Robust Short-Term Memory without Synaptic Learning

Short-term memory in the brain cannot in general be explained the way long-term memory can – as a gradual modification of synaptic weights – since it takes place too quickly. Theories based on some form of cellular bistability, however, do not seem able to account for the fact that noisy neurons can collectively store information in a robust manner. We show how a sufficiently clustered network of simple model neurons can be instantly induced into metastable states capable of retaining information for a short time (a few seconds). The mechanism is robust to different network topologies and kinds of neural model. This could constitute a viable means available to the brain for sensory and/or short-term memory with no need of synaptic learning. Relevant phenomena described by neurobiology and psychology, such as local synchronization of synaptic inputs and power-law statistics of forgetting avalanches, emerge naturally from this mechanism, and we suggest possible experiments to test its viability in more biological settings.This work was supported by Junta de Andalucía projects FQM-01505 and P09-FQM4682, by the joint Spanish Research Ministry (MEC) and the European Budget for the Regional Development (FEDER) project FIS2009-08451, and by the Granada Research of Excellence Initiative on Bio-Health (GREIB) traslational project GREIB.PT_2011_19 of the Spanish Science and Innovation Ministry (MICINN) “Campus of International Excellence.” S.J. is grateful for financial support from the Oxford Centre for Integrative Systems Biology, and from the European Commission under the Marie Curie Intra-European Fellowship Programme PIEF-GA-2010-276454