A generative model of the crab cardiac neuromuscular system with modulation
© Stern et al; licensee BioMed Central Ltd. 2011
Published: 18 July 2011
The neurogenic crab heart is driven by the cardiac ganglion (CG), a central pattern generator that is embedded within the heart itself. The CG and the heart muscle form a complete closed-loop neuromuscular system. The bursting spike pattern generated by the CG drives the contractions of the muscle. These contractions, as well as previous spiking, then modify future spike generation. The system is extensively regulated by numerous neuromodulators. Here, we present a model of the complete system, with and without modulation.
We have modeled the system, at the level of spikes and contractions, as three processes: (1) the production of the contractions by the CG spikes, (2) the dependence of the CG spikes on the contractions, and (3) the dependence of the CG spikes on their own history. Using a system-identification method that we have developed , we first characterized each process separately from experimental data collected in the blue crab, Callinectes sapidus. Process (1) was characterized from spike-elicited contraction data in terms of three functions: K, the single-spike contraction kernel, H, a history kernel, and F, a static nonlinear function. These three functions successfully predict the contraction response to arbitrary spike trains. Using a modified version of the same method, we then characterized processes (2) and (3) together from data in which the CG spike pattern was recorded in response to stretches of the muscle. This gave three additional functions: K’, a kernel describing the effect of muscle length change on the generation of CG spikes, H’, a kernel describing the effect of a CG spike on the generation of future CG spikes, and F’, another static nonlinear function. Finally, we repeated all of these steps using data collected in the presence of modulators to find, in each case, six modified kernel functions.
Supported by NS058017, NS41497, GM08224.
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