Recently, measurement of the hemodynamic changes with functional image of near-infrared spectroscopy (NIRS), so-called functional optical tomography (fOT), has become a powerful tool for detecting the neuronal activity of brain with oxygenation dynamic measurement. Functional optical topography method provides several benefits such as less expensive, non-ionizing radiation imaging, real-time measurement, long time monitoring and easy operation [12–15]. Although the spatial resolution of fOT is quite limited, it still takes the own advantages for brain imaging. For example, the high temporal resolution (100 Hz or higher) of fOT methods prevents aliasing of higher frequency cardiac or respiratory activity, which is a significant component of variance in spontaneous BOLD signals of fMRI [16–18]. Therefore, fOT offers a more comprehensive measurement of brain activity than BOLD fMRI [19]. Additionally, fOT imaging offers completely patient-oriented measurement with undisturbed condition in resting-state.
