Imaging of evoked neural activity in the rat brain using Electrical Impedance Tomography
Imaging of evoked neural activity in the rat brain using Electrical Impedance Tomography
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发表时间：
2019
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通讯作者：
A. M. Faulkner
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作者：
A. M. Faulkner
电阻抗断层成像（EIT）是一种技术，可以重建电导率的变化，在体积从多个传输阻抗测量。可以测量与神经元去极化相关的阻抗变化，因此已经提出使用EIT作为功能性脑成像技术。提出的工作已寻求延长EIT在大鼠模型中从一个专门的皮层成像技术，一个敏感的皮层下活动。第1章介绍了EIT的原理，并概述了以前的EIT实验。第2章和第3章重点讨论了使用皮层电极阵列时，皮层下活动成像参数的优化。在第二章中，EIT协议的生成方法，旨在提高敏感性，在大脑中的深感兴趣的区域的发展。发现使电流密度的大小最大化的方案是最佳的。进行EIT测量的最佳频率在第3章中通过表征使用高达10 kHz的载波频率进行体感刺激期间丘脑和皮层的阻抗响应来确定。在1475 Hz处观察到皮质和丘脑中的最大SNR。第四章研究了皮层电极对上行神经活动的成像能力。尽管使用了先前发现的优化参数，但来自丘脑的小幅度信号阻止了比皮层更深的成像。随后的模拟表明，使用这种类型的电极，EIT成像仅限于皮质表面以下2.6 mm。在第五章中，评估了用神经探针进行EIT测量的可行性。通过沿着皮质电极阵列实施神经探针，对体感刺激期间在正确潜伏期发生的丘脑-皮质电路进行成像。神经探针的配置限制了丘脑活动的定位精度为1.3 - 1.7 mm。
Electrical impedance tomography (EIT) is a technique that can reconstruct conductivity changes in a volume from multiple transfer impedance measurements. Impedance changes associated with neuronal depolarisation can be measured and hence the use of EIT as a functional brain imaging technique has been proposed. The work presented has sought to extend EIT in the rat model from an exclusively cortical imaging technique to one sensitive to subcortical activity. Chapter 1 provides an introduction to the principles of EIT and an overview of previous EIT experiments. Chapters 2 and 3 have focused on optimising parameters for imaging subcortical activity when using cortical electrode arrays. In chapter 2, EIT protocol generation methods aimed at enhancing sensitivity to deep regions of interest in the brain were developed. The protocol that maximised the magnitude of current density was found to be optimal. The best frequency at which to conduct EIT measurements was determined in chapter 3 by characterising the impedance response in the thalamus and cortex during somatosensory stimulation using carrier frequencies up to 10 kHz. The largest SNR in both the cortex and thalamus was observed at 1475 Hz. The ability to image ascending neural activity with cortical electrodes was investigated in chapter 4. Despite using the optimised parameters found previously, the small amplitude signals from the thalamus precluded imaging deeper than the cortex. Subsequent simulations indicated that with this type of electrode, EIT imaging is limited to 2.6 mm below the cortical surface. In chapter 5, the feasibility of conducting EIT measurements with neural probes was assessed. By implementing neural probes along with cortical electrode arrays, thalamo-cortical circuitry occurring at the correct latency during somatosensory stimulation was imaged. The con guration of neural probe implemented limited the localisation accuracy of thalamic activity to 1.3 1.7 mm.