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Synaptic and nonsynaptic plasticity approximating probabilistic inference

Tully, Philip, 1988- (author)
KTH,Beräkningsbiologi, CB,Stockholm Brain Institute, Stockholm; University of Edinburgh
Hennig, Matthias (author)
University of Edinburgh
Lansner, Anders (author)
KTH,Beräkningsbiologi, CB,Stockholm Brain Institute, Stockholm; Stockholm University
 (creator_code:org_t)
2014-04-08
2014
English.
In: Frontiers in Synaptic Neuroscience. - : Frontiers Media SA. - 1663-3563. ; 6:APR
  • Journal article (peer-reviewed)
Abstract Subject headings
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  • Learning and memory operations in neural circuits are believed to involve molecular cascades of synaptic and nonsynaptic changes that lead to a diverse repertoire of dynamical phenomena at higher levels of processing. Hebbian and homeostatic plasticity, neuromodulation, and intrinsic excitability all conspire to form and maintain memories. But it is still unclear how these seemingly redundant mechanisms could jointly orchestrate learning in a more unified system. To this end, a Hebbian learning rule for spiking neurons inspired by Bayesian statistics is proposed. In this model, synaptic weights and intrinsic currents are adapted on-line upon arrival of single spikes, which initiate a cascade of temporally interacting memory traces that locally estimate probabilities associated with relative neuronal activation levels. Trace dynamics enable synaptic learning to readily demonstrate a spike-timing dependence, stably return to a set-point over long time scales, and remain competitive despite this stability. Beyond unsupervised learning, linking the traces with an external plasticity-modulating signal enables spike-based reinforcement learning. At the postsynaptic neuron, the traces are represented by an activity-dependent ion channel that is shown to regulate the input received by a postsynaptic cell and generate intrinsic graded persistent firing levels. We show how spike-based Hebbian-Bayesian learning can be performed in a simulated inference task using integrate-and-fire (IAF) neurons that are Poisson-firing and background-driven, similar to the preferred regime of cortical neurons. Our results support the view that neurons can represent information in the form of probability distributions, and that probabilistic inference could be a functional by-product of coupled synaptic and nonsynaptic mechanisms operating over several timescales. The model provides a biophysical realization of Bayesian computation by reconciling several observed neural phenomena whose functional effects are only partially understood in concert.

Keyword

Bayes' rule
synaptic plasticity and memory modeling
intrinsic excitability
naïve Bayes classifier
spiking neural networks
Hebbian learning
Computer Science
Datalogi
Teoretisk kemi och biologi
Theoretical Chemistry and Biology
Biological Physics
Biologisk fysik

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art (subject category)

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