Cause of Subharmonics in Local Field Potentials Recorded by Sensing-Enabled Neurostimulator

Sensing-enabled neurostimulators have become an essential technology for recording local field potentials (LFPs) during neurostimulation. However, subharmonics from indeterminate sources make interpreting LFP recordings a challenge. In this study, we investigated the characteristics and the cause of the subharmonics recorded by sensing-enabled neurostimulators. We found that the amplitudes and frequencies of the subharmonics in clinical LFPs varied with stimulation parameters. Using simulated solutions, we demonstrated that these subharmonics were device-generated noise. The cause of the subharmonics was the ripples in the stimulation pulses residual in the final LFP recordings. Our results provided a method to discriminate the subharmonic artifacts and suggested that interpretation of the subharmonics at a fractional frequency of stimulations in LFP recordings should be performed carefully.