期刊
JOURNAL OF NEUROSCIENCE METHODS
卷 97, 期 1, 页码 45-50出版社
ELSEVIER
DOI: 10.1016/S0165-0270(00)00163-1
关键词
current-duration measurements; voltage-duration measurements; chronaxie; rheobase; deep brain stimulation
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 approximate to 6%. For this purpose voltage-duration data have to be measured for pulses up to 10-20 times the expected chronaxie. (C) 2000 Elsevier Science B.V. All rights reserved.
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