publications about it in the early ’90s to its use today by thousands of researchers also reveals things about how to do good science. Out of fMRI’s origin story comes an adage: Always pay attention to weirdness.
That doesn’t mean you have to talk to that guy who Rollerblades down your block wearing a leopard print. But it means that sometimes the most outstanding discoveries are in danger of being overlooked because they don’t fit in.
One of the most important discoveries enabled by fMRI almost didn’t happen, because this discovery wasn’t tied to any task at all. Forget the gambling tasks, sniff tests and memory quizzes. Such busywork obscures something the brain naturally does when left to its own devices. As the brain starts do to absolutely nothing, an intricate series of interconnected brain hubs, like stations in the subway system, kick into gear.
Early on, these mysterious signals that accompanied the resting brain were largely disregarded, writes Randy Buckner of Harvard University, an fMRI pioneer. “Part of the reason was that we didn’t understand them,” he recounts in the Aug. 15 NeuroImage, which is devoted to fMRI’s 20th birthday. “They fell victim to the always-present bias to ignore what is least understood.”
Most brain researchers looked for ways to get rid of these signals, mathematically canceling them into oblivion because they interfered with the “real” results of what the brain is doing during a particular task. But the problem didn’t go away. Buckner and others found themselves confronted with brains that refused to sit quietly and behave. As more and more data suggested that the brain really was up to something when appearing to be up to nothing, some scientists finally faced this menace. In 2001, this phenomenon ceased to be an annoying artifact and was recognized with a name: the “default mode network.”
Since then, the default mode network has been implicated in a wide variety of brain business. Some scientists think this constellation of brain systems is required for quiet, introspective thinking. Remembering your favorite pet, mulling over social interactions and thinking about the future may fall under the default mode network’s purview.
Default mode network malfunctions may be linked to neurological disorders such as Alzheimer’s, autism and schizophrenia. Some researchers, including Buckner, think that there may be even bigger things in store for the default mode network. Far from being content to laze about, the default mode network may actively assist people in certain situations, Buckner writes.
It’s too soon to say for sure just how important the default mode network is, but this once-ignored system could be a big clue to some of the most fundamental mysteries of how the brain works.
Ignoring the mysterious isn’t new to science. One of the biggest discoveries in genetics — the stretches of DNA that don’t hold genes — was dismissed as “junk DNA” in the early days of gene sequencing. Later, scientists found out that the so-called junk is actually brimming with treasure, directing the behavior of a wild collection of important molecules that scientists had successfully ignored.
Which is to say, we are lucky to have scientists who were not content to ignore those inexplicable brain signals. Because sometimes, the most momentous discovery starts with a “Hey, that’s weird.”