A recent study that recently appeared in Sciences, claims that memories of specific experiences are stored in several simultaneous “copies.” These are maintained for varying amount of time, updated to some extent, and occasionally wiped, according to the scientists at the University of Basel. The ability to converts into memories proceed us to learn from the pasts and use those lessons as a foundation for responding appropriately in new situations. As a result, as the world around us changes, our memories system can’t be restricted to serving as a static archive of past. Rather, it must be dynamic, changing with time and adapting to new circumstances to help us make better predictions about the future and decide on the must appropriate course of action.
Hippocampal neurons that are born at different stages of embryonic development divide into subpopulations with the unique genetic, morphological, and functional characteristics. These subpopulations are preferentially link across subdivisions. We proposed the theory that dynamic features and long-term persistence of memories could be conferred by selective activation of unique neuronal subpopulation at particular periods of the memory’s history. Thus in conjunction with hippocampus-dependent associative learning paradigms, we utilized a variety of techniques to record and manipulate the activity of hippocampal neurons associated with particular dates of birth in order to analyse the role played by birth dated subpopulations in the encoding, persistence, and temporal evolution of a memory.
When a contextual fear memory is learnt and recalled, a methodical mapping of the recruitment of developmentally defined subpopulations to memory ensembles shows that neurons formed early or late neurogenesis have different recruitment trajectories following encoding. Early born neurons were preferentially recruited at later times, while late born neurons were preferentially recruited for retrieval at short latency following acquisition, these differing paths replicated the dynamics of reactivation captured by long term calcium imaging studies, which also disclosed different network-wide reactions across subpopulations. Learning was linked to a plastic reconfiguration of coactivity dynamics and functional connectivity in the late-born subnetwork, while learning did not alter the more rigidly organized activity patterns of the early born neurons.
The brain has an amazing task when it comes to remembering. To help us make sense of the world we live in, it must, on the one hand, remember what has happened in the past. However, in order to support us in making decisions that are right for the future, it and our memories bot need to adjust to changes that are occurring in our environment, “explains Donato.
We may now have a thorough understanding of the complex balancing act that is persistence through dynamics. The scientists hope that one day, by learning more about the processes that lead to memories being encoded and altered in the brain, they will be able to either soften or restore memories that we previously believed to be lost forever.
Reference
Vilde A. Kveim et al, Divergent recruitment of developmentally defined neuronal ensembles supports memory dynamics, Science (2024). DOI: 10.1126/science.adk0997.
