Psychology

NU-led study observes memory storage during sleep

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Playing and listening to sound while sleeping may rather reinforce learning, a Northwest-led study released in October concluded.

Led by Jessica Creery (Weinberg ’15, Ph.D.’19), a former graduate student at NU’s Cognitive Neuroscience Laboratory, the study examined memory consolidation – the process by which new memories are stored in the brain and converted into lasting memories. , long memories. term memories.

Researchers from the psychology departments of the University of Michigan and Middlebury College, as well as the departments of neurology and neurological surgery at the University of Chicago, participated in the study.

“WWe’re just at the tip of the iceberg in understanding how memory is processed,” Creery said.

In the study, Creery asked nine patients to learn the locations of a series of objects on a screen, each associated with a unique sound. After a half-hour break, patients were tested for the location of each object, but were not given feedback on their answers.

The patients then slept while Creery played 10 to 20 sounds repeatedly — half of which related to the objects and their locations that each patient had memorized — and monitored the patient’s brain activity.

When patients were retested for the objects’ locations in the morning, their performance improved significantly compared to the pre-sleep test.

“When you present a sound to a patient, the hippocampus reacts differently if it’s one of the sounds they heard in the memory test,” said psychology professor Ken Paller, a senior investigator on the study and director of the Cognitive Neuroscience Program. “Part of that activity is associated with an improvement in their ability to remember the location (of the object) when they wake up in the morning.”

The study is the first to use electrodes in the brain to observe memory processing during sleep, Paller said.

The electrodes allowed researchers to record brain activity directly from the hippocampus and cerebral cortex, which had previously only been observed in animals.

However, Creery said her team did not implant the electrodes themselves.

We were only able to do that because patients already had electrodes implanted in their brains,” Creery said. “They had medically intractable epilepsy and their neurology team identified the area of ​​seizure onset.”

However, due to overnight seizure activity, four of the nine patients were excluded from the results of the study.

Sixth-year Psychology Ph.D. student Adrianna Bassard worked on the study and said the implanted electrodes allowed the team to record more accurate results.

“If we’re monitoring from the scalp, we can only really see what stage of sleep you’re in,” Bassard said. “If someone has electrodes implanted in their brain, we can see more precisely tuned oscillations.”

The study improved understanding of memory consolidation by linking improvements in memory to both sound reactivation and specific brain activity patterns, Paller said.

Because those patterns of brain activity occur specifically during sleep, researchers also said the study demonstrates the importance of sleep for memory stabilization.

“A lot of people neglect their sleep because they think it’s just a waste of time,” Paller said. “But for memories, for creativity, for problem solving, we need to value our sleep a little more.”

E-mail: [email protected]

Twitter: @joyycee.li

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