Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan.
Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan.
Neuroscience. 2018 Feb 10;371:346-370. doi: 10.1016/j.neuroscience.2017.12.008. Epub 2017 Dec 12.
Magnetic stimulation is widely used in neuroscience research and clinical treatment. Despite recent progress in understanding the neural modulation mechanism of conventional magnetic stimulation methods, the physiological mechanism at the cortical microcircuit level is not well understood due to the poor stimulation focality and large electric artifact in the recording. To overcome these issues, we used a sub-millimeter-sized coil (micro-coil) to stimulate the mouse auditory cortex in vivo. To determine the mechanism, we conducted the first direct electrophysiological recording of micro-coil-driven neural responses at multiple sites on the horizontal surface and laminar areas of the auditory cortex. The laminar responses of local field potentials (LFPs) to the magnetic stimulation reached layer 6, and the spatiotemporal profiles were very similar to those of the acoustic stimulation, suggesting the activation of the same cortical microcircuit. The horizontal LFP responses to the magnetic stimulation were evoked within a millimeter-wide area around the stimulation coil. The activated cortical area was dependent on the coil orientation, providing useful information on the effective position of the coil relative to the brain surface for modulating cortical circuitry activity. In addition, numerical calculation of the induced electric field in the brain revealed that the inhomogeneity of the horizontal electric field to the surface is critical for micro-coil-induced cortical activation. The results suggest that our micro-coil technique has the potential to be used as a chronic, less-invasive and highly focal neuro-stimulator, and is useful for investigating microcircuit responses to magnetic stimulation for clinical treatment.
磁刺激在神经科学研究和临床治疗中得到了广泛应用。尽管最近在理解传统磁刺激方法的神经调节机制方面取得了进展，但由于记录中的刺激聚焦性差和大的电伪影，皮质微电路水平的生理机制仍不清楚。为了克服这些问题，我们使用亚毫米大小的线圈（微线圈）在体内刺激小鼠听觉皮层。为了确定机制，我们在听觉皮层的水平表面和层区域的多个位点进行了首次直接电生理记录微线圈驱动的神经反应。局部场电位（LFPs）对磁刺激的层响应达到第 6 层，时空分布与声刺激非常相似，表明激活了相同的皮质微电路。水平 LFP 对磁刺激的响应是在刺激线圈周围一毫米宽的区域内诱发的。被激活的皮质区域取决于线圈的方向，为调节皮质电路活动的线圈相对于大脑表面的有效位置提供了有用的信息。此外，对大脑中诱导电场的数值计算表明，表面水平电场的非均匀性对于微线圈诱导的皮质激活至关重要。结果表明，我们的微线圈技术有可能成为一种慢性、微创和高度聚焦的神经刺激器，可用于研究磁刺激对临床治疗的微电路反应。
