FIG. 5.
The interaction of synaptic input and electrical coupling in controlling the activity of model motor neurons. Simultaneous bilateral records of membrane potential (Vm: pink, peristaltic; blue, synchronous), total synaptic current (ISynTotal, green), coupling current (Icoup, orange), summed synaptic and coupling current (Isum, black), and absolute phase (φ) in HE(3) and HE(8) model motor neuron pairs. Corresponding currents are directly above (peristaltic) or below (synchronous) the membrane potential traces and approximately one heartbeat cycle is shown. A and B illustrate current and voltage records with (standard value of coupling) and without electrical coupling, respectively. Electrical coupling tends to synchronize the burst activity of the motor neurons and its effect is strongest when the synaptic inhibition from the premotor cells overlaps. See text for further explanation. The red dashed line and arrow indicate the level of outward current that suppresses spike activity in the model motor neurons (Fig. 2B).