A recent study has uncovered that the recollection of a particular experience is stored in several parallel ‘copies.’ These copies are preserved for different lengths of time, altered to varying extents, and sometimes even erased as time passes.
Transforming our experiences into memories enables us to learn from the past, guiding us on how to approach new situations effectively. Thus, as our environment changes, this memory system cannot remain just a static repository of nostalgic moments. Instead, it must be adaptable, evolving with time and new circumstances to enhance our ability to foresee future events and choose the best responses. The mechanisms by which the brain manages these dynamic memories were unclear until the discovery of multiple memory copies.
Professor Flavio Donato and his research group at the Biozentrum of the University of Basel are studying how memories are stored in the brain and how they evolve throughout an individual’s life, using mouse models for their experiments. They have revealed that in the hippocampus—a brain region pivotal for learning from experience—one single event is represented by parallel memory copies found in at least three distinct groups of neurons, which develop at different stages during embryonic growth.
Memory copies shift and evolve over time
The earliest neurons to develop play a crucial role in the long-term retention of memories. Initially, these memory copies might be too weak for the brain to access, but they gain strength as time progresses. Even in humans, the brain may only be able to access such memories after some time has elapsed since their encoding.
On the other hand, the memory copy created by the neurons that develop later is initially robust but diminishes over time; thus, with enough time, this copy can become inaccessible to the brain. A more stable memory copy can be found in the neurons that emerge between the two extremes during development.
Interestingly, the choice of memory copy utilized may be linked to how easily a memory can be altered or employed to forge a new one. The memories formed shortly after an event by late-born neurons can be revised or rewritten. This suggests that recalling a situation soon after it occurs activates the late-born neurons, allowing current information to blend with the original memory. Conversely, recalling the same event after a significant period primes the early-born neurons, reactivating their copy, but the associated memory becomes less amenable to modification. “The dynamic nature of memory storage in the brain showcases its plasticity, which is fundamental to its vast memory capacity,” states first author Vilde Kveim.
Adaptable memories support suitable behavior
Professor Donato’s team has consequently shown that which memory copy is activated and the timing of that activation can significantly influence how we remember, alter, and utilize our memories. “The brain faces an impressive challenge regarding memory. It not only needs to recall past events to help us understand our world but also to adapt to ongoing changes, thus ensuring our memories remain relevant for making informed future decisions,” explains Flavio Donato.
Maintaining persistence through dynamic processes is a delicate balancing act, and we may now have an opportunity to deepen our understanding of it. The researchers aspire that, with a better understanding of the factors influencing memory encoding and modification in the brain, they could help alleviate memories that become pathologically intrusive or potentially recover those that we thought were irretrievably lost.
Transforming experiences into memories allows us to learn from earlier actions and use those lessons as templates for navigating new situations. Hence, in a constantly evolving world, our memory system should not be a static repository of past moments. Instead, it should remain dynamic, evolving with time and adjusting to fresh contexts to optimally aid us in predicting future outcomes and making the best choices. The ways in which the brain manages these memory dynamics were previously mysterious—but the discovery of multiple memory copies has shed light on the matter.
