Physics Colloquium: Neural Structure, Function and Dynamics in C. Elegans

The Department of Physics is pleased to welcome Dr. Andrew Leifer for an in-person colloquium. Andrew M. Leifer, Ph.D., is an Assistant Professor of Physics and Neuroscience at Princeton University. He obtained a B.S. in Physics and B.A. in Political Science at Stanford University and earned his Ph.D. in Biophysics from Harvard University under the guidance of Professor Aravinthan Samuel. He then received a Lewis Sigler Fellowship to form his own independent research group at Princeton University, where he subsequently joined the faculty in 2016. Dr. Leifer’s laboratory uses novel optical methods to manipulate and monitor brain-wide neural activity during movement in the nematode C. elegans to reveal the interplay between neural dynamics, neural connectivity, and animal behavior.  He is also an investigator in the Simons Collaboration on the Global Brain and a recipient of the National Science Foundation’s CAREER Award and the National Institute of Health’s New Innovator Award.

Abstract

The nematode C. elegans’ small nervous system of 302 neurons and its completely mapped anatomical wiring, or connectome, make it a powerful model for systems neuroscience. Yet even with this granular anatomical description, it remains challenging to accurately predict brain wide neural dynamics or detailed circuit function because it is unknown for many neural connections how signals propagate from one neuron to the next. To fill this gap, we created a comprehensive neural response map of the C. elegans head at cellular resolution by measuring network calcium activity in response to single-neuron optogenetic perturbations for more than 10,000 neuron-pairs. We captured the sign (excitatory or inhibitory), strength, temporal properties, and the causal direction of signal propagation between neurons. We find that signal propagation in the brain differs from what anatomy predicts. Moreover, simulations constrained by our functional measurements better agree with spontaneous dynamics than do simulations constrained by anatomy. We find that extrasynaptic signaling, including via neuropeptides, is one mechanism underlying this divergence of structure and function.   Because neuropeptide machinery is widely expressed in many nervous systems, our findings may have broader implications for structure-function relations in other organisms.