In vivo peripheral nerve activation using sinusoidal low-frequency alternating currents

Area of Science:

• Neuroscience
• Biomedical Engineering
• Physiology

Background:

• Low-frequency alternating current (LFAC) is a novel waveform explored for nerve conduction block.
• Previous research suggested a potential frequency dependency for nerve activation thresholds.
• The Hering-Breuer (HB) reflex was utilized as a biomarker for cervical vagus nerve activation.

Purpose of the Study:

• To investigate if increasing LFAC amplitude activates nerve fibers in autonomic nerves.
• To determine the frequency-dependent activation thresholds of autonomic nerve fibers using LFAC.
• To assess the potential of LFAC as a neurostimulation modality.

Main Methods:

• Experiments were conducted on isoflurane-anesthetized swine.
• Bipolar stimulating and tripolar recording cuff electrodes were implanted on the vagus nerve.
• Standard pulse stimulation and continuous sinusoidal LFAC (5-20 Hz) were applied to elicit and detect nerve activation via the HB reflex.

Main Results:

• LFAC was capable of eliciting an HB response, indicating autonomic nerve fiber activation.
• LFAC activation thresholds were frequency-dependent, with lower thresholds at higher frequencies (e.g., 0.44 mA at 20 Hz).
• LFAC stimulation correlated with the activation of slower nerve fiber components associated with the HB reflex, without observed nerve or electrode damage.

Conclusions:

• The study demonstrates the feasibility of using LFAC waveforms at 5, 10, and 20 Hz to activate autonomic nerve fibers.
• LFAC presents a potential new modality for neurorehabilitation.
• The findings support further investigation into LFAC for therapeutic applications.