Competition for a limited supply of synaptic building blocks predicts multiplicative synaptic normalization and heterosynaptic plasticity

Abstract

We present a mathematical model of synaptic normalization and heterosynaptic plasticity based on competition for limited synaptic resources. In the model, afferent synapses on a part of the dendritic tree of a neuron compete for a limited supply of synaptic building blocks such as AMPA receptors or other postsynaptic components, which are distributed across the dendritic tree. These building blocks form a pool of parts that are ready for incorporation into synapses. Using minimal assumptions, the model produces fast multiplicative normalization behavior and leads to a homeostatic form of heterosynaptic plasticity. It therefore supports the use of such rules in neural network models. Furthermore, the model predicts that the amount of heterosynaptic plasticity is small when many building blocks are available in the pool. The model also suggests that local production and/or assembly of postsynaptic building blocks across the dendritic tree may be necessary to maintain a neuron's proper function, because it facilitates their homogeneous distribution across the dendritic tree. Because of its simplicity and analytical tractability, the model provides a convenient starting point for the development of more detailed models of the molecular mechanisms underlying different forms of synaptic plasticity.