海角社区

Memory is central to our identity鈥攂ut in Alzheimer鈥檚 disease, the ability to form new long-term memories fades, often long before older memories begin to erode. While researchers have extensively studied the hippocampus, the brain鈥檚 short-term memory center, and the neocortex, its vast long-term archive, the crucial middle player between them鈥攖he entorhinal cortex鈥攔emains poorly understood.

鈥淲e know the entorhinal cortex is the most severely affected brain region in early Alzheimer鈥檚, yet we know surprisingly little about what it actually does,鈥� said Dr. Juhee Haam, assistant professor in 海角社区鈥檚 Department of Biological Sciences. 鈥淢ost people鈥攁nd even many scientists鈥攈aven鈥檛 heard of it. If we want to understand why patients struggle to form new memories, we need to understand this region.鈥�

Sitting between the hippocampus and neocortex, the entorhinal cortex acts like a transfer station. If the hippocampus is your computer鈥檚 RAM and the neocortex its hard drive, the entorhinal cortex is the hub that moves memories from short-term to long-term storage.

But it鈥檚 not a one-way street鈥攖his region also enables two-way communication between the hippocampus and neocortex during memory consolidation. Exactly how these circuit pathways work, however, remains unknown.

Discovering a Key Brain Rhythm for Memory Formation

Dr. Haam鈥檚 research centers on a previously unknown rhythmic brain signal in the entorhinal cortex, where she recently discovered delta oscillations in a specialized group of neurons called the temporoammonic (TA) pathway.

Her lab was the first to show that . Through experiments that disrupted this brain rhythm, she found that mice had trouble navigating environments they had already learned, such as remembering the location of a hidden platform in a water maze. Although other brain signals were functioning normally, the impaired TA delta oscillations significantly hindered their ability to form new memories.

Now, supported by a new five-year, $1.8 million NIH R01 grant, Dr. Haam鈥檚 team will investigate how these TA delta rhythms coordinate the exchange of information between brain regions鈥攅specially during sleep, when memories are consolidated.

Using advanced techniques such as in vivo electrophysiology, optical recording of TA delta oscillations, and behavioral testing, the team aims to clarify how TA delta rhythms influence hippocampal memory signals, how neocortical inputs modulate the entorhinal cortex, and how these interactions integrate new experiences into the broader memory network.

鈥淓very new memory isn鈥檛 formed as an isolated orb, like in the movie Inside Out,鈥� Haam explained. 鈥淭hey鈥檙e not filed away like perfect boxes on a shelf鈥攅ach one is shaped by what you already know.鈥� She points out that if every memory were stored independently, the brain would quickly run out of capacity. 

Unlike Pixar's Inside Out, where memories sparkle as colorful marbles that either roll off into storage or zip back to "Headquarters" for Joy, Sadness, and the others to debate, real memory relies on vast, interconnected brain networks working together. New memories must be integrated with existing knowledge to keep our memory system efficient. The entorhinal cortex collaborates with the neocortex and hippocampus to determine how and where these memories fit, influencing what we retain and how we recall it. 

This process, called memory integration, helps explain why two people can share the same experience yet remember it differently, depending on which prior memories and details stand out to them. 

With support from the NIH grant, Haam鈥檚 team aims to uncover how this integration happens at the neural level. By mapping how the entorhinal cortex coordinates the brain鈥檚 memory network, they hope to reveal principles that apply not only to Alzheimer鈥檚 disease but to memory function across the entire human lifespan.

鈥淭his is not just about Alzheimer鈥檚,鈥� Haam said. 鈥淚t鈥檚 about how every person forms and shapes memories based on who they already are. Memory is a fundamental part of human cognition鈥攁nd we鈥檙e finally starting to understand how it works.鈥�