Figure 6.
Reduction of a spike-based model to a rate-based model. The spike model defines a relationship between presynaptic and postsynaptic spike trains through a function S. The rate model defines a relationship between rates through a function f. Rates are related to spikes through an observation function R. Reduction is possible when the diagram commutes: the composition of R and S equals the composition of f and R (mathematically, R o S = f o R). This is not generally possible because R is not invertible (many spike trains have the same rate).