Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA.
Department of Physical Medicine and Rehabilitation, University of Pittsburgh, Pittsburgh, PA, 15213, USA.
Sci Rep. 2018 Aug 30;8(1):13067. doi: 10.1038/s41598-018-31247-2.
The recent proliferation of high-density microelectrode arrays has inspired several new applications of electrical microstimulation, including restoration of sensory functions in the visual, auditory, and somatosensory systems. In each case, the goal is to achieve precisely targeted activation of neurons, while patterning the location and timing of stimulation across the array to mimic naturalistic patterns of neural activity. However, when two or more electrodes deliver stimulation pulses at the same time, the electric fields created by each electrode interact. The effects of field interactions on neuronal recruitment depend on several factors, which have been studied extensively at the macro-scale but have been overlooked in the case of high density arrays. Here, we report that field interactions can significantly affect neural recruitment, even with low amplitude stimulation. We created a computational model of peripheral nerve axons to estimate stimulation parameters sufficient to generate neural recruitment during synchronous and asynchronous stimulation on two microelectrodes located within the peripheral nerve. Across a range of stimulus amplitudes, the model predicted that synchronous stimulation on adjacent electrodes (400 µm separation), would recruit 2-3 times more neurons than during asynchronous stimulation. Our results suggest that field interactions should not be ignored when designing multichannel microstimulation paradigms, even at threshold-level stimulus amplitudes.
最近高密度微电极阵列的激增激发了电微刺激的几个新应用，包括恢复视觉、听觉和体感系统中的感觉功能。在每种情况下，目标都是实现对神经元的精确靶向激活，同时在阵列上对刺激的位置和时间进行图案化，以模拟自然的神经活动模式。然而，当两个或更多电极同时施加刺激脉冲时，每个电极产生的电场会相互作用。场相互作用对神经元募集的影响取决于几个因素，这些因素在宏观尺度上已经得到了广泛研究，但在高密度阵列的情况下却被忽视了。在这里，我们报告说，即使在低幅度刺激的情况下，场相互作用也会显著影响神经元募集。我们创建了一个周围神经轴突的计算模型，以估计在位于周围神经内的两个微电极上进行同步和异步刺激时产生神经募集所需的刺激参数。在一系列刺激幅度下，该模型预测相邻电极（400µm 间隔）的同步刺激将比异步刺激招募 2-3 倍以上的神经元。我们的结果表明，即使在阈值级别的刺激幅度下，在设计多通道微刺激范式时，也不应忽略场相互作用。
