Korean Researchers First in the World to Uncover Principles of Brain Memory Formation

KAIST Department of Biological Sciences Professor Han Jinhee's Team Reveals Principle of Memory Encoding in Neurons with Strengthened Synaptic Connections
Using Optogenetic Technology, First Demonstration of Memory Formation Principle Expected to Provide Clues for Dementia Treatment

[Asia Economy Reporter Kim Bong-su] The principle by which human brain cells store memories has been identified for the first time in the world by a domestic research team.

The Korea Advanced Institute of Science and Technology (KAIST) announced on the 13th that Professor Han Jin-hee's research team from the Department of Biological Sciences has elucidated the fundamental principle by which neurons encoding memories are selected within the complex neural network composed of countless neurons and synaptic connections between them.

Humans store past experiences in the brain in the form of memories and use them. It is known that memories are encoded and stored in a very small number of neurons throughout the brain. However, it has been uncertain whether these neurons are predetermined or selected according to some principle. Solving this question is academically very important as it clarifies how memories, one of the unresolved challenges in neuroscience, are formed in the brain, and it also provides clues for treating dementia, thus having enormous social and economic ripple effects.

Back in 1949, Canadian neuropsychologist Donald Olding Hebb proposed the idea of synaptic plasticity in his book The Organization of Behavior, suggesting that if two neurons are activated simultaneously in time, the synaptic connection between these two neurons will be strengthened. Subsequent experiments proved that long-term potentiation (LTP) actually occurs at specific synapses through learning. However, until now, it had not been elucidated how LTP determines the neurons that encode memories.

To clarify the action of LTP, the research team used optogenetic technology to stimulate synapses in the amygdala region of mouse brains in specific patterns where LTP does not naturally occur under natural learning conditions. They artificially strengthened or weakened these synaptic connections and investigated whether the neurons encoding memories changed accordingly.

First, when the synapses were pre-stimulated to induce LTP before the mice experienced a fearful event, memories were encoded in these synapses that were originally unrelated to the memory, and neurons where LTP occurred participated selectively in memory encoding with a much higher probability compared to surrounding neurons. However, when these synapses were artificially stimulated again using optogenetics immediately after learning to weaken the synaptic connections, memories were no longer encoded in these synapses and neurons.

Conversely, when the synaptic connections were artificially strengthened through LTP stimulation immediately after the mice experienced a fearful event normally, it was surprisingly confirmed that fear memories were encoded in these synapses where LTP was manipulated and selectively encoded in the neurons where LTP was induced compared to other surrounding neurons. These results prove that while the memory itself does not change when synaptic strength is artificially manipulated, the neurons encoding that memory do change.

Professor Han Jin-hee said, “New connection patterns are created among neurons by LTP, and through this, a specific cell assembly related to experiences is newly formed in the brain,” adding, “We have elucidated that the formation of these strongly interconnected neurons is the principle by which memories are formed in the brain.”

The results of this study were published on the 24th of last month in Nature Communications, an open-access journal of the Nature Publishing Group.

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