電流刺激による皮膚受容感覚の安定化のための絶対閾値と皮膚インピーダンスの関連性の検討(1部生体計測)

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This study focused on stabilizing the sensationselicited by electrical stimulation applied to the skin through surface electrodes, a technique widely used in sensory feedback research. The relationship between absolute threshold (the minimum stimulus amplitude that causes sensation) and the parameters of an electrical equivalent circuit for skin impedance was examined with neurologically intact subjects. Electric current pulse stimulation at 100 Hz frequency and pulse widths between 0.08 and 0.5ms was used to elicit a cutaneous sensation. The electrical equivalent circuit for skin impedance consisted of resistance R_p and capacitance C_p connected in parallel, plus resistance R_s connected in series to both. First, we estimated the parameters of the equivalent circuit by the skin impedance measured with sinusoidal signals (R_<ps> and C_<ps>), and we examined their relevance to the absolute threshold. For Ag-AgCl electrodes used with electroconductive paste, variations over time of the frequency characteristics of R_<ps> and C_<ps> were found to be similar to the changes caused by repeatedly stripping the skin. Values of C_<ps> and R_<ps> at 10Hz were found to relate to the absolute threshold with high correlation coefficients. For a solid-gel Ag-AgCl electrode, changes of absolute threshold, R_<ps> and C_<ps> caused by increasing size of the solid-gel electrode were similar to variations over time obtained using electrodes with electroconductive paste. Correlations between the threshold and values of R_<ps> and C_<ps> at 10 Hz were also observed. Next, we estimated the parameters of the equivalent circuit by measuring stimulus pulse current and voltage waves of square-wave stimulus pulses using solid-gel electrodes (R_<ps> and C_<pr>). We then examined their relevance to the absolute threshold. The absolute threshold increased with repeated electrical stimulation to the skin and decreased after adequate rest with no electrical stimulation. The value of R_<pr> decreased with repeated electrical stimulation and increased after rest, while the value of C_<pr> did not change. These variations became minor after preparation of the skin for removing the stratum corneum. A significant correlation between R_<pr> and the absolute threshold was observed. These results show that electrical stimulation to the stratum corneum affects both absolute threshold and skin impedance; they also indicate that real-time evaluation is important for stabilizing cutaneous sensation elicited by electrical stimulation. The relevance of R_p to the threshold was shown in both methods that were used to estimate the parameters. Possible reasons for decreasing R_p were an increase of ionic conductivity due to osmosis of electroconductive paste into the stratum corneum or an increase of electric charge in the stratum corneum due to charge transfer by electrical stimulation through the skin. The increase of the threshold amplitude was considered to be the result of broadened current path due to increases of ionic or electric conductivities in the stratum corneum. It is necessary to clarify the mechanism of the relationship between the threshold and impedance parameters in order to develop a technique for stabilizing electrocutaneous sensation.
バイオメカニズム学会の論文
2002-06-25

電流刺激による皮膚受容感覚の安定化のための絶対閾値と皮膚インピーダンスの関連性の検討(1部生体計測)

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電流刺激による皮膚受容感覚の安定化のための絶対閾値と皮膚インピーダンスの関連性の検討(1部 生体計測)

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電流刺激による皮膚受容感覚の安定化のための絶対閾値と皮膚インピーダンスの関連性の検討(1部生体計測)