Erin White, Northwestern University

like the future: TMS, or transcranial magnetic stimulation, is a method of directing magnetic currents through the skull and onto the surface of the brain to physically change the way the neurons talk to one another… without all the mess of brain surgery.

Today, in a study published in the journal Science, a team of brain researchers at Northwestern University have announced that they've successfully used TMS to improve memory in healthy adults. The researchers also report that they've discovered how to use the TMS to lock into broad networks of neurons—getting at deep and otherwise out-of-reach regions of the brain by zapping connected neurons on the surface.

"I was astonished at the results" says Joel Voss, the neuroscientist leading the team, "The brain is a biological system of networks so complex that we can't even begin to comprehend them, yet with this method we're using, we were able to tease out some connections and improve memory in the process."

The Test

Voss and his colleagues took 16 healthy participants and fMRI brain imaging to find a spot on the outside of each of their brains that closely synched up with their hippocampus—an inner brain region thought to be influential in people's ability to remember associations, like names to faces.

"The fMRI measures blood flow, which is a pretty darn good marker of when neurons are active," Voss said, "we just made the very basic assumption that if the blood flow in two areas were correlated, then there was some level of connectivity."

Having locked onto each participant's outer-layer sweet spot, the scientists then subjected those spots to daily 20-minute sessions of focused TMS for five days. Halfway through the week, and then again 24 hours after the last brain zapping, the scientists took another set of fMRI images to see what had changed. They also tested the participants with a battery of different cognitive tests before, midway, and after the experiment—including a test that gauged their ability to remember the random pairing of words and faces on flashcards.

To find out whether any changes might be due to a placebo effect, the scientists also divided up the participants into two group. One week, one group received a fake treatment and one got a real TMS treatment. Two weeks later, the roles were reversed.

Better—But Not Superhuman

By the end of the week, on average, the TMS treatments improved their participants' associated memory by about 30 percent. "So if they got 10 [flashcards] right before the experiment, they got 13 after," Voss says. All other cognitive tests showed no change at all—as the experimenters expected.

"It's not like we turned [our participants] into memory champions, he says, "but this is the first time anyone has shown that it's possible to change the operation of the brain's memory network from the outside."

And by comparing the fMRIs of each participant taken before, during, and after the study, the scientists showed that the effects of the TMS zapping on the outer layer of the brain did indeed travel through the assumed neural connection and into the hippocampus.

"This really is a fantastic concept," says Michael Fox, a neuroscientist at the Harvard Medical School who was not involved in the study. "They can't stimulate the hippocampus directly, but they found another way to get there. I think that this technique—of picking targets based on their connectivity to other regions—will only become more and more important."

However, Fox did mention one potential flaw in the study: the fake test used to rule out the placebo. "The real [TMS] causes a contraction on the scalp muscles, almost like somebody is tapping on your head," he says. "The sham [TMS] feels much, much weaker. After having both, I'm fairly sure you could tell which one you had." Unfortunately, as Fox points out, the scientists did not ask their participants which procedure they thought they had, which leaves a bit more room for a placebo effect to account for some of their results.

How Does It Work?

One of the strangest things about the TMS procedure is that nobody is entirely sure what it does. Lynn Rogers a neuroscientist with the Northwestern University team, says one idea is that at the molecular level, TMS hacks and lowers the threshold that some neurons require to sense certain types of signals. And this lowered inhibition could be spread through neural connections. "If you think of your brain like a really bad driver, which is constantly using the gas and break at the same time, the TMS procedure may be convincing parts to take off some of that brake pedal," Rogers says.

While this is early-stage research, Voss and Rogers are excited about the possible application of their TMS findings and techniques to investigate ways to help people with degraded memory capabilities—such as those who suffer from Alzheimer's.

As for improving memory for an average adult, Voss believes this is unlikely because of how slight the improvement is, and the fact that the researchers believe the effect fades. While the team is still studying how long these effects last, "the magnitude of the effect we found is probably less than you'd experience from a night of drinking," Voss says. Impressive, but nothing that will help you memorize names and faces at cocktail parties.

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