Interviewees: Sarah Lisanby, Columbia University
Stimulation for Sleepiness
Short on sleep? Besides the bags under your eyes, you may have difficulty remembering names, phone numbers, and other stuff you store in short-term memory. Brain researchers at Columbia University and the New York State Psychiatric Institute can’t do much for tired-looking faces, but they’re now exploring a method for refreshing your sleep-deprived brain.
By using magnetic fields to stimulate certain brain regions of sleep-deprived volunteers, Sarah Lisanby and her team found that they could improve people’s performance on a short-term memory test. “We looked to see whether that would help these people become more resilient to sleep deprivation. And our study, our results, suggested just that,” Lisanby says.
The technique, called Transcranial Magnetic Stimulation or TMS, gives a magnetic wake-up call to specific regions of the brain. TMS delivered to sleepy subjects improved their speed as they tried to recall what letters had flashed on a computer monitor seven seconds earlier.
TMS is still experimental, but it’s also shown promise in the treatment of depression and is being tested for other conditions including anxiety disorders and schizophrenia.
And because sleep deprivation can serve as a model for other types of memory problems, the research may lead to treatments for age-related memory loss, for instance. Lisanby says, “By studying sleep deprivation with these new tools, we were hopeful to establish a paradigm that could be applied in other situations where memory is affected, such as dementia.”
In their study, the researchers used TMS as a research tool to study how sleep deprivation affected working memory function and the brain. So they needed to make sure volunteers were plenty tired.
Volunteers were monitored in a lab for 57 hours straight, no coffee or nodding off allowed. Then, to figure out what brain regions to target, the researchers took MRI scans of the brains of sleep-deprived and normal subjects.
They found that sleep deprivation did not affect every volunteer’s short-term memory the same way. “You may have personal experience with this, that different individuals vary in the degree to which they’re affected by sleep deprivation,” explains Lisanby. “An aspect of this experiment was to try and understand what’s different in the brains of people who are resilient to sleep deprivation compared to those who are more affected by it.”
By analyzing results of the memory test, the researchers picked out a group of volunteers who stayed sharp, even after two all-nighters. The next step was to examine these people’s MRI scans to figure out which brain networks were responsible for the memory boost.
“We could see what brain networks were more activated in those people who were more resilient to the sleep deprivation,” says Lisanby.
But she says, “Just seeing that that network is more active in the resilient person doesn’t prove that that’s how they were doing it, that that’s how they were resisting the sleep deprivation.” That’s why they used TMS, “guided by those brain imaging results, to test whether that network was responsible for those people’s ability to be resilient to sleep deprivation,” Lisanby explains.
Simply put, the researchers saw what worked for the resilient volunteers, and they used TMS to replicate that beneficial brain state in the volunteers most affected by losing sleep.
While the MRI scans provide the maps of each volunteer’s brain, they can’t steer the magnetic fields. So to make sure the magnets hit the right spot, the researchers hook up the TMS device to an infrared camera that tracks the research subject’s location in the lab room. The camera and the MRI data both feed to a computer, and the computer tells the researcher where to aim the magnet. Lisanby’s co-author, Bruce Luber, says TMS is accurate enough to send the magnetic signal to within millimeters of the targeted brain region.
As the researchers wrote in the journal Cerebral Cortex, TMS recipients were speedier in memory tests following the treatment.
Lisanby says, “That’s the part that we find really exciting, that not only has it taught something new about how the brain works, how the brain responds when you’re sleep-deprived, but it also might shed light on a new direction for using image-guided TMS as a way of improving memory in the future.”
The research, which was funded by the Department of Defense, may one day be able to help sleep-deprived soldiers, says Lisanby. “Our men and women in uniform might be in missions where they need to be sleep-deprived for certain periods of time. So that’s another situation where it’s important to learn about how sleep deprivation affects our function,” she says.
Could TMS also be used to improve performance if you aren’t short on sleep? In their 2007 paper published in the journal Brain Research, the researchers showed that they could improve working memory slightly in well-rested people as well. But for TMS to make a difference for these normal volunteers, it needed to target different brain regions than those targeted in the sleep-deprived group.
“The region of the brain that helped the people who weren’t sleep-deprived was actually different from the brain region that helped the people who were sleep-deprived,” Lisanby explains.
But that doesn’t mean you’ll be boosting your brain with TMS tomorrow. “We’re at the very early stages of this research,” she says. “It’s a far leap before we would get to the point where something like this would be of use outside of the laboratory. But it’s certainly something that we hope that research will begin to look towards.”
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