Chronaxie calculated from current–duration and voltage–duration data


Holsheimer, Jan and Dijkstra, Emiel A. and Demeulemeester, Hilde and Nuttin, Bart (2000) Chronaxie calculated from current–duration and voltage–duration data. Journal of Neuroscience Methods, 97 (1). pp. 45-50. ISSN 0165-0270

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Abstract:To determine the rheobase and the chronaxie of excitable cells from strength–duration curves both constant-current pulses and constant-voltage pulses are applied. Since the complex impedance of the electrode-tissue interface varies with both the pulsewidth and the stimulation voltage, chronaxie values estimated from voltage–duration measurements will differ from the proper values as determined from current–duration measurements. To allow a comparison of chronaxie values obtained by the two stimulation methods, voltage–duration curves were measured in human subjects with a deep brain stimulation electrode implanted, while the current and the load impedance of the stimulation circuit were determined in vitro as a function of both stimulation voltage and pulsewidth. Chronaxie values calculated from voltage–duration data were shown to be 30–40% below those estimated from current–duration data. It was also shown that in the normal range of stimulation amplitudes (up to 7 V) the load impedance increases almost linearly with the pulsewidth. This result led us to present a simple method to convert voltage–duration data into current–duration data, thereby reducing the error in the calculated chronaxie values to ≈6%. For this purpose voltage–duration data have to be measured for pulses up to 10–20 times the expected chronaxie.
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Copyright:© 2000 Elsevier
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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