Stabilization of cutaneous sensation elicited by electric stimulation and its application to sensory feedback

以神经系统完整的受试者为研究对象，研究皮肤阻抗的绝对阈值与等效电路参数之间的关系。等效电路由并联的电阻Rp和电容Cp加上串联的电阻Rs组成。结果发现，对于带有导电浆料的Ag-AgCl电极，Rp和Cp的频率特性随时间的变化与反复剥皮引起的变化相似。10Hz时Cp和Rp值与绝对阈值有较高的相关系数。接下来，我们利用固体凝胶电极测量刺激脉冲电流和方波脉冲的村庄波，估计等效电路的参数。绝对阈值在反复电刺激皮肤时升高，在没有电刺激的情况下充分休息后降低。Rp随反复电刺激而降低，休息后升高，而Cp无变化。Rp与绝对阈值之间存在显著相关性。结果表明，电刺激角质层对绝对阈值和皮肤阻抗均有影响；他们还指出，实时评估对于稳定电刺激引起的皮肤感觉很重要。Rp降低的可能原因是由于电荷转移导致导电浆料渗透到角质层，从而增加了离子电导率。阈值幅度的增加被认为是由于角质层中离子或电导率的增加而导致电流垫变宽的结果。因此，有必要对阈值与阻抗参数之间的关系机理进行研究。

The relationship between absolute threshold and the parameters of an electrical equivalent circuit for skin impedance was examined with neurologically intact subjects. The equivalent circuit consisted of resistance Rp and capacitance Cp connected in parallel, plus resistance Rs in series to both.As a result, for Ag-AgCl electrodes with electroconductive paste, variationsover time of the frequency characteristics of Rp and Cp were found to be similar to the changes caused by repeatedly stripping the skin. Values of Cp and Rp at 10Hz were found to relate to the absolute threshold with high correlation coefficients. Next we estimated the parameters of the equivalent circuit by measuring stimulus pulse current abd viltage waves of square-wave pulses using solid-gel electrodes. The absolute threshold increased with repeated electrical stimulation to the skin and decreased after adequate rest with no electrical stimulation. Rp decreased with repeated electrical stimulation and increased after rest, while Cp did not change. A significant correlation between Rp 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 cutaneuos sensation elicited by electrical stimulation.Possible reasons for decreasing Rp were an increase of ionic conductivity due to osmosis of electroconductive paste into the stratum corneum due to charge transfer. The increase of the threshold amplitude was considered to be the result of broadened current pad due to increases if ionic or electric conductivities in the stratum corneum. It is necessary to clarify the mechanism of those relationsship between threshold and impedance parameters.