Efficient Coding in the Olfactory Receptor Neuron Signaling Pathway

Abstract

The efficiency of neuronal coding has been studied extensively within the context of spike trains. Significantly less attention has been paid towards coding efficiency in biological signaling pathways. This study applies Shannon information theory to the olfactory receptor neuron signaling pathway to determine under what conditions the olfactory system can code most efficiently. We explore which types of odor stimuli the vertebrate olfactory system is most proficient at encoding by analyzing simulated data from a computational model of the pathway. We focus on odor stimuli of constant length but of varying concentration. This study concludes that the olfactory system's ability to encode such stimuli decreases significantly when presented with odor pulses of length greater than one second. We further explore the roles of particular signaling molecules in contributing to this decrease in coding efficiently. Finally, we perform a parameter sensitivity analysis on our information-theoretical calculations to identify the mechanisms responsible for information bottlenecks. We found that variations in upstream mechanism rate coefficients such as the G-protein activation rate have a significant effect on the transmission of information over stimuli longer than one second. In addition, parameter variations of the calcium extrusion rate through the sodium-calcium exchanger had a significant effect on information transfer over all pulse lengths.