A computational study to evaluate the activation pattern of nerve fibers in response to interferential currents stimulation.

Interferential current (IFC) is one of the most popular electrical currents used in electrotherapy. However, there have been limited studies investigating how this stimulation affects the nerve fibers. The aim of this computational study was to evaluate the temporal and spatial patterns of fiber activation in IFC therapy for different modulation and carrier frequencies. The interferential currents were applied by two pairs of point electrodes perpendicular to each other in an infinite homogeneous medium, and a model of myelinated nerve fibers was implemented in NEURON to study the neural response. The activation thresholds for different positions of the fiber and the resultant firing patterns were evaluated. The results suggest that the fibers may fire continuously or in bursts, with frequencies equal or higher than the modulation frequency, or may be blocked, based on their position relative to the electrodes, the modulation frequency and the stimulus strength. The results confirm traditional belief about the role of the modulation frequency in firing frequency of nerve fibers and describe a possible mechanism for less sensation of pain, due to blockage of the fibers by the high-frequency nature of the interferential currents.