<P> A pair of parietal ganglia lie along the length of the main nerve cords, supplying nerves to the gill and associated olfactory organ . Because of the torsion of the nerve cords, one parietal ganglion is typically higher in the body than the other . Finally, the nerve cords terminate in a linked pair of visceral ganglia, which supply nerves to the remaining organs of the visceral mass . </P> <P> A study, published in 2016 in Nature, has shown that in air - breathing freshwater snails of the genus Lymnaea Lamarck, 1799 goal - directed decision - making during the hunt for food is performed by just two neuron types . Through measuring the action potentials between neurons, the researchers found that just two neurons were able to come to a complicated form of decision making . One neuron in the brain tells the snail if food is nearby, the second neuron signals whether the snail is hungry or not . Such decision making helps the snail save energy by reducing complex brain activity when there is no food nearby and adapts its behavior in the absence of food . Thus the snail can switch between a low - use mode and a high - use mode depending on the decision . According to lead researcher György Kemenes, this could help engineers design more efficient "robot brains" in future . </P> <P> Neurons of Helix, Helix aspersa, are used for study of epileptogenesis, because they are sensistive to epileptogenic drugs including pentylenetetrazol . </P>

Define the nervous system of mollusca animal pila