Characterization of somatosensory evoked potentials through fine intrafascicular stimulation via flexible carbon nanotube yarn electrodes under different isoflurane anaesthetics

Abstract

Background

While most current studies have focused on the effects of transcutaneous and extrafascicular stimulation on SEPs, intrafascicular stimulation offers a more advantageous alternative. By providing closer access to target afferent fibers, it allows for lower stimulation currents and greater nerve fiber selectivity, making it a promising approach for achieving fine tactile feedback.

New method

This study employed intrafascicular stimulation with carbon nanotube yarn (CNTy) electrodes to explore its impact on tactile feedback under different levels of isoflurane anaesthesia in rats. Bipolar and monopolar stimulation were applied to stimulate tibial nerves and the SEPs were recorded to analyse quantitatively. Results: The stimulation current threshold increased with increasing anaesthetic concentration for both bipolar and monopolar stimulation for each rat. As the anaesthesia concentration increased, the amplitude progressively decreased (P < 0.001, 1.0 % vs 2.0 %, monopolar; P < 0.01, 1.0 % vs 2.0 %, bipolar), the latency was prolonged (P < 0.01, 1.0 % vs 2.0 %, monopolar; P < 0.05, 1.0 % vs 2.0 %, bipolar), and the spectral power of early and late components significantly decreased (P < 0.01, 1.0 % vs 2.0 %, monopolar, P_early; P < 0.05, 1.0 % vs 2.0 %, monopolar, P_late). Comparison with existing methods: For the first time, this study utilized CNTy electrodes via intrafascicular stimulation to investigate the characteristics of SEPs under varying isoflurane concentrations. Conclusions: This study provides a solid foundation for quantifying tactile feedback of intrafascicular stimulation during rat experiments, and reveals among the three anesthetic concentrations tested, 1.0 % exerted the minimal impact on all measured SEP characteristics in rats.