Our memories are not static; they evolve throughout our lives, changing as we learn, experience new things, and recall them repeatedly. Additionally, memory function deteriorates with age. Previously, scientists believed that this malleability was due to changes in the brain cells that initially encoded the memory, with each memory being stored as a single copy. However, new research suggests a more complex picture.
Scientists have discovered that in rodents, the brain stores at least three copies of a memory, encoded in different locations within the hippocampus, a brain region crucial for learning and memory. These copies are encoded by distinct groups of neurons and differ in their creation time, longevity, and modifiability over time.
In a study published in the journal *Science*, researchers observed that as mice encode new memories, they create three types of neurons:
1.
Early-born neurons
: These neurons store a long-term copy of the memory that is initially weak but strengthens over time.2.
Middle-ground neurons
: These neurons exhibit greater stability from the outset.3.
Late-born neurons
: These neurons initially encode very strong copies of a memory, but their strength fades over time.The researchers uncovered these findings by examining neuronal activity in the hippocampus after mice completed memory tasks, such as learning to avoid harmful situations. The different time scales at which these three groups of neurons operate may explain how the brain regulates memories over time.
The study revealed that memories stored by late-born neurons were more plastic (malleable) than those stored by early-born neurons. This suggests that early memories are more stable, while later memories are more susceptible to modification by new information.
If this phenomenon applies to humans, it could pave the way for new therapies for specific disorders. For example, in post-traumatic stress disorder (PTSD), individuals experience intrusive memories. A potential treatment could involve a drug that preferentially activates late-born neurons, making them more receptive to psychotherapy.
Similarly, for individuals with memory loss due to dementia, a drug could stimulate early-born neurons, whose data is stored more rigidly. These treatments would manipulate memory properties by selectively targeting specific neuron types involved in memory encoding.
This research offers exciting possibilities for understanding and manipulating memory, potentially leading to treatments for memory disorders and enhancing our understanding of the brain’s complex workings.
