Biological Neurons Are Different From Neural Networks: Simulating C.elegans in an open science project

The membrane potential of a biological neuron is considered to be one of the most importantproperties to understand its dynamic state. While the action potential or discrete “spike” featureof mammalian neurons has been emphasized as an information bearing signal, biologicalevidence exists that even without action potentials, neurons process information and give rise todifferent behavioral states. Nowhere is this more evident than in the nematode worm C.elegans , where its entire nervous system of 302 neurons, despite a lack of action potentials,organizes complex behaviors such as mating, predator avoidance, location of food sources, andmany others. For thirty years, the C. elegans nervous system has remained the only adult animal that has hadits nervous system connectivity mapped at the level of individual synapses and gap junctions.As part of the international open science collaboration known as OpenWorm, we have built a1simulation framework, known as c302, that enables us to assemble the known connectivity andother biological data of the C. elegans nervous system into a Hodgkin­Huxley­based simulationthat can be run in the NEURON simulation engine. Using a physical simulation of the C. elegans body, known as Sibernetic, we have injected simple sinusoidal activation patterns of the muscle cells of the C. elegans and produced simplecrawling and swimming behavior. With the goal of producing the same simple sinusoids in themuscle cells, we have used c302 to select a subnetwork from the full C. elegans nervoussystem and used machine learning techniques to fit dynamic parameters that are underspecifiedby the data. Our preliminary results still leave many important biological features out, butinitially demonstrate that it is possible to make motor neurons produce sinusoidal activitypatterns in the muscles as used in the physical simulation.

In this talk I will discuss these initial results and discuss future directions for a betterunderstanding of the information processing underlying the C. elegans’ nervous system.