Department of Otolaryngology Head and Neck Surgery, Johns Hopkins University, Baltimore, MD 21208, USA.
IEEE Trans Neural Syst Rehabil Eng. 2013 Mar;21(2):319-28. doi: 10.1109/TNSRE.2013.2245423.
While effective in treating some neurological disorders, neuroelectric prostheses are fundamentally limited because they must employ charge-balanced stimuli to avoid evolution of irreversible electrochemical reactions and their byproducts at the interface between metal electrodes and body fluids. Charge-balancing is typically achieved by using brief biphasic alternating current (AC) pulses, which typically excite nearby neural tissues but cannot efficiently inhibit them. In contrast, direct current (DC) applied via a metal electrode in contact with body fluids can excite, inhibit and modulate sensitivity of neurons; however, chronic DC stimulation is incompatible with biology because it violates charge injection limits that have long been considered unavoidable. In this paper, we describe the design and fabrication of a Safe DC Stimulator (SDCS) that overcomes this constraint. The SCDS drives DC ionic current into target tissue via salt-bridge micropipette electrodes by switching valves in phase with AC square waves applied to metal electrodes contained within the device. This approach achieves DC ionic flow through tissue while still adhering to charge-balancing constraints at each electrode-saline interface. We show the SDCS's ability to both inhibit and excite neural activity to achieve improved dynamic range during prosthetic stimulation of the vestibular part of the inner ear in chinchillas.
虽然神经电假体在治疗某些神经紊乱方面非常有效，但它们从根本上受到限制，因为它们必须采用电荷平衡刺激，以避免金属电极和体液界面处不可逆的电化学反应及其副产物的发展。电荷平衡通常通过使用短暂的双相交流电 (AC) 脉冲来实现，这种脉冲通常可以激发附近的神经组织，但不能有效地抑制它们。相比之下，通过与体液接触的金属电极施加的直流电可以激发、抑制和调节神经元的敏感性；然而，慢性直流刺激与生物学不兼容，因为它违反了长期以来被认为不可避免的电荷注入限制。在本文中，我们描述了一种安全直流刺激器 (SDCS) 的设计和制造，该刺激器克服了这一限制。SCDS 通过在与施加到设备内金属电极的交流方波同步切换的阀来通过盐桥微电极将直流离子电流驱动到目标组织中。这种方法在每个电极-盐溶液界面处仍遵循电荷平衡约束的情况下，实现了组织内的直流离子流动。我们展示了 SDCS 抑制和激发神经活动的能力，以在对南美栗鼠内耳前庭部分进行假体刺激时提高动态范围。
