A recently developed 24-channel optical topography (OT) system, that uses intensity-modulated near-infrared spectroscopy (NIRS) at wavelength of 780 nm and 830 nm can be used to visualize spatiotemporal changes of blood oxygenation states in human brain caused by cortical activity. We have used this system to estimate the hemodynamic changes during a language function task. To stimulate language function in the brain, we had a subject perform a writing task, which is more demanding than a speaking task. The subject, who was relaxed and sitting in a chair, was shown a card with a picture of an object for 3 seconds. During the 3 seconds, the subject wrote down the name of the object. The task was repeated 30 times, so the total stimulation period was 90 seconds. As a control task, the subject was shown figures with no meaning and drew each figure. The control task was performed as pre-stimulation for 60 seconds and as post-stimulation for 70 seconds, respectively. The subject rested for 30 seconds between post-stimulation and pre-stimulation. We observed a significant increase in the blood volume, which is proportional to the total change in the oxy-hemoglobin and deoxy-hemoglobin concentrations in the spatiotemporal topographic images in the area corresponding to Broca's area.