Parameters of motor evoked potentials in humans under transcutaneous electrical and electromagnetic stimulation of different segments of spinal cord

It's known that spinal interneuron networks have a significant effect on human locomotion. These networks are usually called central pattern generators for locomotion. It has been proved that remote non-invasive activation of these networks is possible in a number of ways. The parameters of motor evoked potentials (MEP) caused by different activation types have specific features. Previously we studied the peculiarities of spinal cord neuronal networks activation at T11-T12 level. At that stage, we studied the characteristics of MEP parameters under different spinal cord segments stimulation. We used the method of transcutaneous electrical nerve stimulation (TENS) and electromagnetic stimulation (EMS) of the spinal cord. Method of univariate analysis for repeated measurements was applied for statistical data processing (ANOVA). Some MEP parameters had significant differences under rostral and caudal segments stimulation of the lumbar enlargement. Thus, thresholds of muscles activation under TENS of rostral and caudal segments differed greatly. The MEP latency during TENS of rostral and caudal segments was the same but it changed under EMS influence. MEP latency did not changed under different types of stimulation, but depended on the stimulation location. MEP amplitude under TES significantly exceeded the similar values under EMS. MEP thresholds of upper limb muscles during both types of cervical segment stimulation were significantly lower than those of the lower limbs muscular responses, caused by stimulation of the lumbar enlargement. MEP amplitude of the majority of upper limb muscles during stimulation at C7-T1 level was significantly higher under TES than under EMS. Thus, MEP parameters depend on the type of stimulation and its location.