Abstract
The vagus nerve is the largest autonomic nerve and a major target of stimulation therapies for a wide variety of chronic diseases. However, chronic recording from the vagus nerve has been limited, leading to significant gaps in our understanding of vagus nerve function and therapeutic mechanisms. In this study, we use a carbon nanotube yarn (CNTY) biosensor to chronically record from the vagus nerves of freely moving rats for over 40 continuous hours. Vagal activity was analyzed using a variety of techniques, such as spike sorting, spike-firing rates, and interspike intervals. Many spike-cluster-firing rates were found to correlate with food intake, and the neural-firing rates were used to classify eating and other behaviors. To our knowledge, this is the first chronic recording and decoding of activity in the vagus nerve of freely moving animals enabled by the axon-like properties of the CNTY biosensor in both size and flexibility and provides an important step forward in our ability to understand spontaneous vagus-nerve function.
Highlights
The vagus nerve innervates nearly every internal organ, providing sensory input to the brain and parasympathetic-control inputs to the viscera
Vagus-nerve stimulation has been used to treat a wide variety of diseases [6], most successfully implemented for the treatment of epilepsy [7], even while the mechanisms are not well understood and direct recordings of vagal activity associated with disease are not available [8]
We have previously shown that carbon nanotube yarn (CNTY) electrodes can record spikes from the glossopharyngeal and vagus nerves in anesthetized rats and can be used to measure vagal tone in freely moving animals [26,27]
Summary
The vagus nerve innervates nearly every internal organ, providing sensory input to the brain and parasympathetic-control inputs to the viscera. We have previously shown that carbon nanotube yarn (CNTY) electrodes have favorable properties for nerve interfacing: their small size, high flexibility, and low impedance They provide a stable, high-SNR interface for chronic recording in small autonomic nerves in rats, with high-quality signals continuing up to four months after implantation [26]. We have developed techniques for recording activity in the cervical vagus nerves of rats without anesthesia, allowing for the first chronic recordings of truly spontaneous vagal activity This technology has been successfully applied to make the first direct measurements of vagal tone in freely moving animals [27]. There are reflex pathways which modulate efferent vagal activity in response to gastric distention and contractions [32] Such signals have not been reported from chronic, unanesthetized animals, and this CNTY-electrode biosensor demonstrates the ability to decode vagal activity related to various animal behaviors, such as eating. We report several spike clusters that show tuning to animal eating, and the firing dynamics of multiple decoded spike clusters can be used to classify eating compared to drinking, grooming, and resting behaviors
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