Donaldson N, Rieger R, Schuettler M, Taylor J
Implanted Devices Group, University College London, London, UK.
Med Biol Eng Comput. 2008 Oct;46(10):1005-18. doi: 10.1007/s11517-008-0365-4. Epub 2008 Aug 12.
Using a multi-electrode nerve-signal recording cuff and a method of signal processing described previously, activity in axons with different propagation velocities can be distinguished, and the relative amplitude of the small-fibre signals increased. This paper is, largely, an analysis of the selectivity and noise of this system though impedance measurements from an actual cuff are included. The signal processor includes narrow band-pass filters. It is shown that the selectivity and noise both increase with the centre frequencies of these filters. A convenient approach is to make the filter frequencies inversely related to the artificial time delays so that the filter 'Q's are approximately constant and the noise densities are equal for all velocity filters. Numerical calculations, using formulae for this system and for the conventional tripole, based on a fixed cuff size and tissue resistivity, find the number of action potentials per second that must pass through the cuff so that the signal power equals the noise power. For slow fibres (20 m/s), the rate is 14 times lower for the multi-electrode cuff than the tripole, a significant advantage for recording from these fibres.
使用多电极神经信号记录袖带以及之前描述的信号处理方法，可以区分不同传播速度轴突的活动，并且小纤维信号的相对幅度会增加。尽管包含了来自实际袖带的阻抗测量，但本文主要是对该系统的选择性和噪声进行分析。信号处理器包括窄带通滤波器。结果表明，选择性和噪声都随着这些滤波器的中心频率而增加。一种简便的方法是使滤波器频率与人为时间延迟成反比，这样滤波器的“品质因数”大致恒定，并且所有速度滤波器的噪声密度相等。基于固定的袖带尺寸和组织电阻率，使用该系统和传统三极子的公式进行数值计算，得出每秒必须通过袖带的动作电位数量，以使信号功率等于噪声功率。对于慢纤维（20米/秒），多电极袖带的速率比三极子低14倍，这对于从这些纤维进行记录来说是一个显著优势。
