Deep-brain stimulation during sleep strengthens memory
Researchers also report first direct evidence supporting main theory for
how human memory is consolidated during sleep

Date:
June 1, 2023
Source:
University of California - Los Angeles Health Sciences
Summary:
New research provides the first physiological evidence from inside
the human brain supporting the dominant scientific theory on how
the brain consolidates memory during sleep. Further, deep-brain
stimulation during a critical time in the sleep cycle appeared to
improve memory consolidation.


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FULL STORY ========================================================================== While it's known that sleep plays a crucial role in strengthening memory, scientists are still trying to decode how this process plays out in the
brain overnight.

New research led by scientists at UCLA Health and Tel Aviv University
provides the first physiological evidence from inside the human brain supporting the dominant scientific theory on how the brain consolidates
memory during sleep.

Further, the researchers found that targeted deep-brain stimulation
during a critical time in the sleep cycle appeared to improve memory consolidation.

The research, published June 1 in Nature Neuroscience, could offer
new clues for how deep-brain stimulation during sleep could one day
help patients with memory disorders like Alzheimer's disease, said
study co-author Itzhak Fried, MD, PhD. This was achieved by a novel "closed-loop" system that delivered electrical pulses in one brain region precisely synchronized to brain activity recorded from another region.

According to the dominant theory for how the brain converts new
information into long-term memories during shuteye, there's an overnight dialogue between the hippocampus -- the brain's memory hub -- and
the cerebral cortex, which is associated with higher brain functions
like reasoning and planning. This occurs during a phase of deep sleep,
when brain waves are especially slow and neurons across brain regions
alternate between rapidly firing in sync and silence.

"This provides the first major evidence down to the level of single
neurons that there is indeed this mechanism of interaction between the
memory hub and the entire cortex," said Fried, the director of epilepsy
surgery at UCLA Health and professor of neurosurgery, psychiatry
and biobehavioral sciences at the David Geffen School of Medicine
at UCLA. "It has both scientific value in terms of understanding how
memory works in humans and using that knowledge to really boost memory."
The researchers had a unique opportunity to test this theory of memory consolidation via electrodes in the brains of 18 epilepsy patients at
UCLA Health. The electrodes had been implanted in the patients' brains
to help identify the source of their seizures during hospital stays
typically lasting around 10 days.

The study was conducted across two nights and mornings. Just before
bedtime, study participants were shown photo pairings of animals and
25 celebrities, including easily identifiable stars like Marilyn Monroe
and Jack Nicholson.

They were immediately tested on their ability to recall which celebrity
was paired with which animal, and they were tested again in the morning
after a night of undisturbed sleep.

On another night, they were shown 25 new animal and celebrity pairings
before bedtime. This time, they received targeted electrical stimulation overnight, and their ability recall the pairings was tested in the
morning. To deliver this electrical stimulation, the researchers had
created a real-time closed- loop system that Fried likened to a musical conductor: The system "listened" to brain's electrical signals, and
when patients fell into the period of deep sleep associated with memory consolidation, it delivered gentle electrical pulses instructing the
rapidly firing neurons to "play" in sync.

Each individual tested performed better on memory tests following a
night of sleep with the electrical stimulation compared to a night of undisturbed sleep.

Key electrophysiological markers also indicated that information was
flowing between the hippocampus and throughout the cortex, providing
physical evidence supporting of memory consolidation.

"We found we basically enhanced this highway by which information flows
to more permanent storage places in the brain," Fried said.

Fried in 2012 authored a New England Journal of Medicine study that for
the first time showed that electrical stimulation can strengthen memory,
and his work has continued to explore how deep brain stimulation could
improve memory, now moving into the critical stage of sleep. He recently received a $7 million NIH grant to study whether artificial intelligence
can help pinpoint and strengthen specific memories in the brain.

"In our new study, we showed we can enhance memory in general,"
Fried said.

"Our next challenge is whether we have the ability to modulate specific memories." Yuval Nir of Tel Aviv University co-supervised the study
with Fried. Other authors include lead author Maya Geva-Sagiv, as well as
Emily Mankin, Dawn Eliashiv, Natalie Cherry, Guldamla Kalender and Natalia Tchemodanov from UCLA, and Shdema Epstein from Tel-Aviv University.

* RELATED_TOPICS
o Mind_&_Brain
# Memory # Intelligence # Neuroscience # Sleep_Disorders
# Brain-Computer_Interfaces # Dementia # Brain_Injury #
Disorders_and_Syndromes
* RELATED_TERMS
o Sleep o Memory-prediction_framework o
Circadian_rhythm_sleep_disorder o Rapid_eye_movement o Memory
o Limbic_system o Bruxism o Delayed_sleep_phase_syndrome

========================================================================== Story Source: Materials provided by University_of_California_-_Los_Angeles_Health_Sciences.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Maya Geva-Sagiv, Emily A. Mankin, Dawn Eliashiv, Shdema Epstein,
Natalie
Cherry, Guldamla Kalender, Natalia Tchemodanov, Yuval Nir,
Itzhak Fried.

Augmenting hippocampal-prefrontal neuronal synchrony during sleep
enhances memory consolidation in humans. Nature Neuroscience,
2023; DOI: 10.1038/s41593-023-01324-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230601155923.htm

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