Capacity analysis in multi-state synaptic models: a retrieval probability perspective

  • Authors:
  • Yibi Huang;Yali Amit

  • Affiliations:
  • Department of Statistics, University of Chicago, Chicago, USA 60637;Departments of Statistics and Computer Science, University of Chicago, Chicago, USA

  • Venue:
  • Journal of Computational Neuroscience
  • Year:
  • 2011

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Abstract

We define the memory capacity of networks of binary neurons with finite-state synapses in terms of retrieval probabilities of learned patterns under standard asynchronous dynamics with a predetermined threshold. The threshold is set to control the proportion of non-selective neurons that fire. An optimal inhibition level is chosen to stabilize network behavior. For any local learning rule we provide a computationally efficient and highly accurate approximation to the retrieval probability of a pattern as a function of its age. The method is applied to the sequential models (Fusi and Abbott, Nat Neurosci 10:485---493, 2007) and meta-plasticity models (Fusi et al., Neuron 45(4):599---611, 2005; Leibold and Kempter, Cereb Cortex 18:67---77, 2008). We show that as the number of synaptic states increases, the capacity, as defined here, either plateaus or decreases. In the few cases where multi-state models exceed the capacity of binary synapse models the improvement is small.