Cedars-Sinai researchers have discovered how brain cells responsible for working memory (the type needed to remember a phone number long enough to dial it) coordinate intentional focus and short-term information storage.
The study detailing their discovery was published in the peer-reviewed journal. Nature.
“We have identified for the first time a group of neurons, influenced by two types of brain waves, that coordinate cognitive control and the storage of sensory information in working memory,” said Jonathan Daume, PhD, a postdoctoral researcher in the Rutishauser Laboratory of Cedars-Sinai and first author of the study. “These neurons do not contain or store information, but are crucial for the storage of short-term memories.”
Working memory, which requires the brain to store information for just a few seconds, is fragile and requires sustained focus to maintain, said Ueli Rutishauser, PhD, director of the Center for Neural Sciences and Medicine at Cedars-Sinai and lead author of the study. . It can be affected by different diseases and conditions.
“In disorders like Alzheimer’s disease or attention-deficit/hyperactivity disorder, the problem is often not memory storage, but the ability to focus and retain a memory once it has been formed,” said Rutishauser, professor of Neurosurgery, Neurology and Biomedical Sciences at Cedars-Sinai. “We believe that understanding the control aspect of working memory will be critical to developing new treatments for these and other neurological conditions.”
To explore how working memory works, researchers recorded the brain activity of 36 hospitalized patients who had electrodes surgically implanted in their brains as part of a procedure to diagnose epilepsy. The team recorded the activity of individual brain cells and brain waves while the patients performed a task that required the use of working memory.
On a computer screen, patients were shown a single photograph or a series of three photographs of various people, animals, objects, or landscapes. The screen then went blank for just under three seconds, forcing patients to remember the photos they had just seen. They were then shown another photo and asked to decide whether it was the one (or one of the three) they had seen before.
When patients performing the working memory task were able to respond quickly and accurately, the researchers noted the activation of two groups of neurons: “category” neurons that fire in response to one of the categories shown in the photographs. , like animals, and “phase” neurons. -Amplitude coupling”, or PAC, neurons.
PAC neurons, newly identified in this study, do not contain any content, but use a process called phase-amplitude coupling to ensure that category neurons focus and store the content they have acquired. PAC neurons fire at the same time as the brain’s theta waves, which are associated with concentration and control, as well as gamma waves, which are related to information processing. This allows them to coordinate their activity with category neurons, which also simultaneously fire gamma waves in the brain, improving patients’ ability to recall information stored in working memory.
“Imagine that when the patient sees a photo of a dog, his category neurons start firing ‘dog, dog, dog’ while his PAC neurons fire ‘focus/remember,'” Rutishauser said. “Through phase-amplitude coupling, the two groups of neurons create harmony by overlapping their messages, resulting in ‘remember the dog.’ It is a situation where the whole is greater than the sum of its parts, like listening the musicians of an orchestra to play together. The conductor, like the PAC neurons, coordinates the different musicians so that they act in harmony.
PAC neurons do this work in the hippocampus, a part of the brain that has long been known to be important for long-term memory. This study offers the first confirmation that the hippocampus also plays a role in working memory control, Rutishauser said.
This study was conducted as part of a multi-institutional consortium funded by the National Institutes of Health. Brain research by advancing innovative neurotechnologies Initiative, or The BRAIN Initiative, and led by Cedars-Sinai. Data from this study are combined between Cedars-Sinai, the University of Toronto, and Johns Hopkins School of Medicine, resulting in a statistically powerful study that a single institution could not amass on its own given the difficulty of these experiments.
“One of the goals of the BRAIN Initiative is to discover, through the use of innovative technologies, properties of the human brain that until now have been difficult, if not impossible, to study,” said Dr. John Ngai, PhD, director. from the NIH BRAIN Initiative. “Here, by taking advantage of unusual opportunities supported by the initiative to illuminate complex processes in humans, the Rutishauser Laboratory is shedding light on how certain neurons support how memories are stored in the brain, a process that is far from understood in disorders devastating brain diseases such as Alzheimer’s disease and other dementias.