Fig. 8.

Schematic diagram summarizing the responses of swim circuit neurons during shortening. All of the identified swim-activating, gating, and oscillator interneurons are shown. For the sake of clarity, the only synaptic connections displayed are those that are known to link adjacent functional levels in H. medicinalis (Friesen, 1989a; Brodfuehrer et al., 1995b); the ⊥ symbol indicates an excitatory synapse. The feedback from the oscillator to the gating level is not represented in this diagram [with the exception of an identified synapse from cell208 to cell 21 (Nusbaum, 1986), the synaptic basis of this feedback is not known]. Cell 33is less darkly shaded than cells 204 and208, because it is inhibited more weakly and with longer latency. Cells 123, 60, and 27 are shown with dotted outlines because these cells, which are difficult to locate and identify, were not tested.