This talk was by organizer Paul Katz and covered a wide range of topics. He started with some past successes of gastropod neuroscience, e.g. electrophysiology and behavior in reduced preparations. Before, new individual neurons and their location/characterization could be published. Nowadays, mapping the nervous system has largely become a database problem. One model system for mapping neurons in the Tritonia central pattern generator (CPG) for swimming. As with the other gastropod model systems, you can take the brain of Tritonia out and record the behavior in the isolated nervous system and the neurons can be individually identified. Similar to many other gastropd systems, serotonin has a strong modulatory effect on the properties and synaptic strenghts within the swimming CPG of Tritonia. This intrinsic neuromodulation by serotonin is state-dependent.
In a great evolutionary comparison, Paul then went on to talk about homologous neurons in two swimming snails, one that swims by flexing dorso-ventrally (Tritonia) and one the flexes laterally (Melibe). Do these homologous swim-interneurons perform the same functions in animals that swim by flexing the body differently? It turns out that the CPG organization is fundamentally different, in that electrical coupling and synaptic inhibition are exactly turned by 90° between both species, meaning that dorsoventral swimmers synchronize their lateral sides, whereas lateral swimmers synchronize their dorsoventral sides with electrical coupling. Serotonergic modulation of the CPGs is also different in both species. At the end of this comparison, Paul showed us a bunch of other, more or less related swimming and non-swimming species and their homologous neurons within the evolutionary tree. He concludes that the different swimming modes must have arisen several times independently in these snail species.