title: Direct current contamination of kilohertz frequency alternating current waveforms.
abstract: Kilohertz frequency alternating current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms.
authors.affiliation: Case Western Reserve University, Cleveland, OH 44106, USA. Electronic address: Manfred.Franke@gmail.com.
authors.forename: Manfred
authors.initials: M
authors.lastname: Franke
authors.affiliation: Case Western Reserve University, Cleveland, OH 44106, USA. Electronic address: nxb26@case.edu.
authors.forename: Niloy
authors.initials: N
authors.lastname: Bhadra
authors.affiliation: Case Western Reserve University, Cleveland, OH 44106, USA. Electronic address: nxb11@case.edu.
authors.forename: Narendra
authors.initials: N
authors.lastname: Bhadra
authors.affiliation: MetroHealth Medical Center, Cleveland, OH 44109, USA; Case Western Reserve University, Cleveland, OH 44106, USA; Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA. Electronic address: klk4@case.edu.
authors.forename: Kevin
authors.initials: K
authors.lastname: Kilgore
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001703:Biophysics; D025802:Electric Capacitance; D004553:Electric Conductivity; D004558:Electric Stimulation / Q000295:instrumentation / Q000379:methods; D004867:Equipment Design; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology*; D009407:Nerve Block / Q000295:instrumentation / Q000379:methods; D009431:Neural Conduction / Q000502:physiology*
keywords: DC in KHFAC; Direct current; HFAC; KHFAC; Kilohertz high frequency alternating current; Nerve block