Evaluation of the position resolution of NIR topography by localised visual stimulation

Near-infrared (NIR) topography has been applied to the measurement of brain activation. However the position resolution of optical topography is not sufficient to measure focal brain activation. Since the localization of the brain activation in visual cortex depends on the visual stimuli position, it is difficult to resolve the localized brain activation in the visual cortex by NIR topography. In this study, we measured the localised brain activation evoked by visual stimulation to evaluate the position resolution of NIR topography with the high-density probe arrangement. The topographic image is obtained without solving inverse problem to investigate the effect of the high-density probe arrangement on improvement of the position resolution of NIR topography. When the brain activations evoked by the broad visual stimuli such as the whole checker boards, the topographic image measured with the single-density arrangement is almost the same as that with the double-density arrangement. The double-density arrangement effectively improves the topographic image when the brain activations were evoked by the localized visual stimuli such as the fanshaped checker boards.