Abstract
Long-term memories are likely stored in the synaptic weights of neuronal networks in the brain. The storage capacity of such networks depends on the degree of plasticity of their synapses. Highly plastic synapses allow for strong memories, but these are quickly overwritten. On the other hand, less labile synapses result in long-lasting but weak memories. Here we show that the trade-off between memory strength and memory lifetime can be overcome by partitioning the memory system into multiple regions characterized by different levels of synaptic plasticity and transferring memory information from the more to less plastic region. The improvement in memory lifetime is proportional to the number of memory regions, and the initial memory strength can be orders of magnitude larger than in a non-partitioned memory system. This model provides a fundamental computational reason for memory consolidation processes at the systems level.
Highlights
Memories are stored and retained through a series of complex, highly coupled processes that operate on different timescales
The process of memory consolidation starts at the level of individual synaptic connections, but it involves circuit reorganization in multiple brain regions
We show that there is a computational advantage in partitioning memory systems into subsystems that operate on different timescales
Summary
Memories are stored and retained through a series of complex, highly coupled processes that operate on different timescales. It is widely believed that after the initial encoding of a sensory-motor experience, a series of molecular, cellular, and system-level alterations lead to the stabilization of an initial memory representation (memory consolidation). Some of these alterations occur at the level of local synapses, while others involve the reorganization and consolidation of different types of memories in different brain areas. Studies of patient HM revealed that medial temporal lobe lesions severely impair the ability to consolidate new memories, whereas temporally remote memories remain intact [1]. Memory lifetimes are extended by a factor that is proportional to the number of memory stages
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