We study how memories are physically represented in the brain. Our lab helped pioneer the idea of engrams—groups of neurons that store a specific memory. We have shown that not all neurons are equally likely to become part of an engram: more excitable neurons tend to “win” and are more likely to be recruited. These rules shape how memories are organized in the brain, including how different experiences become linked. We also study how these processes break down in conditions such as acute stress and neurodegenerative diseases like Alzheimer’s, leading to memory problems.

New memories are fragile at first. Over time, they become more stable and long-lasting through a process called consolidation. Early on, many memories depend on the hippocampus, but with time they are reorganized and stored in the cortex. Our lab has identified brain circuits and mechanisms that support this long-term storage and allow memories to be retrieved weeks, months, or even years later. We also study how this reorganization affects the quality and detail of memories.

Children and young animals forget experiences more quickly than adults, a phenomenon known as infantile amnesia. Using animal models and clinical populations, we have shown that high levels of new neuron growth in the developing hippocampus contribute to this faster forgetting. We also study how memories formed early in life differ from adult memories in their precision. Our recent work shows that developmental increases in memory accuracy depend on changes in brain structure and inhibitory circuits.

While neurons are central to memory, they do not work alone. We are increasingly focused on the role of other brain cell types, including oligodendrocytes, astrocytes, and microglia. For example, we have shown that myelination—the process by which axons are insulated—is important for forming long-lasting memories. Ongoing work explores how these non-neuronal cells support memory stability and long-term maintenance.