A model of a segmental oscillator in the leech heartbeat neuronal network

We modeled a segmental oscillator of the timing network that paces the hear tbeat of the leech. This model represents a network of six heart interneuro ns that comprise the basic rhythm-generating network within a single gangli on. This model builds on a previous two cell model (Nadim et al., 1995) by incorporating modifications of intrinsic and synaptic currents based on the results of a realistic waveform voltage-clamp study (Olsen and Calabrese, 1996). Due to these modifications, the new model behaves more similarly to the biological system than the previous model. For example, the slow-wave o scillation of membrane potential that underlies bursting is similar in form and amplitude to that of the biological system. Furthermore, the new model with its expanded architecture demonstrates how coordinating interneurons contribute to the oscillations within a single ganglion, in addition to the ir role of intersegmental coordination.