Hardware-in-the-loop simulation and analysis of magnetic recording of nerve activity

The focus of the reported research was on examination of properties of a special toroidal arrangement for magnetic recording of nerve activity. Toroidal high permeability coil placed around a nerve trunk can be used to record voltage induced by magnetic field generated by ionic nerve currents associated with propagating action potentials. The properties were examined in hardware-in-the-loop simulations that were used to identify the input-output relationship of the recording arrangement in case of different simulated intra-axonal current amplitudes and conduction velocities. Based on the recorded data, a nonlinear dynamical model (Wiener model) of the recording arrangement was identified, and subsequently used for predicting the voltage waveform expected in actual magnetic recording. This waveform was also used to estimate the potential of the method with the respect to obtainable signal quality (signal-to-noise (S/N) ratios). The manuscript also contains new theoretical results for sensitivity of toroidal and electroneurographic recording arrangements to different disturbances like, for example, EMG pickup. It can be concluded that high S/N ratios, short length, and superior disturbance rejection of the toroidal magnetic recording arrangement can make magnetic recording an attractive alternative to acute and chronic electroneurographic recording techniques.