Eluding oblivion with smart stochastic selection of synaptic updates

Fusi, Stefano; Senn, Walter (2006). Eluding oblivion with smart stochastic selection of synaptic updates. Chaos, 16(2), p. 26112. Melville, N.Y.: American Institute of Physics 10.1063/1.2213587

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The variables involved in the equations that describe realistic synaptic dynamics always vary in a limited range. Their boundedness makes the synapses forgetful, not for the mere passage of time, but because new experiences overwrite old memories. The forgetting rate depends on how many synapses are modified by each new experience: many changes means fast learning and fast forgetting, whereas few changes means slow learning and long memory retention. Reducing the average number of modified synapses can extend the memory span at the price of a reduced amount of information stored when a new experience is memorized. Every trick which allows to slow down the learning process in a smart way can improve the memory performance. We review some of the tricks that allow to elude fast forgetting (oblivion). They are based on the stochastic selection of the synapses whose modifications are actually consolidated following each new experience. In practice only a randomly selected, small fraction of the synapses eligible for an update are actually modified. This allows to acquire the amount of information necessary to retrieve the memory without compromising the retention of old experiences. The fraction of modified synapses can be further reduced in a smart way by changing synapses only when it is really necessary, i.e. when the post-synaptic neuron does not respond as desired. Finally we show that such a stochastic selection emerges naturally from spike driven synaptic dynamics which read noisy pre and post-synaptic neural activities. These activities can actually be generated by a chaotic system.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Physiology

UniBE Contributor:

Senn, Walter

Subjects:

600 Technology > 610 Medicine & health

ISSN:

1054-1500

ISBN:

16822044

Publisher:

American Institute of Physics

Language:

English

Submitter:

Factscience Import

Date Deposited:

04 Oct 2013 14:45

Last Modified:

20 Jun 2016 10:12

Publisher DOI:

10.1063/1.2213587

PubMed ID:

16822044

Web of Science ID:

000238729600041

URI:

https://boris.unibe.ch/id/eprint/18526 (FactScience: 712)

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