MEASUREMENT OF HEMODYNAMICS OF AUDITORY-CORTEX USING MAGNETOENCEPHALOGRAPHY AND NEAR-INFRARED SPECTROSCOPY

Near infrared (NIR) spectroscopy, a non-invasive optical method for mo nitoring hemodynamics, was applied to record evoked auditory response of the human brain. Our newly developed system detected the amount of oxygenated and deoxygenated hemoglobin in the area of the local brain located beneath the probes. In the study, we used magnetoencephalograp hy (MEG) and NIR spectroscopy to observe the blood component change ne ar the auditory cortex. The sound stimulus of 1 kHz sine wave at 70 dB SPL was used to elicit evoked responses in both experiments. The acti ve region of the auditory cortex was determined by MEG, and the same a rea was examined by the NIR system. The results from the NTR experimen ts showed significant increases of total hemoglobin and deoxygenated h emoglobin, indicating that both blood flow and oxygen consumption at t he cortical area increased in response to the sound stimuli. The NIR r ecordings at the two different depths revealed that the increases of l ocal blood flow and oxygen consumption were observed at depths ranging between 20 and 30 mm from the scalp.