“Why do patients with dementia and cognitive decline continue to be stuck in past memories?” Researchers at KAIST have become the first in the world to identify the existence of a “neural switch” in the brain that selectively recalls the most recent memories. This study reveals the principle by which the brain selects necessary information between past and new memories, and offers new possibilities for future treatments for memory decline and cognitive inflexibility.
On May 17, KAIST announced that a research team led by Professor Han Jin-hee of the Department of Biological Sciences has discovered, for the first time in the world, that a specific neural circuit that connects the medial septum (MS, a brain region that controls memory and learning) and the medial entorhinal cortex (MEC, a brain region connected to the hippocampus that processes memory information) plays an important role in switching between past and recent memories and selecting the most recent and appropriate information. Because of the situation.
We live our lives by refreshing our memories through new experiences every day. For example, if the restaurant you visited today was more satisfying than the restaurant you visited yesterday, your brain will modify your existing memory to reflect the new information. The ability to select the necessary information between past and present memory is thus central to higher cognitive functions such as decision making, problem solving, future prediction, and logical reasoning. However, the mechanism by which the brain differentiates and switches between memories has remained unclear for a long time.
The research team focused on the medial septum, located deep in the brain. The medial septum regulates the rhythm of hippocampal activity and acts as a “conductor” that helps the brain store and retrieve information effectively.
The study found that when certain neurons in the medial septum send signals to the medial entorhinal cortex, an area of the brain that processes memory information and delivers it to the hippocampus, the brain can better recall recent memories.
Conversely, when the researchers used light to artificially interrupt this neural circuit, the experimental animals were no longer able to use up-to-date information and began behaving according to past patterns. Neural activity in the hippocampus, which plays an important role in memory representation, also returned to its past state. This suggests that this circuit functions as a “neural switch” that selects the latest information needed for the current situation from among multiple memories.
The research team also analyzed memory performance depending on the state of brain activity. Our brains cycle between an “online state” where we actively process information (theta waves, brain waves that appear when we are learning or concentrating) and an “offline state” where we are at rest (delta waves, slow brain waves that appear when we sleep or rest).
The analysis found that the longer a person remained online, the better they recalled recent memories, while frequent switching between online and offline states significantly reduced memory retrieval ability. This suggests that specific brain rhythms and states are important neurobiological indicators that determine effective memory recall.
This research is significant in that it reveals how the brain flexibly reflects new information while maintaining past memories. The research team hopes that this discovery may lead to the development of new therapeutic techniques to improve memory loss and cognitive flexibility in patients with degenerative brain diseases such as dementia and Alzheimer’s disease.
This research presents a new paradigm for understanding the principle by which our brain organizes and utilizes a large number of experiences in chronological order. He added, “Until now, memory retrieval was understood simply as the replay of stored traces, but through this study we demonstrate that the brain has a control system that actively selects the most recent information from competing memories.”
KAIST Faculty of Biological Sciences Professor Han Jin-hee
Dr. Kim Moo-joon of KAIST’s School of Biological Sciences and doctoral students Boin Seo, Seo Seung-hoi, Choi Jong-wook, Hwang Jae-min, and Park Ju-hee participated in this research, which was published in a magazine on April 29. natural neurosciencea top international journal in neuroscience.
This research was supported by the Mid-Career Research Program (National Research Foundation of Korea), the Samsung Science and Technology Foundation, and the KAIST Jang Yong-sil Fellow Program.
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KAIST (Korea Advanced Institute of Science and Technology)
Reference magazines:
Kim, M. others. (2026). The septal entorhinal GABAergic pathway allows switching between episodic memories. natural neuroscience. DOI: 10.1038/s41593-026-02280-6. https://www.nature.com/articles/s41593-026-02280-6
