Scientists find hidden layers in brain's memory center

Researchers at the Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI) at the Keck School of Medicine of USC have uncovered a previously unrecognized organizational pattern in one of the brain's key regions for learning and memory. According to findings reported in Nature Communications, the CA1 section of a mouse's hippocampus contains four separate layers of specialized cell types. The hippocampus plays an essential role in forming memories, guiding spatial navigation, and influencing emotions, and the discovery of these layers offers new insight into how information moves through this part of the brain. It also provides clues about why some cell types are especially vulnerable in conditions such as Alzheimer's disease and epilepsy.

"Researchers have long suspected that different parts of the hippocampus' CA1 region handle different aspects of learning and memory, but it wasn't clear how the underlying cells were arranged," said Michael S. Bienkowski, PhD, senior author of the study and assistant professor of physiology and neuroscience and of biomedical engineering.

"Our study shows that CA1 neurons are organized into four thin, continuous bands, each representing a different neuron type defined by a unique molecular signature. These layers aren't fixed in place; instead, they subtly shift and change in thickness along the length of the hippocampus. This shifting pattern means that each part of CA1 contains its own mix of neuron types, which helps explain why different regions support different behaviors. This may also clarify why certain CA1 neurons are more vulnerable in conditions like Alzheimer's disease and epilepsy: if a disease targets one layer's cell type, the effects will vary depending on where in CA1 that layer is most prominent."

High-resolution RNA imaging reveals cellular distinctions

To examine this structure, the research team used an RNA labeling technique called RNAscope together with high-resolution microscopy. This