Fig. 9.

Depressing synapses mediate bistability in a symmetric model. A computational model consisting of two identical neurons reciprocally connected via two depressing synapses was constructed. Both model neurons lacked autorhythmic properties but expressed post-inhibitory rebound. Shown are voltage traces of the two neurons. Horizontal dotted lines indicate the midpoint of the depression/recovery curve at −67 mV. With no synaptic connections, the two neurons were quiescent with a membrane potential of −44 mV. When the maximal conductances of both synapses were set to 1 mS/cm² (first arrow), after a small perturbation in neuron B, the two neurons produced alternating rhythmic activity (CD mode). At the time indicated by the left bar, a 200 msec current pulse of −10 μA/cm² was injected into neuron B. This caused the rhythm to switch from CD mode to SC mode. At the time indicated by the right bar, a 1500 msec current pulse of +10 μA/cm² was injected into neuronB. This caused the rhythm to switch back to the CD mode.