Differential Resilience to Perturbation of Circuits with Similar Performance*

Experimental work on the crustacean stomatogastric ganglion (STG) shows a 2-6 fold variability in the expression of ion channel and receptor genes and in the conductance densities for many of the processes that are important for circuit dynamics. Old and new computational work with conductance-bases single neurons and small network models shows that similar network performance can arise from diverse underlying parameter sets. Together, these lines of evidence suggest that each individual animal, at any moment in its life-time, has found a different solution to producing “good enough” motor patterns for normal behavior. This poses the question of the extent to which animals with different sets of underlying circuit parameters can respond reliably and robustly to environmental perturbations and neuromodulation. Consequently, we study the effects of temperature, pH and neuromodulation on the pyloric rhythm of crabs. While all animals respond remarkably well to large environmental perturbations, extreme perturbations that produce system "crashes" reveal the underlying parameter differences in the population. Studies of multiple computational models with similar behaviors under control conditions reveal interesting dynamics when perturbed.