Painless Zap to the Brain Resurfaces 'Forgotten' Memories

Where do memories go when we forget? They might just be hiding.

Published on 12/1/2016 at 2:00 PM

Nathan Rose lost a few days of his life. Once, when he was 10 years old doing tricks on his BMX bike without a helmet, he crashed and got a concussion. In grad school, a car slammed into him while he rode his bike for triathlon training, helmet on, and sent him flying into the road. Then the vehicle sped away. Both times he fully regained consciousness, but has no memories from those spotty stretches.

Now an assistant professor at the University of Notre Dame focused on cognitive neuroscience, Rose is determined to understand how the human brain supports memory processes. There's no filling the concussive gaps in his own memory, but his work could prevent others from losing theirs.

Today in the journal Science, he and his colleagues report on surprising results from their study using transcranial magnetic stimulation or TMS to bring back memories in healthy, alert human participants. The goal for their research was no less than understanding the neural and cognitive processes that support our ability to retain information. What they discovered goes against the long-standing view that working memory always relies on sustained activity - a use-it-or-lose-it school of thought.

Zapping the brain helped awaken short-term memories that, from a scientific standpoint, seemed lost. "The information is still there," Rose told me. "It's not forgotten, it's still in working memory, but it's being represented in a different way than the current historical theory would suggest."

For the study, which Rose worked on with University of Wisconsin–Madison psychology professor Brad Postle, each participant donned an intimidating looking but non-invasive electrode cap to record brain activity.

The researchers used a separate device to deliver transcranial magnetic stimulation or TMS. A coil inside produces a strong electrical charge that in turn generates a powerful magnetic field, which passes through the scalp, scull and membrane that wraps around the brain. TMS instantaneously activates neurons in a specific, targeted section of the brain. A quick, painless zap.

While hooked up to the equipment, each participant sat in front of a computer screen that displayed pairs of items such as a computer-generated face, a word or a path of dots moving in a certain direction. Then they were given memory tasks based on those items. Each piece of information was carefully chosen because it actually activates unique patterns of brain activity, Rose explained.

As the participants went through multi-hour sessions of memory tasks, Rose and his colleagues recorded the brain activity and fed it to machine learning algorithms that had been trained to decode the patterns. "This provides a window into 'seeing' what people are thinking of over the course of this trial, and when they are thinking about it," Rose said.

During sessions for the trial, participants had to retain two items of information simultaneously for a few seconds. One task involved remembering a face and the word "asinine." In the test to see whether the person remembered that word, Rose incorporated the rhyming prompt "frankenstein" - a sly shout-out to Jerrod Lewis-Peacock, a neuroscientist who did pioneering work on an early experiment with Postle and is now an assistant professor at UT-Austin. "When I first showed him the results, he dubbed this the 'Frankenstein effect,'" Rose said.

Rose compared the quick memory challenges in the study to ones in the real world, like when you go to a cocktail party, meet a new couple, and try to remember both of their names after you start conversing with only one of them. In the study, brain activity for an "unattended item" that the person wasn't concentrating on, dipped down to a baseline level, as if it had been forgotten. After applying a targeted pulse of TMS, the team measured brain activity that indicated the dormant memory had briefly reemerged. Whoa.

Rose finds the potential to activate the brain like this exciting for eventually addressing a wide variety of clinical conditions, including Alzheimer's and dementia. Two of his own grandparents experienced cognitive decline before they died.

Still, Rose cautioned that the cognitive process is quite dynamic. "It's not like we're bringing this memory back and people are all of a sudden being able to see the face or hear the word," he insisted. He also pointed out that they didn't see the same reactivation effect in the second half of the trial, when participants got cues saying they no longer needed to retain the info. "This research has really opened up more questions than it's answered," he added.

Even though the current tech can't recover Rose's long-lost memories, he hopes that a combination of behavioral and neurophysiological interventions will support better memory functioning in the long run. "If there are ways to sort of enhance the consolidation of memories through these non-invasive brain stimulation techniques, that would be pretty incredible, right?" That's the dream, and this guy took a step toward it.

"We have shown some evidence for a targeted reactivation of a specific memory that is being representative in working memory - in sort of an activity silent manner," Rose said. So the name of that person who walked over to the punch bowl might seem elusive, but it's probably not gone. Just hiding.

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