Influence of topical anaesthesia on the corticomotor response to tongue training.
OBJECTIVE
The aim of this experimental study was to investigate if perturbation of somatosensory function would change corticomotor excitability of the tongue musculature in relation to a novel tongue training task.


METHODS
Sixteen healthy volunteers participated in two randomized and double-blind sessions separated by two weeks, in which topical anaesthetics or placebo cream were applied to the tongue during a standardized tongue training task. Corticomotor excitability was assessed by changes in motor evoked potentials (MEPs) in the tongue musculature evoked by transcranial magnetic stimulation (TMS) before and after training.


RESULTS
The success rate of the training task increased in both sessions (relative increase: topical anaesthetics = 53 +/- 53%; placebo = 50 +/- 48%; P = 0.713). The MEP amplitudes increased with stimulation intensity (P < 0.026) in both sessions and there were significantly higher MEP amplitudes on the contralateral tongue muscle compared to the ipsilateral tongue (P < 0.019). There were no differences in MEP amplitudes between the topical anaesthetic and placebo session and there were no main effects of the tongue training task. However, there were significant correlations between increases in success rate and facilitation of the MEP amplitudes in the tongue muscles.


CONCLUSIONS
Topical anaesthesia has no major effects on corticomotor excitability of tongue musculature and there appears to be a strong individual variation in the effects of a tongue training task on MEP amplitudes.
Ernberg
Malin
M
Departments of Clinical Oral Physiology and Dental Medicine, Karolinska Institutet, SE 14104 Huddinge, Sweden. Malin.Ernberg@ki.se
Serra
Elena
E
Baad-Hansen
Lene
L
Svensson
Peter
P
D000328:Adult; D019162:Anesthetics, Combined / Q000008:administration & dosage; D000779:Anesthetics, Local / Q000008:administration & dosage*; D004311:Double-Blind Method; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005152:Facial Muscles / Q000502:physiology; D005260:Female; D006801:Humans; D007002:Hypoglossal Nerve / Q000502:physiology; D008012:Lidocaine / Q000008:administration & dosage; D000077442:Lidocaine, Prilocaine Drug Combination; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D009434:Neural Pathways / Q000187:drug effects; D009473:Neuronal Plasticity / Q000187:drug effects; D010919:Placebos; D011318:Prilocaine / Q000008:administration & dosage; D011930:Reaction Time / Q000502:physiology; D012683:Sensory Deprivation / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology; D014059:Tongue / Q000187:drug effects* / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014159:Transducers
D019162:Anesthetics, Combined; D000779:Anesthetics, Local; D000077442:Lidocaine, Prilocaine Drug Combination; D010919:Placebos; D011318:Prilocaine; D008012:Lidocaine