Intra‐cortical excitability in healthy human subjects after tongue training

Abstract

Training of specific muscles causes plastic changes in corticomotor pathways which may underlie the effect of various clinical rehabilitation procedures. The paired pulse transcranial magnetic stimulation (ppTMS) technique can be used to assess short interval intra-cortical inhibitory (SICI) and intra-cortical facilitatory (ICF) networks. This study examined changes in SICI and ICF in tongue motor cortex after tongue training in 11 healthy volunteers using ppTMS. Paired pulse TMS was applied to the 'hot-spot' for the tongue motor cortex and motor-evoked potentials (MEPs) were recorded from tongue muscles. In tongue motor cortex, bilateral SICI (P < 0.019) and ICF (P < 0.001) was detected before and after training. There were no significant effects of training on single MEPs or SICI/ICF (P > 0.063). The success rate improved during training (P < 0.001) and changes in success were correlated to changes in single MEP amplitude (P < 0.006) but not to SICI/ICF (P > 0.113). This first study of SICI/ICF after tongue training showed no training-related changes in intra-cortical inhibitory or facilitatory networks. However, there was an association between task performance and changes in corticomotor excitability. Further studies are required to determine the clinical utility of muscle specific training for oral rehabilitation purposes.

Force and complexity of tongue task training influences behavioral measures of motor learning

“…Previous studies have examined corticomotor control of tongue movements (4, 14). A series of tongue‐training studies performed by our group have revealed training‐induced neuroplasticity in human corticomotor control of the tongue by demonstrating an increase in motor‐evoked potentials produced by transcranial magnetic stimulation, as well as an increase in the motor cortex (MI) tongue representation (14–17). These studies have all used a highly standardized tongue‐protrusion task with a constant target force and timing of the task (rise time (protrude tongue), top delay (hold tongue protrusion force), fall time (retract tongue), and bottom delay (rest)) (14–16, 18, 19).…”

Bilateral sensory deprivation of trigeminal afferent fibres on corticomotor control of human tongue musculature: a preliminary study

“…TMS applied to the scalp between 8-9 cm lateral and 2-3 cm anterior to the interauricular line produced clear MEP responses with latencies between 6 and 10 ms in the tongue musculature of all the participants (5,24). The motor thresholds ranged between 31 and 56% (45Á9 AE 2Á4%) of maximum magnetic stimulator output for the tongue motor cortex.…”

“…It is also evident that peripheral somatosensory input is necessary in acquisition of new oro-facial motor skills (4). In humans, increase in cortical excitability of the tongue motor cortex (MI) has been reported after different tongue training tasks (5)(6)(7)(8)(9) and also following unilateral local anaesthesia (LA) of the tongue (1) and perioral region (10) compared to the first dorsal interosseous muscle (FDI) as a control. Relatively few studies have used transcranial magnetic stimulation (TMS) to examine the control of the tongue musculature (1,5,(11)(12)(13)(14) as well as few studies have attempted to study the modulation of tongue motor evoked potentials (MEPs) (1,5,7,15).…”

Neuroplasticity of face sensorimotor cortex and implications for control of orofacial movements

“…These neuroplastic changes are associated with significantly improved successful task performance. However, training may not be associated with changes in intra-cortical inhibitory or facilitatory networks [118]. Sensory perturbation induced by experimental intraoral noxious stimulation concomitantly prevents both successful tongue-task performance and the increased tongue-MI excitability associated with the task training ( Fig.…”