17. Spatial filter imaging of nerve electrical activities in the lumbar spine

The aim of this studywas to develop amethod for functional imaging of human nerve electrical activities in the lumbar spine from evoked neuromagnetic measurements. The source reconstruction of nerve electrical activities was carried out over a curved surface that contained the nerve fiber in the lumbar spine. This curved surface was determined by using subject’s lateral X-ray image. We proposed to apply the Unit-Gain Constraint MinimumNorm filter with a Recursively Update Gram matrix spatial filter to reconstruct source activities on this surface. Reconstructed source intensity reflected cauda equine travel. This linewas determined by using reconstructed source imaging of the front direction. Reconstructed sources propagated from caudal to rostral along the lumbar spinal canal. During the time courses at five selected voxels along the nerve travel, each time course showed a clear peak and into latency indicated the instants when nerve activity arrived at five voxel locations. Our proposed imaging method can clearly visualize the dynamics and the temporal intensity changes of nerve electrical activities in the lumbar spine.