Research reveals how dendrites connect brain memories

If you've ever noticed how memories of the same day are connected while events apart are feeling separate weeks, a new study will reveal why.

This finding comes from a mouse study, and researchers observed memory formation using advanced imaging techniques, including miniature microscopes that captured single cell resolution in living animals.

This study shows that memory is preserved in dendritic areas. Once one memory is formed, the affected dendrites are prepared to capture new information arriving within the next few hours, linking the memory formed in time.

When you think of neurons as computers, the dendrites are like small computers within them, each performing their own calculations. This finding shows that we can link information that our brains arrive in time for the same dendritic location and expand our understanding of how memories are organized. ”

Assistant Professor of Psychology at Ohio State University, lead author, Mega Segall

This study was recently published in a journal Natural Neuroscience.

While most learning and memory studies focus on how a single memory is formed in the brain, Sehgal's lab aims to determine how multiple memories are organized.

“The idea is that we don't form memories on our own. You don't form a single memory. You use that memory, create a framework for memories, and pull from that framework when you need to make adaptive decisions,” she said.

Neurons, the main brain cells, are known to encode and relay information. Dendrites – branch-like projections extending from neurons – play an important role in how information is processed, receiving incoming information and passing it over to the neuronal cell body.

However, dendrites are more than just passive conduits. Each dendrite can function as an independent unit of calculation. Dendrites have been thought to play an important role in brain function, but how it shapes learning and memory has previously become unclear, Saegal said.

When mice were exposed in the experiment to two different environments in a short period of time, the team found that memories of these spaces were linked. If mice received mild shocks in one of these spaces, the animals frozen out of fear in both environments and associated shocks from one room with the other.

This study focused on the brain retros cortex (RSC), a brain region essential for spatial and contextual memory. The researchers observed that linked memories were consistently involved with RSC neurons and their dendritic branches in the same group.

The team tracked these changes at the dendritic level by visualizing small dendrite processes, dendritic spines, to which neurons communicate. The formation of new memory caused the addition of clustered dendritic spines. This is an important process for enhancing communication between neurons and promoting learning.

The spinal clusters of dendrites formed after the first memory are likely to attract new spines during the second, intimate timing memory, and physically link these experiences in the brain.

The team used optogenetics to confirm the role of dendrites in linking memories. This is a technique that allows researchers to control neurons with light. By reactivating specific dendritic segments that were active during memory formation, we have otherwise been able to link irrelevant memories, further demonstrating the importance of dendritic changes in memory network formation.

In addition to revealing the previously unknown role of dendrites in linking memories, the findings pave the new pathway to understanding memory-related disorders, Segal said.

“Our work not only broadens our understanding of how memories are formed, but also suggests exciting new possibilities for manipulating higher-order memory processes,” she said. “This could have an impact on developing treatments for memory-related conditions such as Alzheimer's.”

Sehgal has led the research in collaboration with Alcino Silva, director of UCLA's Integrated Centre for Integrated Learning and Memory, and Panayiota Poirazi, research director at the Research and Technology Research Foundation in Greece.

This work was supported by the National Institutes of Mental Health, the National Institutes of Aging, Dr. Miriam, Sheldon G. Adelson Foundation for Medical Research, European Commission, National Institutes of Health, and the Einstein Foundation Berlin.