Transcranial electric and magnetic stimulation of the leg area of the human motor cortex: single motor unit and surface EMG responses in the tibialis anterior muscle. 1993

A Priori, and L Bertolasi, and D Dressler, and J C Rothwell, and B L Day, and P D Thompson, and C D Marsden
MRC Human Movement and Balance Unit, Institute of Neurology, London, UK.

We compared single motor unit and surface EMG responses in the active right tibialis anterior following anodal electrical or magnetic stimulation of the motor cortex over the vertex. Magnetic stimulation used a monophasic current pulse through a circular coil centred 3 cm anterior to the vertex. Lowest threshold magnetic stimulation occurred when the current in the coil flowed from the left to the right side at the posterior rim of the coil. Such stimulation produced single unit and surface EMG responses which had the same latency as those produced by anodal electric stimulation. If the direction of the magnetic stimulating current was reversed, response latencies became more variable from unit to unit, and on average they occurred 1.0 +/- 0.5 msec later. In single motor units anodal and magnetic post-stimulus time histogram (PSTH) peaks had the same duration. This was similar to the duration of the PSTH peaks produced by a single low intensity stimulus given to the common peroneal nerve. We conclude that magnetic stimulation can produce direct activation of corticospinal neurones to the tibialis anterior if the direction of induced current flow is optimal. This projection is likely to be either monosynaptic or oligosynaptic.

UI MeSH Term Description Entries
D007866 Leg The inferior part of the lower extremity between the KNEE and the ANKLE. Legs
D008280 Magnetics The study of MAGNETIC PHENOMENA. Magnetic
D009044 Motor Cortex Area of the FRONTAL LOBE concerned with primary motor control located in the dorsal PRECENTRAL GYRUS immediately anterior to the central sulcus. It is comprised of three areas: the primary motor cortex located on the anterior paracentral lobule on the medial surface of the brain; the premotor cortex located anterior to the primary motor cortex; and the supplementary motor area located on the midline surface of the hemisphere anterior to the primary motor cortex. Brodmann Area 4,Brodmann Area 6,Brodmann's Area 4,Brodmann's Area 6,Premotor Cortex and Supplementary Motor Cortex,Premotor and Supplementary Motor Cortices,Anterior Central Gyrus,Gyrus Precentralis,Motor Area,Motor Strip,Precentral Gyrus,Precentral Motor Area,Precentral Motor Cortex,Premotor Area,Premotor Cortex,Primary Motor Area,Primary Motor Cortex,Secondary Motor Areas,Secondary Motor Cortex,Somatic Motor Areas,Somatomotor Areas,Supplementary Motor Area,Area 4, Brodmann,Area 4, Brodmann's,Area 6, Brodmann,Area 6, Brodmann's,Area, Motor,Area, Precentral Motor,Area, Premotor,Area, Primary Motor,Area, Secondary Motor,Area, Somatic Motor,Area, Somatomotor,Area, Supplementary Motor,Brodmann's Area 6s,Brodmanns Area 4,Brodmanns Area 6,Central Gyrus, Anterior,Cortex, Motor,Cortex, Precentral Motor,Cortex, Premotor,Cortex, Primary Motor,Cortex, Secondary Motor,Cortices, Secondary Motor,Gyrus, Anterior Central,Gyrus, Precentral,Motor Area, Precentral,Motor Area, Primary,Motor Area, Secondary,Motor Area, Somatic,Motor Areas,Motor Cortex, Precentral,Motor Cortex, Primary,Motor Cortex, Secondary,Motor Strips,Precentral Motor Areas,Precentral Motor Cortices,Premotor Areas,Primary Motor Areas,Primary Motor Cortices,Secondary Motor Area,Secondary Motor Cortices,Somatic Motor Area,Somatomotor Area,Supplementary Motor Areas
D009046 Motor Neurons Neurons which activate MUSCLE CELLS. Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009132 Muscles Contractile tissue that produces movement in animals. Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D011712 Pyramidal Tracts Fibers that arise from cells within the cerebral cortex, pass through the medullary pyramid, and descend in the spinal cord. Many authorities say the pyramidal tracts include both the corticospinal and corticobulbar tracts. Corticobulbar Tracts,Corticospinal Tracts,Decussation, Pyramidal,Corticobulbar Tract,Corticospinal Tract,Pyramidal Decussation,Pyramidal Tract,Tract, Corticobulbar,Tract, Corticospinal,Tract, Pyramidal,Tracts, Corticobulbar,Tracts, Corticospinal,Tracts, Pyramidal
D011930 Reaction Time The time from the onset of a stimulus until a response is observed. Response Latency,Response Speed,Response Time,Latency, Response,Reaction Times,Response Latencies,Response Times,Speed, Response,Speeds, Response
D012016 Reference Values The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality. Normal Range,Normal Values,Reference Ranges,Normal Ranges,Normal Value,Range, Normal,Range, Reference,Ranges, Normal,Ranges, Reference,Reference Range,Reference Value,Value, Normal,Value, Reference,Values, Normal,Values, Reference
D004558 Electric Stimulation Use of electric potential or currents to elicit biological responses. Stimulation, Electric,Electrical Stimulation,Electric Stimulations,Electrical Stimulations,Stimulation, Electrical,Stimulations, Electric,Stimulations, Electrical
D004576 Electromyography Recording of the changes in electric potential of muscle by means of surface or needle electrodes. Electromyogram,Surface Electromyography,Electromyograms,Electromyographies,Electromyographies, Surface,Electromyography, Surface,Surface Electromyographies

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