Linking structure and activity in nonlinear spiking networks
Fig 13
Construction of Feynman diagrams for the first nonlinear correction to the two-point cumulant (graphs containing one loop).
In each panel, we add a new layer of vertices to the diagrams, until we arrive at a source vertex. When there are multiple potential ways to add vertices, we add diagrams to account for each of those constructions. A) External vertices corresponding to the two measurement times, with incoming propagator (Δ) edges. B) Diagrams with one internal vertex added. t1 ↔ t2 corresponds to switching the two external vertices in the bottom diagram; the top diagram is symmetric with respect to that switch. C) Diagrams with two layers of vertices. The top diagram finishes that of B, top. The second two arise from the second diagram of B, and each also have copies with t1 ↔ t2. D) Last diagrams containing one loop. The final diagrams corresponding to the one-loop correction to the second cumulant are the top two of C) and that of D).