High-frequency, sinusoidal bursts activate nerve fibers in the earthworm

Figure 1: High-frequency burst stimulation (left) triggers compound action potentials (CAP, right inset) in the medial giant fiber of the earthworm.Spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS) are a cornerstone of modern bioelectronic interventions aiming at providing targeted therapies for various conditions such as chronic pain, epilepsy or chronic inflammation. Standard neuromodulation approaches mostly use mono- or bi-phasic pulses with varying amplitudes and intervals to deliver electrical stimulation to peripheral nerves via mono-, bi-, or tri-polar electrodes to activate nerve fibers. At the same time, continuous, high frequency sinusoidal stimulation has been linked to blocking of nerve fibers. The application of short, high frequency pulses, however, has not been investigated yet in detail.Here we use a simple animal model for nerve activation, the common earthworm lumbricus terrestris, to demonstrate how short, sinusoidal bursts can effectively activate different nerve fibers at kilohertz frequencies. We show that sinusoidal burst stimulation with different phase allows the activation of action potentials with different effective timing. These results demonstrate that intermittent, high frequency sinusoidal stimulation can have advantageous effects that could be exploited for new stimulation strategies. We discuss possible applications of this approach in peripheral nerve stimulation and neuromodulation treatments.