Coding Strategies in Unmyelinated Axons: Lessons from the Grashopper Auditory System

It is usually assumed that high temporal precision of neural responses increases their ability to transmit more information. All the more surprising in the grasshopper auditory system a high temporal precision at the level of receptor neurons is drastically reduced in ascending neurons only two synapses downstream, thus suggesting the transition from a temporal code to a rate code. A possible explanation for this shift in coding strategy considers the fact that auditory signals – once locally processed – have to spread a considerable distance along unmyelinated axons before they reach the brain, where decisions are made. We suggest that in these unmyelinated axons stochastic changes in action potential transmission speed can introduce spike-timing jitter, which accumulates over distance and hence favors rate coding [1]. Our hypothesis – which we propose to test in this project – provides an attractive explanation for the observed change in coding strategy and may support a more general computational principle for signal encoding in unmyelinated axons beyond the grasshopper auditory system (see A7).
It is usually assumed that high temporal precision of neural responses increases their ability to transmit more information. All the more surprising in the grasshopper auditory system a high temporal precision at the level of receptor neurons is drastically reduced in ascending neurons only two synapses downstream, thus suggesting the transition from a temporal code to a rate code. A possible explanation for this shift in coding strategy considers the fact that auditory signals – once locally processed – have to spread a considerable distance along unmyelinated axons before they reach the brain, where decisions are made. We suggest that in these unmyelinated axons stochastic changes in action potential transmission speed can introduce spike-timing jitter, which accumulates over distance and hence favors rate coding [1]. Our hypothesis – which we propose to test in this project – provides an attractive explanation for the observed change in coding strategy and may support a more general computational principle for signal encoding in unmyelinated axons beyond the grasshopper auditory system (see A7).