Connection is one of the three abstract base classes of Auryn. It implements synaptic connections in Auryn. In its basic function Connection objects take spikes from a SpikingGroup (source) and deliver them to a destination of type NeuronGroup. It implements the transmit() function used to add spike induced quantities to certain neuronal state variables. Which state variable is affected is determined via the set_transmitter() member function, which is implemented here as well. Connection has the important purely virtual member function propagate() which is called for each Connection instance in each simulation time step.