Accessibility of cortical regions to focal TES: Dependence on spatial position, safety, and practical constraints
Accessibility of cortical regions to focal TES: Dependence on spatial position, safety, and practical constraints
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DOI：
10.1016/j.neuroimage.2019.116183
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发表时间：
2019-12-01
期刊：
影响因子：
5.7
通讯作者：
Madsen, Kristoffer Hougaard
中科院分区：
文献类型：
--
作者：
Saturnino, Guilherme Bicalho;Siebner, Hartwig Roman;Madsen, Kristoffer Hougaard
经颅电刺激（TES）可以通过连接到头皮的电极注入微弱电流来调节大脑的内在神经活动。 TES 已被广泛用作神经科学工具，用于研究如何通过特定大脑区域的电刺激来调节大脑功能的行为和生理变量。为了对 TES 实验进行明确的解释，重要的是电场可以引导到一个或多个感兴趣的大脑区域。然而，人类头部的导电特性对多电极 TES 产生的大脑电场的聚焦程度施加了固有的物理限制。根据经验，利用 TES 选择性地瞄准大脑深部区域是不可行的，尽管由于周围组织有利的导电特性，将场聚焦在某些特定的更深位置是可能的。在本研究中，我们首先提出了一种计算有效的方法，用于自动确定电极放置和刺激强度，以最佳地影响给定的目标位置。我们提供了优化程序的稳健实现，能够遵守安全约束，同时明确控制有源电极的数量以及目标区域中场相对于所需场方向的角度偏差。利用我们方法的高计算效率，我们系统地评估了所有皮层位置的多电极 TES 可实现的焦点，从而研究对所选约束的依赖性。我们的结果提供了对可实现的 TES 剂量和焦点的限制的全面见解，这些限制是由生物物理限制和 TES 的安全考虑所造成的。
Transcranial electric stimulation (TES) can modulate intrinsic neural activity in the brain by injecting weak currents through electrodes attached to the scalp. TES has been widely used as a neuroscience tool to investigate how behavioural and physiological variables of brain function are modulated by electric stimulation of specific brain regions. For an unambiguous interpretation of TES experiments, it is important that the electric fields can be steered towards one or several brain regions-of-interest. However, the conductive proprieties of the human head impose inherent physical limitations on how focal the electric fields in the brain produced by multi-electrode TES can be. As a rule of thumb, it is not feasible to selectively target deep brain areas with TES, although focusing the field in some specific deeper locations might be possible due to favourable conductive properties in the surrounding tissue. In the present study, we first propose a computationally efficient method for the automatic determination of electrode placements and stimulation intensities to optimally affect a given target position. We provide a robust implementation of the optimization procedure that is able to adhere to safety constraints, while explicitly controlling both the number of active electrodes and the angular deviation of the field in the target area relative to the desired field direction. Leveraging the high computational efficiency of our method, we systematically assess the achievable focality of multi-electrode TES for all cortex positions, thereby investigating the dependence on the chosen constraints. Our results provide comprehensive insight into the limitations regarding the achievable TES dose and focality that are imposed by the biophysical constraints and the safety considerations of TES.