TMS stimulus-response asymmetry in lower limbs : Difference in stimulated muscles between dominant and non-dominant leg

Sammanfattning: Transcranial magnetic stimulation (TMS) is a 37-year-old non-invasive tool and can be used for diagnostic, therapeutics, and research purposes. In research, TMS is mostly used to stimulate the motor cortex, resulting in a neuroelectric excitatory response called a motor evoked potential (MEP). The resulting nerve signal leads to muscle movement, which can be measured by electromyography (EMG). Majority of previous research has targeted muscles of the upper limbs, due to the relative inaccessibility of the cortical leg area. Thus, the aim of this study is to investigate whether asymmetry occurs during lower limb stimulation and if there is a difference in stimulated muscles between dominant and non-dominant leg. Nine healthy adults conducted cortical stimulation over the motor cortex using double cone coil. EMG was recorded from the rectus femoris, tibialis anterior and abductor hallucis on both left and right leg. Depending on the subject's tolerance, data was collected by delivering 30 or 35 pulses. For each intensity, five MEPs were recorded, starting at 30% of the intensity and increasing in steps of 10%. Results showed no significant difference (p>0,05) between the dominant and non-dominant leg in all three muscles. In conclusion, the study no stimulus response asymmetry between the dominant and non-dominant leg in the respective muscle.