is then rapidly extended, and this is usually followed by directed swimming. The LGI is one of the few examples of a true command neuron. It passes the necessity and sufficiency principle put forward by Kupfermann and Weiss. Wiersma's initial experiments showed that direct stimulation of the LGI was a sufficient release for the tail flip. In 1981, it was Olson and Krasne who showed that the LGI fulfilled the condition of necessity, because when spikes were inhibited in the LGI through introducing a hyperpolarizing current, no motor activity was produced in response to a stimulus that would have originally elicited the tail flip. The LGI contains the following three phases, occurring over the span of about 100 ms: 1 – Flexion production The LGI receives its sensory input from the hair-like projections found on the edge of the tail fan. The sensory information is sent from bipolar receptors connected to the hair that are directionally sensitive. The path of the signal varies from here depending on the strength of the input. In the beta pathway, the signal can then pass a chemical synapse, the information is sent to a sensory interneuron (SI) of either type A (which fires phasically in response to input) or type C, (which fire tonically). From there, the signal is sent across an electrical synapse to the LGI. The LGI can also receive the sensory input directly through an electrical synapse by way of the alpha pathway. This bypasses the SIs. The LGI can pass the signal to the MoG's by two paths one of which passes the signal to the Motor Giant through direct electrical synapses. The MoG then passes the signal to the FF muscles. It can also use a second route across a fast electrical synapse to a premotor interneuron called the segmental giant (SG), two of which are located in each segment. The SGs then relays the signal to fast flexor motor neurons. The end result is a powerful and rapid flexion. The convergence many inputs on the LGI and divergence of few signals show how the LGI functions as a decision making coincidence detector. It takes the information from both the alpha and the beta pathways and if the timing of the spikes is synchronous, the behavior is produced. If the timing is asynchronous, the later input is blocked by reducing the driving force of the signal and increasing the