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Michael
P. Nusbaum, Ph.D.
Professor, Dept of Neuroscience
Chair, Neuroscience Graduate Group
School of Medicine
120 Johnson Pavilion
(215) 898-1585 FAX: (215) 573-9050
email: nusbaum@mail.med.upenn.edu
Click here for selected publications since Dr. Nusbaum's arrival at Penn
RESEARCH INTERESTS
Neural network modulation; motor pattern selection from multifunctional
networks; local, presynaptic influences; neuropeptide function, cotransmission,
sensory influence on central neuronal networks RESEARCH TECHNIQUES
Intrasomatic and intra-axonal recordings, extracellular recordings, intracellular dye injections, neurotransmitter immunocytochemistry; exogenous application of modulatory transmitters; confocal microscopyRESEARCH SUMMARY
We aim to understand how the nervous system selects and generates distinct motor patterns from multifunctional neural networks. The current set of issues that we are addressing include (1) the cellular mechanisms underlying how different identified modulatory projection and sensory neurons elicit distinct outputs from the same neural circuits, including the role of coreleased small molecule and neuropeptide transmitters in this process, and (2) how distinct but related neural circuits interact to generate a coordinated output. We use a small model system, the stomatogastric nervous system (STNS), which is an extension of the CNS in decapod crustaceans that controls the rhythmic movements of different regions of the foregut underlying various aspects of feeding. The STNS consists of 4 ganglia, containing several distinct but interacting rhythmically active circuits that control the different foregut regions. The two motor patterns that we study (called the pyloric and gastric mill rhythms) are generated by overlapping sets of neurons located in the stomatogastric ganglion (STG), which contains only 26 neurons in our experimental animal, the crab Cancer borealis. There are many advantages to studying this preparation for obtaining a cellular-level understanding of neuronal circuit function. All of the STG neurons are readily recorded intracellularly, they are all physiologically identified, their intraganglionic synapses and many of their membrane properties are known, and so are their neurotransmitters. More than a dozen modulatory transmitters have been localized as inputs to the STG from the other STNS ganglia. When individually bath applied, many of these transmitters elicit distinct pyloric and gastric mill rhythms. Individual activation of different projection and sensory neurons also elicits distinct rhythms. We are using a set of identified projection and sensory neurons to study the above-mentioned issues. We are also assessing the relationship between the circuit response to bath application of individual modulatory transmitters and to activation of modulatory neurons containing the same transmitter. Our analysis also includes identifying and determining the function of "presynaptic inputs" occurring on the STG terminals of these projection neurons. These presynaptic inputs are electrically invisible in the ganglion of origin of these neurons, so we study them by recording from these neurons intra-axonally, at the entrance to the STG. Results from work with the STNS has led to general principles of neural circuit dynamics that have been extended to many other systems, ranging from other invertebrates to the mammalian systems.
KEY WORDS:
Neuromodulation; neural networks; neuropeptides; identified neurons; cotransmission
The Nusbaum Lab
Matt Kirby, Rachel White, Mike Nusbaum, Nick Delong, Dawn Blitz, Lingli Zhang, Aaron Cook
