A cellular mechanism for systems memory consolidation

Ever since patient H.M. - arguably the most famous case study in neuroscience - we know that damages of a specific region of the brain, the hippocampus, causes a loss of memories for recent events while preserving memories of events from the distant past. Declarative memories are therefore only transiently dependent on the hippocampus, and appear to be gradually transferred into cortical networks. This process - termed "systems memory consolidation" - apparently takes place during sleep and is thought to be essential for long-term memory retention. Its cellular or systems level implementation, however, is still far from clear.

In my talk, I will suggest a novel mechanism for the consolidation of memories from hippocampus to cortex. I will posit that the full consolidation process consists of a cascade of small consolidations steps, which gradually increase memory lifetime. In each step, memories are copied from one set of synapses to another by a combination of spike timing-dependent plasticity - a form of synaptic plasticity that is widely found in the brain - and a generic anatomical network motif that is also prominent throughout the nervous system. I will use theoretical arguments and simulations to first illustrate the mechanism in one of these consolidation steps, and then show that a hierarchical iteration of the same principle i) consistent with lesion studies and ii) can lead to power-law forgetting, i.e. to long memory retention times (as already suggested by Roxin and others). I will close by discussing that the same mechanism could also serve for the consolidation of other forms of memory (such as perceptual or motor learning) and as a generic mechanism that simplifies information flow in cortical networks.