Department of Neurosurgery, Epilepsy Center, Translational Neurotechnology Lab, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, AG Ball, Engelbergerstr. 21 3.0 EG, 79106 Freiburg, Germany. Department of Neurosurgery, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Str. 64, 79106 Freiburg, Germany. Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 102, 79110 Freiburg, Germany. BrainLinks-BrainTools Cluster of Excellence, University of Freiburg, Georges-Koehler-Allee 80, 79110 Freiburg, Germany.
J Neural Eng. 2017 Oct;14(5):056004. doi: 10.1088/1741-2552/aa785e. Epub 2017 Jun 9.
OBJECTIVE: Innovations in micro-electrocorticography (µECoG) electrode array manufacturing now allow for intricate designs with smaller contact diameters and/or pitch (i.e. inter-contact distance) down to the sub-mm range. The aims of the present study were: (i) to investigate whether frequency ranges up to 400 Hz can be reproducibly observed in µECoG recordings and (ii) to examine how differences in topographical substructure between these frequency bands and electrode array geometries can be quantified. We also investigated, for the first time, the influence of blood vessels on signal properties and assessed the influence of cortical vasculature on topographic mapping. APPROACH: The present study employed two µECoG electrode arrays with different contact diameters and inter-contact distances, which were used to characterize neural activity from the somatosensory cortex of minipigs in a broad frequency range up to 400 Hz. The analysed neural data were recorded in acute experiments under anaesthesia during peripheral electrical stimulation. MAIN RESULTS: We observed that µECoG recordings reliably revealed multi-focal cortical somatosensory response patterns, in which response peaks were often less than 1 cm apart and would thus not have been resolvable with conventional ECoG. The response patterns differed by stimulation site and intensity, they were distinct for different frequency bands, and the results of functional mapping proved independent of cortical vascular. Our analysis of different frequency bands exhibited differences in the number of activation peaks in topographical substructures. Notably, signal strength and signal-to-noise ratios differed between the two electrode arrays, possibly due to their different sensitivity for variations in spatial patterns and signal strengths. SIGNIFICANCE: Our findings that the geometry of µECoG electrode arrays can strongly influence their recording performance can help to make informed decisions that maybe important in number of clinical contexts, including high-resolution brain mapping, advanced epilepsy diagnostics or brain-machine interfacing.
目的：微电极皮层电图（µECoG）电极阵列制造的创新现在允许设计出具有更小接触直径和/或间距（即接触间距离）的精细设计，达到亚毫米范围。本研究的目的是：（i）研究在 µECoG 记录中是否可以重复观察到高达 400 Hz 的频率范围，以及（ii）检查这些频带和电极阵列几何形状之间的拓扑亚结构差异如何被量化。我们还首次研究了血管对信号特性的影响，并评估了皮质血管对地形映射的影响。
方法：本研究使用了两种具有不同接触直径和接触间距离的 µECoG 电极阵列，这些阵列用于在高达 400 Hz 的宽频率范围内表征来自小型猪感觉皮层的神经活动。分析的神经数据是在麻醉下的急性实验中记录的，在实验过程中进行外周电刺激。
主要结果：我们观察到 µECoG 记录可靠地揭示了多焦点皮质感觉响应模式，其中响应峰值通常相距不到 1 厘米，因此用传统的 ECoG 无法分辨。响应模式因刺激部位和强度而异，在不同的频带中不同，功能映射的结果证明与皮质血管无关。我们对不同频带的分析显示，拓扑亚结构中的激活峰数量存在差异。值得注意的是，两个电极阵列之间的信号强度和信噪比存在差异，这可能是由于它们对空间模式和信号强度变化的敏感性不同所致。
意义：我们发现 µECoG 电极阵列的几何形状可以强烈影响其记录性能，这有助于在许多临床情况下做出明智的决策，包括高分辨率脑映射、高级癫痫诊断或脑机接口。
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