The lab is interested in understanding how neuronal circuits operate. We are focussing on simple circuits in opisthobranch molluscs, in particular, the nudibranch, Tritonia diomedea. Our research examines how the actions of a set of identified serotonergic neurons are integrated into the central pattern generator (CPG) underlying escape locomotion in this animal. The work funded by grants for the National Institute of Neurological Disease and Stroke (NINDS) and National Institute of Mental Health (NIMH) at the National Institutes of Health (NIH) and a grant from the National Science Foundation (NSF) as well as local funding from Brains & Behavior and the Center for Behavioral Neuroscience.
One project is to examine timing-dependent and state-dependent forms of neuromodulation or heterosynaptic plasticity. We have found that the serotonergic dorsal swim interneurons (DSIs) in Tritonia have different effects on the strength of synapses made by another member of the CPG, the ventral swim interneuron (VSI-B), depending upon when those neurons are stimulated with respect to each other and depending upon the state of the VSI synapse at the time that DSI was active. We are currently investigating the mechanism underlying this novel form of neuromodulation. We are conducting calcium imaging studies to determine how calcium signaling contributes to serotonergic neuromodulation and motor pattern generation. In collaboration with William Frost of the Rosalind Franklin University School of Medicine, we have created computer models of the swim circuit. To enable a complete exploration of parameter space, we developed a tool in the NEURON simulation environment called NeuronPM.
Another project in the lab is examining the evolution of the swim circuit. We have identified homologues of the DSIs in sevaral other opisthobranchs, including Aplysia californica and Melibe leonina. Aplysia does not swim and Melibe swims by a completely different method (lateral body flexions instead of dorsal/ventral flexions). The DSI homologs have different functions in the different species. We have also found that homologous neurons in species with similar behaviors can also have different functions. A phylogenetic analysis suggests that even when homologous neurons serve the same function, this could be caused by independent evolution.
Through the Brains & Behavior initiative, we have a collaboration with Sushil Prasad, Raj Sunderraman and Ying Zhu in the Computer Science Department to build NeuronBank: a database of identified neurons. This database will serve as a repository of knowledge about the organization of nervous systems. It will also allow us to more rapidly identify neurons and connections and facilitate the identification of homologous neurons in related species. This project was initiated by a seed grant from Brains and Behavior and support from NSF
modified December 10, 2010