A New Theory on Memory Storage in the Brain
According to a new theory presented by researchers at HHMI’s Janelia Research Campus and their colleagues at University College London, how useful a memory is for future situations determines where it resides in the brain.
The theory offers a new way of understanding systems consolidation, a process that transfers certain memories from the hippocampus – where they are initially stored – to the neocortex — where they reside long term.
Under the classical view of systems consolidation, all memories move from the hippocampus to the neocortex over time. But this view doesn’t always hold up; research shows some memories permanently reside in the hippocampus and are never transferred to the neocortex.
In recent years, psychologists proposed theories to explain this more complicated view of systems consolidation, but no one has yet figured out mathematically what determines whether a memory stays in the hippocampus or whether it is consolidated in the neocortex.
A Mathematical Approach to Understanding Memory Consolidation
Now, Janelia researchers are putting forward a new, quantitative view of systems consolidation to help resolve this longstanding problem, proposing a mathematical neural network theory in which memories consolidate to the neocortex only if they improve generalization.
Generalizations are constructed from the reliable and predictable components of memories, enabling us to apply them to other situations. We can generalize certain features of memories to help us understand the world, like the fact that canyons predict the presence of water.
This is different from episodic memories — detailed recollections of the past that have unique features like an individual memory we have of hiking to a particular canyon and coming upon a body of water.
Under this view, consolidation doesn’t copy memories from one area of the brain to another but rather creates a new memory that is a generalization of previous memories. The amount that a memory can be generalized – not its age — determines whether it is consolidated or remains in the hippocampus.
The researchers used neural networks to show how the amount of consolidation varies based on how much of a memory is generalizable. They were able to reproduce previous experimental patterns that couldn’t be explained by the classical view of systems consolidation.
The next step is to test the theory with experiments to see if it can predict how much a memory will be consolidated. Another important direction will be to test the authors’ models of how the brain might distinguish between predictable and unpredictable components of memories to regulate consolidation. Uncovering how memory works can help researchers better understand an integral part of cognition, potentially benefitting human health and artificial intelligence.
Reference: “Organizing memories for generalization in complementary learning systems” by Weinan Sun, Madhu Advani, Nelson Spruston, Andrew Saxe and James E. Fitzgerald, 20 July 2023, Nature Neuroscience.
DOI: 10.1038/s41593-023-01382-9
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2 Comments
Doesn’t it make sense that memories get “transferred” to the neocortex by being thought about? Neocortex based memories would be referential ones, intertwining perceptions of the original memory with references to related memories that it triggers, with higher connectivities for memories with more generalizability. Once the neocortextural memory is established, then the hippocampal memory won’t be likely to be triggered directly anymore. But memories that are suppressed because they’re traumatic don’t get transferred because re-experiencing them shuts off the analytical processes that wrap memories of thoughts with the raw memories (and thus transfer them to the neocortex.)
That is it. Memory is moved likely just thinking it. But memory is saved to synapses only temporarily.Permanent memory is saved to myelin sheats and oligodentrocytes associates mass memory entities together.
Memory is written as bit string of nitric oxide to microtubules protofilanents. The bit string is time function of action potentials. Bit string is saved under polymerization of microtubules. Under depolymerization the bit string is send bacwards to synapses, where it is polymerized again to MT tail. When tail is depolymerized the bit string is send upwards to MT inside myelin sheath and polymerized permanently.
When myelin sheath loosens all MT inside it relaxes, and the bit string bear Bose Einstein condensate which is consciousness.