Research articleModulation of quadriceps corticospinal excitability by femoral nerve stimulation

- The time course of MEP modulation induced by electrical stimulation is showed.
- Electrical stimulation of the femoral nerve induced a short latency inhibition.
- Long latency facilitation was evoked in the rectus femoris by TMS.

IntroductionWe explored the conditioning effect of a percutaneous electrical pulse of the femoral nerve on cortical motor evoked responses in the rectus femoris muscle.MethodsCorticospinal excitability of rectus femoris muscle was measured in sixteen healthy subjects, when a single transcranial magnetic pulse was preceded by an electrical femoral nerve stimulus, using twelve inter-stimulus intervals (from 10 to 275 ms). We also evaluated the effects of the intensities of the transcranial magnetic and of the electrical pulses.ResultsQuadriceps motor evoked potentials were inhibited and facilitated when a single femoral nerve electrical stimulus was delivered at inter-stimulus intervals of 25 ms and 150 ms, respectively. The facilitation was reduced when low electrical intensity was used, while the inhibition decreased with high intensity transcranial magnetic pulse.ConclusionAfferent inputs of a femoral stimulation modulate the responses elicited by transcranial magnetic pulses of the contralateral quadriceps motor cortex. This modulation indicates a sensorimotor integration of proximal lower limb muscles that may be mediated via different types of afferents. This could be of relevance for studies that explore the role of lower limb muscles in postural control and balance.