Center for Information and Neural Networks, National Institute of Information and Communications Technology, Osaka, Japan.
Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
Hum Brain Mapp. 2020 May;41(7):1754-1764. doi: 10.1002/hbm.24907. Epub 2020 Jan 10.
Given that the brain is a dynamic system, the temporal characteristics of brain function are important. Previous functional magnetic resonance imaging (fMRI) studies have attempted to overcome the limitations of temporal resolution to investigate dynamic states of brain activity. However, finding an fMRI method with sufficient temporal resolution to keep up with the progress of neuronal signals in the brain is challenging. This study aimed to detect between-hemisphere signal progression, occurring on a timescale of tens of milliseconds, in the ventral brain regions involved in face processing. To this end, we devised an inter-stimulus interval (ISI) stimulation scheme and used a 7T MRI system to obtain fMRI signals with a high signal-to-noise ratio. We conducted two experiments: one to measure signal suppression depending on the ISI and another to measure the relationship between the amount of suppression and the ISI. These two experiments enabled us to measure the signal transfer time from a brain region in the ventral visual stream to its counterpart in the opposite hemisphere through the corpus callosum. These findings demonstrate the feasibility of using fMRI to measure ultra-fast signals (tens of milliseconds) and could facilitate the elucidation of further aspects of dynamic brain function.
鉴于大脑是一个动态系统，脑功能的时间特征很重要。先前的功能磁共振成像 (fMRI) 研究试图克服时间分辨率的限制，以研究大脑活动的动态状态。然而，找到一种具有足够时间分辨率的 fMRI 方法来跟上大脑中神经元信号的进展是具有挑战性的。本研究旨在检测参与面部处理的腹侧脑区中数十毫秒时间尺度的半球间信号进展。为此，我们设计了一种刺激间间隔 (ISI) 刺激方案，并使用 7T MRI 系统获得具有高信噪比的 fMRI 信号。我们进行了两项实验：一项是测量 ISI 依赖性的信号抑制，另一项是测量抑制量与 ISI 之间的关系。这两项实验使我们能够通过胼胝体测量腹侧视觉流中的一个脑区到对侧半球的对应脑区的信号传递时间。这些发现表明使用 fMRI 测量超快信号（数十毫秒）是可行的，并且可以促进对动态脑功能的进一步方面的阐明。
