Spring 2016
Seminars are held at 11:30AM in Cullimore Hall, Room 611, unless noted otherwise. For questions about the seminar schedule, please contact Casey Diekman.
Date: March 29, 2016
Speaker: Patrick Fletcher
Laboratory of Biological Modeling,
National Institutes of Health
Title: "From Global to Local: Exploring the Relationship Between Parameters and Behaviors in Models of Electrical Excitability"
Abstract:
Models of electrical activity in excitable cells involve nonlinear interactions between many ionic currents. Changing parameters in these models can produce a variety of activity patterns with sometimes unexpected effects. Furthermore, introducing new currents will have different effects depending on the initial parameter set. We combine global sampling of parameter space and local analysis of representative parameter sets in a pituitary cell model to understand the effects of adding K+ conductances, which mediate some effects of hormone action on these cells. Global sampling ensured that the effects of introducing K+ conductances were captured across a wide variety of contexts of model parameters. For each type of K+ conductance we determined the types of behavioral transition that it evoked. Some transitions were counterintuitive, and may have been missed without the use of global sampling. In general, the wide range of transitions that occurred when the same current was applied to the model cell at different locations in parameter space highlight the challenge of making accurate model predictions in light of cell-to-cell heterogeneity. Finally, we used bifurcation analysis and fast/slow analysis to investigate why specific transitions occur in representative individual models. This approach relies on the use of a graphics processing unit (GPU) to quickly map parameter space to model behavior and identify parameter sets for further analysis. Acceleration with modern low-cost GPUs is particularly well suited to exploring moderately-sized parameter spaces of excitable cell and signaling models.