KAIST Identifies Brain's 'Neural Switch,' Offering Clues for Treating Memory and Cognitive Decline

Humans constantly store new memories based on new experiences. In particular, the ability to "select necessary memories and information" between the past and present plays a crucial role in enabling high-level cognitive functions such as decision-making, problem-solving, and logical reasoning. A Korean research team has, for the first time in the world, identified a type of "neural switch" in the brain that distinguishes and switches between memories, offering clues for the treatment of memory loss and related conditions.

(From left) Professor Jinhee Han, Dr. Mujun Kim. KAIST

On May 18, KAIST announced that the research team led by Professor Han Jinhee from the Department of Biological Sciences has, for the first time in the world, identified that a specific neural circuit connecting 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 a key role in switching between past and present memories and selecting information according to context.

The medial septum, located deep within the brain, acts as a "facilitator" by regulating the rhythmic activity of the hippocampus, allowing the brain to store and retrieve information effectively.

The research team found that when specific neurons in the medial septum send signals to the medial entorhinal cortex—which processes and transmits memory information to the hippocampus—the brain activates recent memories. Conversely, when this neural circuit was artificially blocked using light, experimental animals were unable to utilize recent memories and instead behaved according to past patterns.

The neural activity in the hippocampus, which plays a critical role in memory storage, also reverted to a previous state. This demonstrates that the neural circuit functions as a "neural switch" that selects the information necessary for the present situation from among multiple memories.

This ability to select the necessary information between past and present memories is fundamental to high-level cognitive functions such as human decision-making, problem-solving, future prediction, and logical reasoning. The research team has thus demonstrated the principle by which the brain distinguishes and switches between memories, a question that had remained unresolved for a long time.

Selective regulation of past and present memories by the MS-MEC inhibitory neural circuit switch (AI-generated image). KAIST

The research team also analyzed memory performance according to the activation state of the brain. The human brain repeatedly alternates between an "online state" (theta waves, which are activated during learning and concentration) that processes information and an "offline state" (delta waves, slow brain waves observed during sleep or rest).

The analysis showed that the longer the online state is maintained, the clearer the memory becomes, while frequent transitions between the online and offline states significantly reduce memory retrieval ability. This suggests that specific brain rhythms and states serve as important neurological indicators for effective memory retrieval.

This research is significant in that it has revealed the mechanism by which the brain maintains past memories while flexibly integrating new information. The research team expects that this discovery will lead to the development of new treatment technologies to improve memory loss and cognitive flexibility decline in patients with degenerative brain diseases such as dementia and Alzheimer's disease.

Professor Han commented, "Through this study, our team discovered the principle by which the human brain organizes and utilizes countless experiences in chronological order. Unlike the traditional understanding that memory retrieval is simply a process of replaying stored traces, this research proves that the brain possesses an active 'regulatory system' that selects necessary information from competing memories."

This research involved Dr. Kim Mujun, doctoral candidates Seo Bo-in, So Seonhoe, Choi Jeong-uk, Hwang Jae-min, and Park Juhui—all graduate students in the Department of Biological Sciences at KAIST. The results were recently published in the international neuroscience journal 'Nature Neuroscience.'

This content was produced with the assistance of AI translation services.