We measured somatosensory evoked fields (SEFs) by giving electric stimulus to the right finger (medium nerve) with a 39-channel SQUID system, which can measure magnetic-field components perpendicular (Br) and tangential to the scalp (Bθ ,Bφ) simultaneously. Singular value decomposition (SVD) was applied to the measured SEF data for preprocessing (noise reduction). The delay time of a component synchronized with the SRFs was calculated by convoluting the reference signal and the measured SEF to investigate the relationship between phase lag and stimulus repetition frequency (SRF). We obtained latency of SEFs. We applied least-square method to each SEF components to obtain SEF function. Finally we modeled each SEF responses. We presented that characteristic of latency of SEFs by using electronic circuit.
