Newfound 'Switchboard' Helps the Brain Form New Memories Without Forgetting Older Ones

Findings May Offer Blueprint for Smarter, More Flexible AI Systems

NEW YORK, June 3, 2026 /PRNewswire/ -- The brain may reuse some cells to store many different memories without mixing them up with or erasing older memories, a new study in mice suggests. 

Led by NYU Langone Health researchers, the study revealed that about one in four memory cells in a brain area called the hippocampus acts as a shared "hub" that links incoming and outgoing signals.

A report on the findings was published online May 13 in the journal Nature.

Scientists have long wondered how the brain can be flexible enough to learn new information while also being stable enough not to forget past knowledge.

To shed light on this mystery, the investigators focused on a chain of connected areas linking the hippocampus, which sits deep inside the brain and helps organize new experiences into memories, and the neocortex, the brain's outer layer, which stores long-term information. These included the cornus ammonis 3 (CA3), a hippocampal region that sends in fast-changing information; cornus ammonis 1 (CA1), a hippocampal region that acts as a central hub; and the retrosplenial cortex, which plays a key role in navigation and scene reconstruction.

The team found that a minority of hippocampal CA1 cells (neurons) carry most of the incoming messages that were sent by CA3. Then, when CA1 sends signals to the retrosplenial cortex, those same cells fire in a different pattern, creating a separate outgoing channel.

In this way, messages coming in and going out stay separate even though they reuse many of the same neurons, much like how an electronic switchboard can manage many calls without crossing the lines. This setup may help the retrosplenial cortex maintain its map's stability while the other two regions continue learning from experience.

"Our findings help explain how memory can be both moldable and enduring," said study co-lead author Joaquín Gonzalez, PhD, a postdoctoral fellow in the Department of Psychiatry at NYU Grossman School of Medicine. "By changing how the same cells fire together instead of turning on new cells, the brain can keep information organized and protect older memories." 

Additional findings showed that the key CA1 neurons that handle daytime communication remain active at night during sleep, in brain events known as sharp-wave ripples.

Because the same core of cells handles both daytime processing and nighttime replay, the pathway from hippocampus to cortex can remain open and help solidify memories.

"Our study shows how learning and memory consolidation can coexist in the same network," said study co-lead author Mihály Vöröslakos, MD, PhD, a postdoctoral fellow in NYU Grossman School of Medicine's neuroscience department. "Our discovery was made possible because for the first time, we were able to record hundreds of individual neurons across all the key regions simultaneously in animals that were moving around naturally."

"Our discovery of a 'memory switchboard' deep in the hippocampus may provide clues as to how memory circuits fail in Alzheimer's disease and other conditions that affect the brain's ability to recall events and find places," said study co-senior author Zhe S. Chen, PhD, a professor in the Departments of Psychiatry and Neuroscience at NYU Grossman School of Medicine.

For the study, the research team trained six mice to run back and forth on a straight track with water rewards at each end. While the animals explored, the scientists used high-density electrodes to record activity from hundreds of neurons at once. They also tracked the rodents' positions so they could match each spike of brain activity with the mouse's behavior at that moment.

The team then looked for shared patterns of activity between regions to see how signals from CA3 were transformed by CA1 before reaching the retroplenial cortex. In additional sessions, the researchers recorded the mice while they slept and found that the waking patterns were replayed many times but differently within the hippocampus and across the hippocampus and neocortex.

According to the authors, these findings may help address a major challenge faced by artificial intelligence tools, which tend to 'forget' what they have learned when trained on new tasks.

"By showing how the mammalian brain can safeguard memories during learning, our research may offer a biological blueprint for designing next-generation AI technology that can update itself continuously without overwriting what it has already acquired," said study co-senior author György Buzsáki, MD, PhD, the Biggs Professor of Neuroscience at NYU Grossman School of Medicine and a member of NYU Langone's Institute for Translational Neuroscience.

Dr. Buzsáki, who is also a member of NYU Grossman School of Medicine's Department of Neurology, said that the researchers' next plan is to examine whether similar switchboardlike channels appear in other memory circuits.

Because the study was conducted in mice in a controlled environment, the researchers cannot draw firm conclusions about what happens in more natural environments or in the human brain, cautioned Dr. Buzsáki.

Funding for the study was provided by National Institutes of Health grants RF1DA056394, P50MH132642, R01MH122391, and U19NS107616.

Along with Drs. Gonzalez, Vöröslakos, Chen, and Buzsáki, NYU Langone researchers involved in the study were Deren Aykan; Nina Soto, PhD; Noam Nitzan, PhD; Rachel Swanson, PhD; and Mursel Karadas, PhD.

About NYU Langone Health
NYU Langone Health is a fully integrated health system that consistently achieves the best patient outcomes through a rigorous focus on quality that has resulted in some of the lowest mortality rates in the nation. Vizient Inc. has ranked NYU Langone No. 1 out of 118 comprehensive academic medical centers across the nation for four years in a row, and U.S. News & World Report recently ranked four of its clinical specialties number one in the nation. NYU Langone offers a comprehensive range of medical services with one high standard of care across seven inpatient locations, its Perlmutter Cancer Center, and more than 320 outpatient locations in the New York area and Florida. The system also includes two tuition-free medical schools, in Manhattan and on Long Island, and a vast research enterprise.

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SOURCE NYU Grossman School of Medicine and NYU Langone Health