McConnell G C, Butera R J, Bellamkonda R V
Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, 30332, USA.
J Neural Eng. 2009 Oct;6(5):055005. doi: 10.1088/1741-2560/6/5/055005. Epub 2009 Sep 1.
The widespread adoption of neural prosthetic devices is currently hindered by our inability to reliably record neural signals from chronically implanted electrodes. The extent to which the local tissue response to implanted electrodes influences recording failure is not well understood. To investigate this phenomenon, impedance spectroscopy has shown promise for use as a non-invasive tool to estimate the local tissue response to microelectrodes. Here, we model impedance spectra from chronically implanted rats using the well-established Cole model, and perform a correlation analysis of modeled parameters with histological markers of astroglial scar, including glial fibrillary acid protein (GFAP) and 4',6-diamidino-2- phenylindole (DAPI). Correlations between modeled parameters and GFAP were significant for three parameters studied: Py value, R(o) and |Z|(1 kHz), and in all cases were confined to the first 100 microm from the interface. Py value was the only parameter also correlated with DAPI in the first 100 microm. Our experimental results, along with computer simulations, suggest that astrocytes are a predominant cellular player affecting electrical impedance spectra. The results also suggest that the largest contribution from reactive astrocytes on impedance spectra occurs in the first 100 microm from the interface, where electrodes are most likely to record electrical signals. These results form the basis for future approaches where impedance spectroscopy can be used to evaluate neural implants, evaluate strategies to minimize scar and potentially develop closed-loop prosthetic devices.
目前，神经假体装置的广泛应用受到我们无法可靠记录长期植入电极的神经信号的阻碍。局部组织对植入电极的反应在多大程度上影响记录失败尚不清楚。为了研究这一现象，阻抗谱已显示出有望作为一种非侵入性工具来估计局部组织对微电极的反应。在这里，我们使用成熟的科尔模型对长期植入大鼠的阻抗谱进行建模，并对建模参数与星形胶质瘢痕的组织学标记物进行相关性分析，包括胶质纤维酸性蛋白（GFAP）和4',6-二脒基-2-苯基吲哚（DAPI）。对于所研究的三个参数：Py值、R(o)和|Z|(1 kHz)，建模参数与GFAP之间的相关性显著，并且在所有情况下都局限于距界面的前100微米内。Py值是在前100微米内也与DAPI相关的唯一参数。我们的实验结果以及计算机模拟表明，星形胶质细胞是影响电阻抗谱的主要细胞成分。结果还表明，反应性星形胶质细胞对阻抗谱的最大贡献发生在距界面的前100微米内，电极最有可能在此处记录电信号。这些结果为未来的方法奠定了基础，在这些方法中，阻抗谱可用于评估神经植入物、评估最小化瘢痕的策略并潜在地开发闭环假体装置。
