Neural Mechanisms underlying Evolvability of Behavior

Georgia State University Research Foundation, Inc., Atlanta GA

Investigators

Abstract

This project examines fundamental questions about the features of neural circuits that affect the evolution of behavior. The species being examined are nudibranch sea slugs, which have highly accessible nervous systems that allow experiments to be conducted that are not feasible in other types of animals. The brains of nudibranchs contain only about 10,000 nerve cells (neurons), many of which can be individually identified from animal to animal within a species. Furthermore, neurons can often be identified across different species. Electrical activity can be recorded from multiple neurons to reveal neural circuitry. The connectivity of those circuits can be compared across species. This research team found that although the species have the same sets of neurons, they are wired up differently, even when the species produce similar behaviors. One goal of the project is to artificially rewire the neurons in one species to produce the neural circuit of another species and to create mathematical models that do the same. This will establish how easy it is to convert the behavior of one species into that of another. It also contributes to understanding the basic rules for generating behavior by comparing across species instead of focusing on a single species. The project engages the public by soliciting observations of nudibranch behavior from divers around the world through social media. It also provides important research opportunities to under-represented students through a research pipeline and creates resources that will be available to the scientific community to aid in identifying neurons and mapping out circuits. Evolvability reflects the ability to evolve. This project examines the features of neural circuits that affect the evolvability of swimming behaviors in nudibranchs. The project uses a variety of techniques to achieve its goals. First, transcriptomics is used to resolve the phylogeny of the Nudibranchia and allow phylogenic hypotheses to be tested. The brain transcriptomes further aid in the discovery of molecular markers for identified neurons, which are needed particularly in species that do not swim. Electrophysiological techniques are used to search for "latent" circuitry, that is, connectivity that might be present in non-swimmers and potentially activated by small changes. These changes will be applied using the dynamic clamp technique to inject artificial synaptic and membrane conductances and through ectopic expression of serotonin receptors. Finally, mathematical simulations are used to examine the consequences of different circuit architectures and their robustness for rhythmic activity.