title: Tongue representation in the lateral cortical motor region of the human brain as assessed by transcranial magnetic stimulation.
abstract: Motor evoked potentials (MEPs) of the lingual muscles elicited by focal cortical transcranial magnetic stimulation (TMS) with a figure 8-shaped coil were investigated in 17 healthy subjects with special regard to amplitude and onset latency as a function of the coil position on the head surface. Bilateral reproducible responses could be observed at coil positions mostly varying from approximately 6 to 13 cm lateral to the vertex. During moderate muscle activation, maximum responses were obtained at a mean stimulus position of about 11 cm lateral and 3 cm anterior to the vertex with similar onset latencies, but with significantly higher amplitudes on the contralateral side (3.5 +/- 1.9 mV, 9.5 +/- 1.1 ms contralateral; 2.6 +/- 1.5 mV, 9.7 +/-1.0 ms ipsilateral). Comparing our data on the orbicularis oculi muscle with the results obtained on lower lip muscles, we found a considerable overlap of those coil positions from which reproducible MEPs could be elicited in both groups of target muscles, but the lingual area was placed more laterally. Thus, a statistically significant separation of the cortical representation areas of lingual and lower lip mimetic muscles is possible by focal cortical TMS, reflecting somatotopic organization of the face-associated motor cortex.
authors.affiliation: Department of Otorhinolaryngology, University of Göttingen, Göttingen, Germany.
authors.forename: Ralph M W
authors.initials: RM
authors.lastname: Rödel
authors.forename: Rainer
authors.initials: R
authors.lastname: Laskawi
authors.forename: Holger
authors.initials: H
authors.lastname: Markus
mesh_terms: D000328:Adult; D001931:Brain Mapping; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005152:Facial Muscles / Q000294:innervation / Q000502:physiology; D005154:Facial Nerve / Q000502:physiology; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007002:Hypoglossal Nerve / Q000502:physiology; D008046:Lip / Q000294:innervation / Q000502:physiology; D008297:Male; D008962:Models, Theoretical; D009044:Motor Cortex / Q000502:physiology*; D014059:Tongue / Q000294:innervation* / Q000502:physiology