Modeling the complete cardiac ganglion – heart muscle network of the crab Callinectes sapidus

Abstract

In the neurogenic heart of the blue crab, Callinectes sapidus [1], the cardiac ganglion (CG) and the heart muscle form a closed-loop network. Spikes generated by the CG drive contractions of the muscle, which in turn provide feedback to the CG to modify its future spiking. We have modeled the activity of the whole network at the level of the spikes and contractions. At this level, the network can be regarded as composed of three processes (arrows in Fig. 1A): (1) the production of the contractions by the CG spikes, (2) the feedback from the contractions back to the CG, and (3) the endogenous spiking of the CG itself. We first characterized each process separately from experimental data, using a decoding method that we developed for this purpose [2]. For process (1), we obtained three elementary functions to describe the transform from spikes to contractions: K, the single-spike contraction response kernel; H, a history kernel; and F, a static nonlinear function. These three functions were able to successfully predict the contraction response to arbitrary spike trains [3,4]. For processes (2) and (3), we used a modified version of the same decoding method to find three further elementary functions: H', a history kernel that describes the endogenous spike generation by the CG, that is, the probability of generating a spike given the previous history of spiking; K', a feedback kernel that describes the probability of spiking given the previous history of contraction; and F', a static nonlinear function [5]. We then combined the six elementary functions in a generative model of the complete system implemented in a simulator in MATLAB. The model generates, from the spikes and contractions up to any given time, the next spike and confrom Eighteenth Annual Computational Neuroscience Meeting: CNS*2009 Berlin, Germany. 18–23 July 2009