Complex-pattern evoked somatosensory responses in the study of multiple sclerosis

Three approaches are described for investigation of human somatosensory evoked responses in normal subjects and in multiple sclerosis patients. To median-nerve stimulation, the cortical evoked response (SER) reveals components whose shapes and latencies may be altered as a consequence of the disease. The use of periodic trains of stimuli (SERT) demonstrates that the oscillatory response of the nervous system deteriorates with advancing disease. Finally, the use of functional power series to characterize the somatosensory modality shows that responses to temporally interactive stimuli are nonlinear, decrease with increasing rate, and degenerate in the advanced state of the disease.