In a recent letter to the editor, Langenbach and colleagues [1] cited concerns about the repeated use of Ag/AgCl electrodes in 4x1 High Definition transcranial direct current stimulation (HDtDCS). Briefly, the authors reported increased impedance (with sudden, occasional cessation of stimulation) and visual evidence of oxidation (blackening of the electrode surface) after about 8 sessions inwhich the same electrodewas used as the anode (2mA) and four other “ring” electrodes served as cathodes for up to 20minutes per session. Relevant additional methodological information obtained via personal communication with Dr. Langenbach (April 3, 2020) includes the following: 1) stimulation used a neuroConn DC-Stimulator MC (software version 1.6.0), which allows for independent electrical current modulation of each electrode, 2) investigators used a standard EEG cap and placed gel directly into the holes (i.e., no specialized holders were used), 3) a variable amount of gel was used (both across electrodes and participants) but impedance was always <8kU, 4) total duration of use varied for each set of electrodes. Langenbach and colleagues discussed methods to reduce wear including electrode rotation as well as the need for increased transparency in reporting about electrode use/care. Given the above noted concerns, we felt it important to share our experiences with HD-tDCS (or multi-electrode tDCS) using data from our ongoing randomized trial as an example (NCT02155946 (see also ref 3)). In this study, participants with mild cognitive impairment (MCI) receive 5 consecutive daily sessions of active (2mA for 20 minutes/session) or sham HD-tDCS. As previously noted [3], the center anode is positioned at F5, while the ring cathodes are positioned at Fp1, F1, C5, and F9. Upon starting this line of research, our initial review of the literature [2] and recommendations from representatives at Soterix Medical Inc. (from whom units were acquired) indicated that electrodes are reusable for about 10 sessions at an intensity of 2mA if proper electrode rotation is maintained, such that no one electrode acts as the “center” for more than two sessions. Such recommendations precede, but ultimately support, Langenbach et al.‘s suggestion for electrode rotation. Fig. 1 is an example of our standard rotation, where each electrode is assigned a letter and teammembers are required to position electrodes at the pre-designated locations for each session. In this study [3], each set of electrodes is used for two participants (participant 1 1⁄4 sessions 1e5; participant 2 1⁄4 sessions 6e10) so that each electrode serves as the center for only two sessions. Our trial uses a Soterix Medical Inc. 4x1 HD-tDCS unit, which provides full amplitude to the center channel/electrode but passively splits current to the ring electrodes, and is powered by a Soterix Medical Inc. Clinical Trials (CT) unit. We use electrode

中文翻译：

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可靠使用氯化银 HD-tDCS 电极

在最近给编辑的一封信中，Langenbach 及其同事 [1] 提到了对在 4x1 高清经颅直流电刺激 (HDtDCS) 中重复使用 Ag/AgCl 电极的担忧。简而言之，作者报告了大约 8 次使用相同电极作为阳极 (2mA) 和其他四个“环形”电极后，阻抗增加（突然、偶尔停止刺激）和氧化的视觉证据（电极表面变黑）每次会话最多可用作阴极 20 分钟。通过与 Langenbach 博士（2020 年 4 月 3 日）的个人交流获得的相关附加方法信息包括以下内容：1) 使用 NeuroConn DC-Stimulator MC（软件版本 1.6.0）进行刺激，允许对每个电极进行独立的电流调制, 2) 研究人员使用标准 EEG 帽并将凝胶直接放入孔中（即，未使用专门的支架），3）使用了不同数量的凝胶（跨电极和参与者），但阻抗始终 <8kU，4）每组电极的总使用时间不同。Langenbach 及其同事讨论了减少磨损的方法，包括电极旋转以及提高电极使用/护理报告透明度的需要。鉴于上述问题，我们认为使用我们正在进行的随机试验的数据作为示例（NCT02155946（另见参考文献 3））分享我们在 HD-tDCS（或多电极 tDCS）方面的经验很重要。在这项研究中，轻度认知障碍 (MCI) 的参与者每天接受 5 次连续的活动（2mA 持续 20 分钟/次）或假 HD-tDCS。如前所述[3]，中心阳极位于 F5，而环形阴极位于 Fp1、F1、C5 和 F9。在开始这一系列研究时，我们对文献 [2] 的初步审查和 Soterix Medical Inc.（从其获得单位）代表的建议表明，如果正确旋转电极，电极可以在 2mA 的强度下重复使用约 10 次保持，以便没有一个电极充当超过两个会话的“中心”。这些建议先于但最终支持 Langenbach 等人关于电极旋转的建议。图 1 是我们标准轮换的示例，其中每个电极都分配了一个字母，并且团队成员需要在每个会话的预先指定位置放置电极。在本研究中[3]，每组电极用于两个参与者（参与者 1 1⁄4 会话 1e5；参与者 2 1⁄4 会话 6e10），因此每个电极仅作为两个会话的中心。我们的试验使用 Soterix Medical Inc. 4x1 HD-tDCS 装置，它为中心通道/电极提供全振幅，但被动地将电流分流到环形电极，并由 Soterix Medical Inc. 临床试验 (CT) 装置供电。我们使用电极