三次元磁界計測に基づく生体信号の時間 : 周波数解析  [in Japanese] Time-Frequency Analysis of Biomagnetic Signals Based on 3-D Mangetic Field Measurement  [in Japanese]

We maeasured 3-D magnetoencephalograms (MEGs) of the magnetic fields evoked by somatosensory, auditory, and mixed stimulation of a human brain. The mixed stimulation consisted of auditory stimulation (AEF) and somatosensory stimulation (SEF). 3-D MEG measurement was carried out by using a 3-D second-order gradiometer with 39 channels, which can simultaneously detect magnetic field components perpendicular and tangential to the scalp. In order to estimate source localization in a human brain by using frequency information, a short-term spectrua of these measured data were calculated by using an autoregressive (AR) model, and a time change in the power spectrum was analyzed (time-frequency analysis). It was found that time-frequency analysis is a useful method for estimating multiple sources overlapping in time.