Summary diagram illustrating the known interactions between the swim activating and inactivating systems in the head ganglion and the swim generating network (swim gating and oscillatory interneurons) in the segmental nerve cord . In our model, the swim activating and inactivating systems affect the swim g enerating network in a parallel, but opposite manner. Some interactions are ba sed upon previous studies (Nusbaum et al., 1987 and Brodfuehrer et al., 1993a ). Symbols: T-junction = excitatory interaction; ball and stick junction = inhibitory interaction; plus arrowhead = yet identified excitatory inputs and minus arrowhead = yet identified inhibitory inputs.