抄録
We measured somatosensory evoked fields (SEFs) by electric stimulus to the right posterior tibial nerve of three subjects, using a three-dimensional, second-order gradiometer connected to 39-channel SQUIDs, which can simultaneously detect the magnetic field components perpendicular to the scalp (Br) and tangential to the scalp (Bθ, Bφ).
In order to examine the relation between phase lag and stimulus repetition frequency (SRF), we detected the delay time of a component synchronous with interstimulus interval (29 to 501 ms) by convolution of the reference signal and SEF wave. Phase lag was linear to SRF for at least three different SRFs in all components. It was tested for significance using the linear regression slope (β≠0:p<0.05). The singular value decomposition (SVD) method was applied to each set of spatiotemporal SEF data. It was found that response latencies calculated by the slope of each component corresponded with the SEF latencies.
