Electrical stimulation is an artificial way to initiate action potentials in excitable neural tissues. We conducted pure physical reasoning of electrical stimulation influence on transmembrane ion distribution and found that neuron excitability can be affected to either increase (stronger force) or decrease (fatigue). Although it has been widely observed that electrical stimulation results in muscle fatigue, there is no previous report on increased force-generating capability of muscle during electrical stimulation. We designed enveloped high frequency stimulation (EHFS), which was applied on muscle tissue in an acute rat model. We discovered that EHFS dynamically shifts neuron excitability, which manifests itself as either increase or decrease of muscle force-generating capability. To find out why such dynamic neuron excitability shift could be observed with EHFS, we modeled using the static distributed-parameter circuit model as proposed in our previous work, and then confirmed by in vivo measurements. It turns out that EHFS achieves synchronized recruitment of motoneurons at the two stimulation electrodes connected to the positive and negative terminal of a stimulator. Then, with the considerations of neuron excitability shift, a dynamic model is built to study the generation and propagation of action potentials in external electrical stimulation, which explains the widely-observed phenomena of collision blocking in peripheral nerve stimulation. Thus, our observations on neuron excitability shift offer a glimpse into how external electrical stimulation dynamically interact with neural tissues, and guide novel electrical stimulation strategies to activate (or block) neural signals.
|Original language||English (US)|
|State||Published - Dec 3 2018|
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