"We use a computational model of a hippocampal CA1 pyramidal cell to demonstrate that spine
head calcium provides an instantaneous readout at each synapse of the postsynaptic weighted
sum of all presynaptic activity impinging on the cell. The form of the readout is equivalent
to the functions of weighted, summed inputs used in neural network learning rules. Within a
dendritic layer, peak spine head calcium levels are either a linear or sigmoidal function of
the number of coactive synapses, with nonlinearity depending on the ability of voltage spread
in the dendrites to reach calcium spike threshold. ..."
Graham BP, Saudargiene A, Cobb S (2014) Spine head calcium as a measure of summed postsynaptic activity for driving synaptic plasticity. Neural Comput 26:2194-222 [PubMed]