The Extraction And Analysis Of Somatosensory Evoked Potential

It is useful to research the change of human's evoked potential (EP)during illness. Many kinds of stimulus can evoke EP, and somatosensoryevoked potential can reflect integral function of spinal cord and centre nervesystem.In order to evoke somatosensory EP, a new current stimulator wasdesigned, which produces pulse current to stimulate trunk and limb of patients.For the safety of object, an isolated high-voltage power supply was used, andall the signals were isolated by optical coupling circuit. Parameters of thestimulator can be easily controlled by computer.Because the intensity of somatosensory EP is too low to extract, thetechniques of coherent average and analysis in frequency domain wereintroduced, and the differences between them were also presented.Experiment system of somatosensory EP can be built based on thecurrent stimulator and electroencephalograph. The stimulus artifact during theexperiment was discussed, and some methods were used to reduce the artifact.After processing of EEG data, transient-state somatosensory EP was extractedby coherent average and steady-state somatosensory EP was extracted byanalysis in frequency domain. The map of steady-state somatosensory EP canbe drawn by the combination of analysis in frequency domain and brainelectrical activity mapping (BEAM). The map can show the distribution of EPin the cortex, and the distribution was the result of source activities in humanbrain. Theory and results all can show that, analysis of somatosensory EP isan effective way to research human brain.