Researchers prove that precisely timed brain stimulation improves memory

February 6, 2018, University of Pennsylvania
Credit: Wikimedia Commons

Precisely timed electrical stimulation to the left side of the brain can reliably and significantly enhance learning and memory performance by as much as 15 percent, according to a study by a team of University of Pennsylvania neuroscientists published in Nature Communications. It is the first time such a connection has been made and is a major advance toward the goal of Restoring Active Memory, a U.S. Department of Defense-sponsored project aimed at developing next-generation technologies to improve memory function in veterans with memory loss.

"Our study has two novel aspects," said Youssef Ezzyat, a senior data scientist in Penn's psychology department in the School of Arts and Sciences and lead author on the paper. "We developed a system to monitor brain activity and trigger stimulation responsively based on the subject's brain activity. We also identified a novel target for applying stimulation, the left lateral temporal cortex."

In previous work by the Penn team, led by Michael Kahana, professor of psychology and RAM program principal investigator, and Daniel Rizzuto, director of cognitive neuromodulation, electrical pulses were delivered at regular intervals, independent of a subject's success at learning. For example, during a free-recall memory task, researchers presented words on a screen for the patient to learn, and they applied with every other word in an effort to improve the outcome. In this case, the stimulation was not in response to specific brain-activity patterns.

In the current study, they took a different tack, one that included monitoring a patient's brain activity in real time during a task. As the patient watched and attempted to absorb a list of words, a computer tracking and recording brain signals would make predictions based on those signals and then prompt an electrical pulse, at safe levels and unfelt by the participants, when they were least likely to remember the new information.

"During each new word the patient viewed, the system would record and analyze brain activity to predict whether the patient had learned it effectively. When the system detected ineffective learning, that triggered stimulation, closing the loop," Ezzyat said.

After stimulation was turned off, the system would again listen to the subject's brain activity, waiting for the next appropriate opportunity to generate the pulse.

The study involved 25 neurosurgical receiving treatment for epilepsy. Patients participated at clinical sites across the country, including the Hospital of the University of Pennsylvania, Thomas Jefferson University Hospital, University of Texas Southwestern, Emory University Hospital, Dartmouth-Hitchcock Medical Center and Mayo Clinic. All subjects had already had electrodes implanted in their brains as part of routine clinical treatment for epilepsy.

To build the models that used brain activity to make predictions, each participant performed the free-recall memory task during at least three 45-minute sessions before the Penn team introduced any closed-loop stimulation; multiple sessions increased the confidence that the linked to ineffective learning reflected a true pattern rather than an accidental blip. Patients then took part in at least one session involving brain stimulation.

"By developing patient-specific, personalized, machine-learning models," Kahana said, "we could program our stimulator to deliver pulses only when memory was predicted to fail, giving this technology the best chance of restoring . This was important because we knew from earlier work that stimulating the brain during periods of good function was likely to make memory worse."

With this finding, the four-year RAM project comes closer to a fully implantable neural monitoring and stimulation system. The researchers said they believe there is great potential for the therapeutic benefits of this stimulation, particularly for people with and Alzheimer's disease.

"Now we know more precisely," Rizzuto said, "where to stimulate the brain to enhance memory in patients with disorders, as well as when to stimulate to maximize the effect."

Michael Sperling, clinical study investigator at Thomas Jefferson University Hospital, added, "We are now able to monitor when the seems to be going off course and to use stimulation to correct the trajectory. This finding took an incredible amount of effort by not only the researchers but also by our patients, who were extraordinarily dedicated to participating in this project so that others might be helped."

Explore further: Researchers show brain stimulation restores memory during lapses

More information: Youssef Ezzyat et al. Closed-loop stimulation of temporal cortex rescues functional networks and improves memory, Nature Communications (2018). DOI: 10.1038/s41467-017-02753-0

Related Stories

Researchers show brain stimulation restores memory during lapses

April 20, 2017
A team of neuroscientists at the University of Pennsylvania has shown for the first time that electrical stimulation delivered when memory is predicted to fail can improve memory function in the human brain. That same stimulation ...

Tickling the brain with electrical stimulation improves memory, study shows

January 29, 2018
Tickling the brain with low-intensity electrical stimulation in a specific area can improve verbal short-term memory. Mayo Clinic researchers report their findings in Brain.

Team constructs whole-brain map of electrical connections key to forming memories

November 22, 2017
A team of neuroscientists at the University of Pennsylvania has constructed the first whole-brain map of electrical connectivity in the brain based on data from nearly 300 neurosurgical patients with electrodes implanted ...

Neuroscientists improve human memory by electrically stimulating brain

October 25, 2017
Neuroscientists at the David Geffen School of Medicine at UCLA have discovered precisely where and how to electrically stimulate the human brain to enhance people's recollection of distinct memories. People with epilepsy ...

Brain implant tested in human patients found to improve memory recall

November 15, 2017
(Medical Xpress)—A team of researchers with the University of Southern California and the Wake Forest School of Medicine has conducted experiments involving implanting electrodes into the brains of human volunteers to see ...

Direct amygdala stimulation can enhance human memory

December 18, 2017
Direct electrical stimulation of the human amygdala, a region of the brain known to regulate memory and emotional behaviors, can enhance next-day recognition of images when applied immediately after the images are viewed, ...

Recommended for you

Animal study connects fear behavior, rhythmic breathing, brain smell center

April 20, 2018
"Take a deep breath" is the mantra of every anxiety-reducing advice list ever written. And for good reason. There's increasing physiological evidence connecting breathing patterns with the brain regions that control mood ...

Mechanism behind neuron death in motor neurone disease and frontotemporal dementia discovered

April 20, 2018
Scientists have identified the molecular mechanism that leads to the death of neurons in amyotrophic lateral sclerosis (also known as ALS or motor neurone disease) and a common form of frontotemporal dementia.

When there's an audience, people's performance improves

April 20, 2018
Often, people think performing in front of others will make them mess up, but a new study led by a Johns Hopkins University neuroscientist found the opposite: being watched makes people do better.

Signaling between neuron types found to instigate morphological changes during early neocortex development

April 20, 2018
A team of researchers from several institutions in Japan has found that developing neocortex neurons in mammals undergo a morphological transition from a multipolar shape to a bipolar shape due at least partially to signaling ...

MRI technique detects spinal cord changes in MS patients

April 20, 2018
A Vanderbilt University Medical Center-led research team has shown that magnetic resonance imaging (MRI) can detect changes in resting-state spinal cord function in patients with multiple sclerosis (MS).

Gene variant increases empathy-driven fear in mice

April 20, 2018
Researchers at the Center for Cognition and Sociality, within the Institute for Basic Science (IBS), have just published as study in Neuron reporting a genetic variant that controls and increases empathy-driven fear in mice. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.