This connection implements a complex synapse model as described in:

Ziegler, L., Zenke, F., Kastner, D.B., and Gerstner, W. (2015). Synaptic Consolidation: From Synapses to Behavioral Modeling. J. Neurosci. 35, 1319–1334. Fulltext:http://www.jneurosci.org/content/35/3/1319

The code of the model (Connection object) is available here https://github.com/idiot-z/zynapse