Abstract Background Neuroimaging technology is being developed to enable non-invasive mapping of the latency distribution of cortical projection pathways in white matter, and correlative clinical neurophysiological techniques would be valuable for mutual verification. Interhemispheric interaction through the corpus callosum can be measured with interhemispheric facilitation and inhibition using transcranial magnetic stimulation. Objective To develop a method for determining the latency distribution of the transcallosal fibers with transcranial magnetic stimulation. Methods We measured the precise time courses of interhemispheric facilitation and inhibition with a conditioning-test paired-pulse magnetic stimulation paradigm. The conditioning stimulus was applied to the right primary motor cortex and the test stimulus was applied to the left primary motor cortex. The interstimulus interval was set at 0.1 ms resolution. The proportions of transcallosal fibers with different conduction velocities were calculated by measuring the changes in magnitudes of interhemispheric facilitation and inhibition with interstimulus interval. Results Both interhemispheric facilitation and inhibition increased with increment in interstimulus interval. The magnitude of interhemispheric facilitation was correlated with that of interhemispheric inhibition. The latency distribution of transcallosal fibers measured with interhemispheric facilitation was also correlated with that measured with interhemispheric inhibition. Conclusions The data can be interpreted as latency distribution of transcallosal fibers. Interhemispheric interaction measured with transcranial magnetic stimulation is a promising technique to determine the latency distribution of the transcallosal fibers. Similar techniques could be developed for other cortical pathways.

中文翻译：

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使用经颅磁刺激测量经胼胝体纤维的潜伏期分布

摘要 背景 正在开发神经影像技术，以实现对白质中皮层投射通路的潜伏期分布的非侵入性映射，相关的临床神经生理学技术将有助于相互验证。通过胼胝体的半球间相互作用可以通过使用经颅磁刺激的半球间促进和抑制来测量。目的建立经颅磁刺激确定经胼胝体纤维潜伏期分布的方法。方法我们使用条件反射测试配对脉冲磁刺激范例测量了半球间促进和抑制的精确时间过程。条件刺激应用于右侧初级运动皮层，测试刺激应用于左侧初级运动皮层。刺激间隔设置为 0.1 ms 分辨率。通过测量半球间促进和抑制的大小随刺激间隔的变化计算具有不同传导速度的经胼胝体纤维的比例。结果随着刺激间隔的增加，半球间易化和抑制均增加。半球间易化程度与半球间抑制程度相关。用半球间促进测量的经胼胝体纤维的潜伏期分布也与用半球间抑制测量的分布相关。结论 该数据可以解释为经胼胝体纤维的潜伏期分布。用经颅磁刺激测量的半球间相互作用是确定经胼胝体纤维潜伏期分布的一种很有前途的技术。可以为其他皮质通路开发类似的技术。