Complex computation in a small neural network.

The computational abilities of the central nervous system of the terrestrial mollusc Limax maximus are described, based on results of associative conditioning studies of both intact animals and isolated nervous systems. It was found that postingestive conditioning to amino acid deficient diets is a particularly robust form of associative learning, with memory retention clearly demonstrated for 127 days. Immunocytochemical localization of two neurotransmitters important to the feeding control system modified by learning (FMRFamide and gamma-aminobutyric acid) is presented. Additional approaches to localizing critical cell groups and synaptic sites involved in learning and memory storage are presented.