Evolving Our Understanding of The Neural Control of Breathing Jeff Mendenhall College of William and Mary Department of Applied Sciences, Room #314

Outline Why Investigate Breathing Review Standard Model Shortcomings of the Standard Model The Next Step Dealing with the Problem of Detailed Models Where to from here

Our Motivation Necessity of breathing Stroke/Disease-induced lesions can impair breathing CCHS and other disorders of the control of breathing

Outline Why Investigate Breathing Review Standard Model Shortcomings of the Standard Model The Next Step Dealing with the Problem of Detailed Models Where to from here

System Overview Neural Control of Inspiration Takes Place in the preBötzinger Complex (preBötC) 1 preBötC XII Nerve Muscles

Terminology Inspiratory burst (raw) Inspiratory burst (smoothed) Inspiratory drive potential amplitude area

Outline Why Investigate Breathing Review Standard Model Shortcomings of the Standard Model The Next Step Dealing with the Problem of Detailed Models Where to from here

Standard Model Assumptions: Effectively Isospatial Currents Present: I NaP, I NaF, I K, I L, I tonic-e, I syn Predictions: “Pacemaker” neurons and I NaP Essential for Network-Level Bursts

Outline Why Investigate Breathing Review Standard Model Shortcomings of the Standard Model The Next Step Dealing with the Problem of Detailed Models Where to from here

Problems with the Standard Model I Assumptions: Effectively Isospatial Currents Present: I NaP, I NaF, I K, I L, I tonic-e + I CAN, I h, I A, I NMDA, I GABA

Problems with the Standard Model II Predictions: “Pacemaker” neurons and I NaP are Essential for Network Functioning -Pace, Mackay, Feldman, and Del Negro, J. Physiology, 582: Del Negro, Morgado-Valle. Mackay, and Feldman, J. Neuroscience, 25(2): Del Negro, Morgado-Valle, and Feldman, Neuron 34: ,

Outline Why Investigate Breathing Review Standard Model Shortcomings of the Standard Model The Next Step Dealing with the Problem of Detailed Models Where to from here

The Next Step I Correct Isospatial Assumption Use Realistic gNaP Conductance Dendritic Compartment Somatic Compartment Add Other Currents

The Next Step II Add mGluR-IP 3 -Ca 2+ -I CAN pathway

The Next Step III: Add material balance for Ca 2+ and Na + Example: Ca 2+ Balance

The Next Step IV Add calcium microdomains

Outline Why Investigate Breathing Review Standard Model Shortcomings of the Standard Model The Next Step Dealing with the Problem of Detailed Models Where to from here

The Problem: Too Many Poorly Constrained Parameters Dendritic Compartment Somatic Compartment

Methods: Evolving Solutions Step 2: Sit back, relax, let the computer do the work

Methods: Evolving Solutions Step 1: Teach the Fitness Function What is Important Score: 100 Score: -5 (Kill) Score: 40 Score: 50 Score: -30 (Kill) Fitness Function

What Is a Fitness Function Anyway? A weighted sum of fitness measures

Inside the Black Box Traces Scores Determine Kill Conditions Spike/Burst Analyzer Trace Statistics Surviving Traces Stable, Bounded Linear Regression Fitness Parameters

Advantages of Evolutionary Algorithm Efficiently Handles Large Parameter Spaces Yields Many Good Regions Approximates Their Boundaries

Preliminary Results Problem: Fit the current model to 4 experiment traces Number of Parameters: 110

Ideal Curve Some Evolved Solutions

Ca 2+ From Stores I CAN Ca 2+ (Dend) V (Dend)

Outline Why Investigate Breathing Review Standard Model Shortcomings of the Standard Model The Next Step Dealing with the Problem of Detailed Models Where to from here

Future Directions Add More Experiments Adjust Parameter Ranges Make / Test Predictions

Acknowledgements Academic Dr. Christopher Del Negro (C. W&M) Dr. Pete Roper (U. Utah) Financial NSF Grant IOB Suzzane Matthews Faculty Research Award

References 1.Smith, J.C., Ellenberger, H.H., Ballanyi, K., Richter, D.W. & Feldman, J.L. “Pre-Bötzinger complex: a brainstem region that may generate respiratory rhythm in mammals.” Science 254, (1991). 2.Rekling, J.C., Champagnat, J. & Denavit-Saubie, M. (1996) “Electroresponsive properties and membrane potential trajectories of three types of inspiratory neurons in the newborn mouse brain stem in vitro.” J Neurophysiol 75, Ryland W. Pace, Devin D. Mackay, Jack L. Feldman, and Christopher A. Del Negro (2007). “Cellular And Synaptic Mechanisms That Generate Inspiratory Drive Potentials In Pre-Bötzinger Neurons In Vitro.” J. Physiology 582: Del Negro, C. A., C. Morgado-Valle, et al. (2005). "Sodium and Calcium Current-Mediated Pacemaker Neurons and Respiratory Rhythm Generation." J. Neurosci. 25(2): Del Negro, C. A., N. Koshiya, et al. (2002). "Persistent sodium current, membrane properties and bursting behavior of pre-botzinger complex inspiratory neurons in vitro." J Neurophysiol 88(5):