Fig 4. Third-order cumulant contributions to plasticity can be broken down into four terms.

A. The first term contains all the α-, β- and γ-paths originating from the source neuron k to the spiking neurons i and j. B-D. The other terms take into account the possibility of an intermediate neuron l that acts as a new source neuron for two of the paths. These are referred to as ‘branched paths’, and the path length from the source neuron k to the intermediate neuron l is denoted with ζ. The branching describes the individual terms in Eq 5.