Cantrell Donald R, Troy John B
Northwestern University Interdepartmental Neuroscience Program, Northwestern University, Evanston, IL 60208 USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:642-5. doi: 10.1109/IEMBS.2009.5333464.
Neural prostheses rely upon electric stimulation to control neural activity. However, electrode corrosion and tissue damage may result from the injection of high charge densities. During electrical stimulation with traditional voltage-controlled square-wave pulses, the current density distribution on the surface of the stimulating electrode is highly nonuniform, with the highest current densities located at the edge of disk-shaped electrodes. Current density is implicated in tissue damage and electrode corrosion because it determines the charge density distribution. Through recent computer modeling work, we have found that Gaussian and sinusoidal stimulus waveforms produce a current density distribution that is significantly more uniform than the one produced by square-wave pulses. In this manner, these non-rectangular waveforms reduce the peak current densities without decreasing the efficacy of the neural stimulus. In the present work, we utilize an in vitro mouse retinal preparation to compare the same set of alternative stimulus waveforms. The -1V amplitude voltage-controlled stimuli were delivered through 20 microm diameter titanium nitride electrodes. Importantly, when normalized for the amount of injected charge, the data demonstrate that each waveform is similarly effective at eliciting a neural response. Also, the suprathreshold Gaussian and sinusoidal waveforms possessed much lower peaks in current. For this reason, these non-rectangular waveforms may be useful in reducing electrode corrosion and tissue damage.
神经假体依靠电刺激来控制神经活动。然而，高电荷密度的注入可能导致电极腐蚀和组织损伤。在用传统的电压控制方波脉冲进行电刺激期间，刺激电极表面的电流密度分布极不均匀，最高电流密度位于圆盘形电极的边缘。电流密度与组织损伤和电极腐蚀有关，因为它决定了电荷密度分布。通过最近的计算机建模工作，我们发现高斯和正弦刺激波形产生的电流密度分布比方波脉冲产生的电流密度分布明显更均匀。通过这种方式，这些非矩形波形在不降低神经刺激效果的情况下降低了峰值电流密度。在本研究中，我们利用体外小鼠视网膜制剂来比较同一组替代刺激波形。-1V幅度的电压控制刺激通过直径为20微米的氮化钛电极施加。重要的是，当对注入电荷量进行归一化时，数据表明每个波形在引发神经反应方面同样有效。此外，阈上高斯和正弦波形的电流峰值要低得多。因此，这些非矩形波形可能有助于减少电极腐蚀和组织损伤。
