Resurgent Na+ Current Offers Noise Modulation in Bursting Neurons.

Neurons utilize bursts of action potentials as an efficient and reliable way to encode information. It is likely that the intrinsic membrane properties of neurons involved in burst generation may also participate in preserving its temporal features. Here we examined the contribution of the persistent and resurgent components of voltage-gated Na+ currents in modulating the burst discharge in sensory neurons. Using mathematical modeling, theory and dynamic-clamp electrophysiology, we show that, distinct from the persistent Na+ component which is important for membrane resonance and burst generation, the resurgent Na+ can help stabilize burst timing features including the duration and intervals. Moreover, such a physiological role for the resurgent Na+ offered noise tolerance and preserved the regularity of burst patterns. Model analysis further predicted a negative feedback loop between the persistent and resurgent gating variables which mediate such gain in burst stability. These results highlight a novel role for the voltage-gated resurgent Na+ component in moderating the entropy of burst-encoded neural information.

A computational model for motor pattern switching between taste-induced ingestion and rejection oromotor behaviors.

The mechanism of switching activity patterns in a central pattern generator is fundamental to the generation of diverse motor behaviors. Based on what is known about a brainstem substrate mediating the oral components of ingestion and rejection, we use computational techniques to construct a hypothetical multifunctional network that switches between the motor outputs of ingestion (licking) and rejection (gaping). The network was constructed using single-compartment conductance-based models for individual neurons based on Hodgkin-Huxley formalism. Using a fast-slow reduction and geometric analysis we describe a mechanism for pattern switching between licks and gapes. The model supports the hypothesis that a single configuration of network connections can produce both activity patterns. It further predicts that prolonged inhibition of some network neurons could lead to a switch in network activity from licks to gapes.