Tongue Force Research Articles

Pulmonary C-fiber activation attenuates respiratory-related tongue movements

The functional impact of pulmonary C-fiber activation on upper airway biomechanics has not been evaluated. Here, we tested the hypothesis that pulmonary C-fiber activation alters the respiratory-related control of tongue movements. The force produced by tongue movements was quantified in spontaneously breathing, anesthetized adult rats before and after stimulation of pulmonary C fibers via intrajugular delivery of capsaicin (0.625 and 1.25 μg/kg). Brief occlusion of the trachea was used to increase the respiratory drive to the tongue muscles, and hypoglossal (XII) nerve branches were selectively sectioned to denervate the protrusive and retrusive tongue musculature. Tracheal occlusion triggered inspiratory-related tongue retrusion in rats with XII nerves intact or following section of the medial XII nerve branch, which innervates the genioglossus muscle. Inspiratory-related tongue protrusion was only observed after section of the lateral XII branch, which innervates the primary tongue retrusor muscles. The tension produced by inspiratory-related tongue movement was significantly attenuated by capsaicin, but tongue movements remained retrusive, unless the medial XII branch was sectioned. Capsaicin also significantly delayed the onset of tongue movements such that tongue forces could not be detected until after onset of the inspiratory diaphragm activity. We conclude that altered neural drive to the tongue muscles following pulmonary C-fiber activation has a functionally significant effect on tongue movements. The diminished tongue force and delay in the onset of tongue movements following pulmonary C-fiber activation are potentially unfavorable for upper airway patency.

I08 System for measuring tongue force variability immune to head movements artifacts

System originally developed for Track-HD project (R Reilmann) due to externally opened force measuring chain, can be vulnerable to upper body and head movements, which may interfere with measured tongue force. The sensor housing is attached to the external frame against which subject suppose to rest during the measurement. The tongue pushing muscles (four extrinsic glossus muscles) are anchored in the bottom part of oral cavity. The housing of the force transducer should be attached to the same biomechanical structure which serves muscles anchoring. The most steady fixation surface provides the bite that allow comfortable holding of transducer between the teeth. Transducer housing has cylindrical form of 13 mm diameter with the butterfly plate at its top, preventing its slippage out of the mouth (a modified syringe). The opposite slotted tip of the syringe, serves as the bayonet connection, allowing to attach the force sensor in precisely centered position. Pushing force of the tongue, which always stays inside the mouth, is transmitted to the force sensor by the syringe plunger with removed sealed tip. To prevent the damage of the force sensor by applying the force above 45N, there is a short spring giving the transducer additional elasticity which passes to the excessive force to the sensor enclosure. Authors explored the possibility of characterising the tongue force instability with the single number parameter like the surface under the rectified AC force signal, as well as the number of crossings the line of required force level. Force transducer may be connected to the universal data acquisition system originally developed for measuring saccadic eye movements.

Tongue force and tongue motility are differently affected by unilateral vs bilateral nigrostriatal dopamine depletion in rats

In addition to its cardinal symptoms of bradykinesia, muscle rigidity, resting tremor and postural disturbances, Parkinson's disease (PD) also affects orolingual motor function. Orolingual motor deficits can contribute to dysphagia, which increases morbidity and mortality in this population. Previous preclinical studies describing orolingual motor deficits in animal models of PD have focused on unilateral nigrostriatal dopamine (DA) depletion. In this study we compared the effects of unilateral vs bilateral 6-hydroxydopamine (6-OHDA)-induced DA depletion in rats trained to lick water from an isometric force-sensing disc. Rats received either unilateral or bilateral 6-OHDA into the medial forebrain bundle and were tested for four weeks post-lesion. Dependent variables included task engagement (the number of licks per session), tongue force (mean and maximum), and tongue motility (the number of licks per second). While both lesion groups exhibited decreased tongue force output, tongue motility deficits were present in only the group that received unilateral nigrostriatal DA depletion. Task engagement was not significantly diminished by 6-OHDA. Analysis of striatal DA tissue content revealed that DA depletion was ∼97% in the unilateral group and ∼90% in the bilateral group. These results suggest that while nigrostriatal DA depletion affects tongue force output, deficits in tongue motility may instead result from a functional imbalance in neural pathways affecting this midline structure.

Measurement of infant tongue thickness using ultrasound: A technical note

Novel uses of ultrasound include obtaining images of intra-oral structures to further research in speech production and feeding. In this technical note we describe a noninvasive, cost-effective, and reliable method for measuring infant tongue muscle thickness. The current pilot study demonstrates high reliability of a trained ultrasonographer to obtain adequate images of the infant tongue and the ability to measure reliably between two anatomic landmarks to determine tongue thickness and investigate a potential relationship between tongue size and tongue force.

Influência de altura, peso e índice de massa corporal na força axial da língua

To analyze the influence of weight, height and body mass index in the axial tongue force. Medical records with data from 44 subjects aged between 20 and 37 years, 11 (25%) males and 33 (75%) female, were analyzed. The investigated information were weight, height, result of clinical evaluation for tongue force (lingual tonus) and instrumental assessment of axial tongue force, which was accomplished by using the FORLING. Data was statistically analyzed. No differences were observed between the force values regarding the variables body mass index classification and clinical classification of tongue force. Body mass index and weight had positive correlation with mean tongue force. There was a strong positive correlation between the variables mean force, maximum force and highest maximum force. Although body mass index and weight correlated positively with the mean axial tongue force, there was no association between body mass index classification and the axial tongue forces.

Clinical impairment in premanifest and early Huntington's disease is associated with regionally specific atrophy

TRACK-HD is a multicentre longitudinal observational study investigating the use of clinical assessments and 3-Tesla magnetic resonance imaging as potential biomarkers for future therapeutic trials in Huntington's disease (HD). The cross-sectional data from this large well-characterized dataset provide the opportunity to improve our knowledge of how the underlying neuropathology of HD may contribute to the clinical manifestations of the disease across the spectrum of premanifest (PreHD) and early HD. Two hundred and thirty nine gene-positive subjects (120 PreHD and 119 early HD) from the TRACK-HD study were included. Using voxel-based morphometry (VBM), grey and white matter volumes were correlated with performance in four domains: quantitative motor (tongue force, metronome tapping, and gait); oculomotor [anti-saccade error rate (ASE)]; cognition (negative emotion recognition, spot the change and the University of Pennsylvania smell identification test) and neuropsychiatric measures (apathy, affect and irritability). After adjusting for estimated disease severity, regionally specific associations between structural loss and task performance were found (familywise error corrected, P < 0.05); impairment in tongue force, metronome tapping and ASE were all associated with striatal loss. Additionally, tongue force deficits and ASE were associated with volume reduction in the occipital lobe. Impaired recognition of negative emotions was associated with volumetric reductions in the precuneus and cuneus. Our study reveals specific associations between atrophy and decline in a range of clinical modalities, demonstrating the utility of VBM correlation analysis for investigating these relationships in HD.

Tongue function in patients treated for malignancies in tongue and/or floor of mouth; a one year prospective study

Progress in (reconstructive) surgery and radiotherapy tends to improve survival and reduce oral functional deficits. Despite the growing sophistication of cancer treatment, patients still report deterioration in tongue function. Sensory function, mobility, and force of the tongue were determined in 45 patients with a carcinoma of tongue and/or floor of mouth. Measurements were performed before surgery, shortly after surgery, shortly after radiotherapy, 6, and 12 months after surgery. Surgery had a negative impact on tongue sensory function and mobility. Post-surgery radiotherapy did not further deteriorate sensory function, mobility, or force of the tongue. Patients in the surgery-radiotherapy group (SRG) had significantly worse tongue sensory function and mobility than patients in the surgery group (SG), probably caused by more advanced tumour stage and more extensive reconstructions and related scar tissue. The tongue force in patients in both groups significantly increased in the first 6 months after surgery, but this increase disappeared in the next 6 months. The authors conclude that surgery had a significant negative influence on tongue function, especially in the group of patients treated with radiotherapy. No further deterioration of tongue function was observed after post-surgical radiotherapy within the first year after surgery.

Sensorimotor function of the upper-airway muscles and respiratory sensory processing in untreated obstructive sleep apnea.

Numerous studies have demonstrated upper-airway neuromuscular abnormalities during wakefulness in snorers and obstructive sleep apnea (OSA) patients. However, the functional role of sensorimotor impairment in OSA pathogenesis/disease progression and its potential effects on protective upper-airway reflexes, measures of respiratory sensory processing, and force characteristics remain unclear. This study aimed to gain physiological insight into the potential role of sensorimotor impairment in OSA pathogenesis/disease progression by comparing sensory processing properties (respiratory-related evoked potentials; RREP), functionally important protective reflexes (genioglossus and tensor palatini) across a range of negative pressures (brief pulses and entrained iron lung ventilation), and tongue force and time to task failure characteristics between 12 untreated OSA patients and 13 controls. We hypothesized that abnormalities in these measures would be present in OSA patients. Upper-airway reflexes (e.g., genioglossus onset latency, 20 ± 1 vs. 19 ± 2 ms, P = 0.82), early RREP components (e.g., P1 latency 25 ± 2 vs. 25 ± 1 ms, P = 0.78), and the slope of epiglottic pressure vs. genioglossus activity during iron lung ventilation (-0.68 ± 1.0 vs. -0.80 ± 2.0 cmH(2)O/%max, P = 0.59) were not different between patients and controls. Maximal tongue protrusion force was greater in OSA patients vs. controls (35 ± 2 vs. 27 ± 2 N, P < 0.01), but task failure occurred more rapidly (149 ± 24 vs. 254 ± 23 s, P < 0.01). Upper-airway protective reflexes across a range of negative pressures as measured by electromyography and the early P1 component of the RREP are preserved in OSA patients during wakefulness. Consistent with an adaptive training effect, tongue protrusion force is increased, not decreased, in untreated OSA patients. However, OSA patients may be vulnerable to fatigue of upper-airway dilator muscles, which could contribute to disease progression.

Tongue force and timing deficits in a rat model of Parkinson disease

Deficits in tongue function in conjunction with airway compromise can contribute to dysphagia associated with Parkinson disease (PD). However, it is unknown if these deficits are related to the primary disease pathology in PD, nigrostriatal dopamine depletion. To directly study the impact of striatal dopamine depletion on tongue function, we used unilateral infusion of the neurotoxin 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle and measured tongue force and timing parameters during a complex tongue protrusion task for a water reward. Maximal and average forces were significantly diminished and average press time was significantly longer after neurotoxin administration, reflecting aspects of bradykinesia and hypokinesia associated with PD. Our findings suggest that even unilateral deficits to the nigrostriatal dopamine system may be contributing to some of the lingual sensorimotor deficits seen in PD. Because previous research in rat models of PD has shown that targeted training of the limb can rescue behavioral deficits and spare striatal dopamine neurons, early intervention for cranial sensorimotor deficits may also be indicated.

Quantitative evaluation of tongue protrusion force

The tongue plays an important role in the functions of speech, mastication, swallowing, and breathing. The tongue helps in the maintenance of proper dental alignment and arch stability. Adequate strength is essential for the tongue to perform these tasks. Recently the Biomechanical Engineering Group from Universidade Federal de Minas Gerais, Brazil, developed a device to improve tongue strength evaluation. The purpose of this study is to describe and compare the main results obtained in tongue protrusion force measurements in different age groups using this new device. Fifteen healthy subjects were given a qualitative evaluation and determined to have normal tongue strength. They were separated by age in three groups: children, adults and elderly. They were then given a quantitative evaluation. Maximum and average forces were analyzed. The time taken to reach maximum force was also assessed. Higher values of maximum and average tongue force were obtained in the adult group, followed by the elderly group and the group of children. Older subjects had greater tongue force when compared to children. However, there were statistically significant differences in the average force and in the maximum force only between children and adults. Time taken to reach maximal isometric force was longer in the elderly group and shorter in the group of children than in the group of adults although no statistically significant difference was found between groups.

Functional Rescue of Dystrophin-deficient mdx Mice by a Chimeric Peptide-PMO

Splice modulation using antisense oligonucleotides (AOs) has been shown to yield targeted exon exclusion to restore the open reading frame and generate truncated but partially functional dystrophin protein. This has been successfully demonstrated in dystrophin-deficient mdx mice and in Duchenne muscular dystrophy (DMD) patients. However, DMD is a systemic disease; successful therapeutic exploitation of this approach will therefore depend on effective systemic delivery of AOs to all affected tissues. We have previously shown the potential of a muscle-specific/arginine-rich chimeric peptide-phosphorodiamidate morpholino (PMO) conjugate, but its long-term activity, optimized dosing regimen, capacity for functional correction and safety profile remain to be established. Here, we report the results of this chimeric peptide-PMO conjugate in the mdx mouse using low doses (3 and 6 mg/kg) administered via a 6 biweekly systemic intravenous injection protocol. We show 100% dystrophin-positive fibers and near complete correction of the dystrophin transcript defect in all peripheral muscle groups, with restoration of 50% dystrophin protein over 12 weeks, leading to correction of the DMD pathological phenotype and restoration of muscle function in the absence of detectable toxicity or immune response. Chimeric muscle-specific/cell-penetrating peptides therefore represent highly promising agents for systemic delivery of splice-correcting PMO oligomers for DMD therapy.

I04 Magnetic transfer imaging in premanifest and manifest Huntington's disease: results from the TRACK-HD study

BackgroundMagnetisation transfer imaging (MTI) has the potential to quantify pathological changes in CNS disorders before conventional MRI sequences can detect abnormalities. This makes MTI an attractive technique to apply in...

Tongue force analysis assesses motor phenotype in premanifest and symptomatic Huntington's disease

Motor symptoms in Huntington's Disease (HD) are commonly assessed by the Unified Huntington's Disease Rating Scale-Total Motor Score (UHDRS-TMS). However, the UHDRS-TMS is limited by interrater variability, its categorical nature, and insensitivity in premanifest subjects. More objective and quantitative measures of motor phenotype may complement the use of the UHDRS-TMS as outcome measure and increase the power and sensitivity of clinical trials. Deficits in tongue protrusion are well acknowledged in HD and constitute a subitem of the UHDRS-TMS. We, therefore, investigated whether objective and quantitative assessment of tongue protrusion forces (TPF) provides measures that (1) correlate to the severity of motor phenotype detected in the UHDRS-TMS in symptomatic HD, (2) detect a motor phenotype in premanifest HD gene-carriers, and (3) exhibit a correlation to the genotype as assessed by a disease burden score (based on CAG-repeat length and age). Using a precalibrated force transducer, the ability of premanifest gene carriers (n = 15) and subjects with symptomatic HD (n = 20) to generate and maintain isometric TPF at three target force levels (0.25, 0.5, and 1.0 N) was assessed and compared with age-matched controls (n = 20) in a cross-sectional study. Measures of variability of TPF and tongue contact time distinguished controls, premanifest, and symptomatic HD groups and correlated to the UHDRS-TMS and disease burden score, suggesting a strong genotype-phenotype correlation. Group distinction was most reliable at the lowest target force level. We conclude that assessment of TPF may be a useful objective and quantitative marker of motor dysfunction in premanifest and symptomatic HD.

Measures of bulbar and spinal motor function, muscle innervation, and mitochondrial function in ALS rats

Symptom onset in amyotrophic lateral sclerosis (ALS) may occur in the muscles of the limbs (spinal onset) or those of the head and neck (bulbar onset). Most preclinical studies have focused on spinal symptoms, despite the prevalence of and increased morbidity and mortality associated with bulbar disease. We measured lick rhythm and tongue force to evaluate bulbar disease in the SOD1-G93A rat model of familial ALS. Body weight and grip strength were measured concomitantly. Testing spanned the early (maturation), middle (pre-symptomatic), and late (symptomatic and end-stage) phases of the disease. We measured a persistent tongue motility deficit that became apparent in the early phase of the disease, providing behavioral evidence of bulbar pathology. At end-stage, however, cytochrome oxidase (CO) activity was normal in the hypoglossal nucleus, and in the tongue, neuromuscular innervation, citrate synthase (CS) protein levels and activity, and uncoupling protein 3 (UCP3) protein levels remained unchanged. Interestingly, significant denervation and atrophy were evident in the end-stage sternomastoid muscle, providing peripheral anatomical evidence of bulbar pathology. Changes in body weight and grip strength occurred in the late phase of the disease. Extensive atrophy and denervation were observed in the end-stage gastrocnemius muscle. In contrast to our findings in the tongue, CS protein levels were decreased in the extensor digitorum longus (EDL) and soleus, although CS activity was maintained or increased. UCP3 protein was decreased also in the EDL. These data provide evidence of differential effects in muscles that were more or less affected by disease.

Quantitative motor phenotype assessment in pre-manifest and symptomatic Huntington's disease: tongue force analysis differentiates between disease stages and provides high phenotype correlation. Cross sectional results from the TRACK-HD Study

Quantitative motor phenotype assessment in pre-manifest and symptomatic Huntington's disease: tongue force analysis differentiates between disease stages and provides high phenotype correlation. Cross sectional results from the TRACK-HD Study

In-Situ Mechanical Characteristics of the Tongue are not Altered in the Obese Zucker Rat

Obese Zucker rats have more collapsible isolated upper airways, compared with their lean counterparts. The functional characteristics of the tongue as a potential mechanism for the enhanced upper airway collapsibility in the obese Zucker rat are unknown. This study measured the functional characteristics of the tongue muscle in lean and obese Zucker rats. In-situ tongue force (twitch and peak) and fatigability were measured in anesthetized obese and lean Zucker rats. Animal housing facility at the University of Buffalo. Eight lean and eight obese Zucker rats. Tongue force and fatigability were measured before, during, and following cocontraction of the tongue protrudor and retractor muscles via direct stimulation of the common hypoglossal nerve. Obese rats were significantly heavier than their lean counterparts (718 +/- 101 gm vs. 545 +/- 32, P < 0.05). Total force production at all stimulation frequencies was not different between lean and obese Zucker rats before or after fatigue (P = 0.436). Forces were significantly reduced at the end of the 5-minute stimulation period (P < 0.001) and returned to baseline within 1 minute after fatigue in both lean and obese rats. At the end of the fatigue protocol, tongue force averaged 63.3% +/- 13.8% and 72.3% +/- 17.8% of the initial force in obese and lean rats respectively (P= 0.85). Obesity does not alter the in-situ force production of the tongue muscle. Thus, increases in collapsibility of the isolated upper airway previously noted in obese Zucker rats cannot be ascribed to upper airway muscle dysfunction or enhanced fatigability.

Effects of tongue force training on orolingual motor cortical representation

Previous research has demonstrated that training rats in a skilled reaching condition will induce task-related changes in the caudal forelimb area (CFA) of motor cortex. The purpose of the present study was to determine whether task-specific changes can be induced within the orofacial area of the motor cortex in rats. Specifically, we compared changes of the orofacial motor cortical representation in lick-trained rats to age-matched controls. For 1 month, six water-restricted Sprague–Dawley rats were trained to lick an isometric force-sensing disc at increasing forces for water reinforcement. The rats were trained daily for 6 min starting with forces of 1 g, and increasing over the course of the month to 10, 15, 20, 25 and finally 30 g. One to three days following the last training session, the animals were subjected to a neurophysiological motor mapping procedure in which motor representations corresponding to the orofacial and adjacent areas were defined using intracortical microstimulation (ICMS) techniques. We found no statistical difference in the topographical representation of the control (mean = 2.03 mm 2) vs. trained (1.87 mm 2) rats. This result indicates that force training alone is insufficient to drive changes in the size of the cortical representation. We also recorded the minimum current threshold required to elicit a motor response at each site of microstimulation. We found that the lick-trained rats had a significantly lower average minimum threshold (29.1 ± 1.0 μA) for evoking movements related to the task compared to control rats (34.6 ± 1.1 μA). These results indicate that while tongue force training alone does not produce lasting changes in the size of the orofacial cortical motor representation, tongue force training decreases the current thresholds necessary for eliciting an ICMS-evoked motor response.

Genioglossus and Intrinsic Electromyographic Activities in Impeded and Unimpeded Protrusion Tasks

Eight muscles invest the human tongue: four extrinsic muscles have external origins and insert into the tongue body and four intrinsic muscles originate and terminate within the tongue. Previously, we noted minimal activation of the genioglossus tongue muscle during impeded protrusion tasks (i.e., having subjects push the tongue against a force transducer), suggesting that other muscles play a role in the production of tongue force. Accordingly, we sought to characterize genioglossus tongue muscle activities during impeded and unimpeded protrusion tasks (i.e., having subjects slowly and smoothly move the tongue out of their mouth). Electromyographic (EMG) and single motor-unit potentials of the extrinsic genioglossus muscle were recorded with tungsten microelectrodes and EMG activities of intrinsic tongue muscles were recorded with hook-wire electrodes inserted into the anterior tongue body. Tongue position was detected by an isotonic transducer coupled to the tongue tip. Protrusive force was detected by a force transducer attached to a rigid bar. Genioglossus and intrinsic tongue muscles were simultaneously active in both impeded and unimpeded protrusion tasks. Genioglossus whole muscle EMG and single motor-unit activities changed faithfully as a function of tongue position, with increased discharge associated with protrusion and decreased discharge associated with retraction back to the rest position. In contrast, during the impeded protrusion task drive the genioglossus muscle remained constant as protrusion force increased. Conversely, intrinsic tongue muscle activities appropriately followed changes in both tongue position and force. Importantly, we observed significantly higher levels of intrinsic muscle activity in the impeded protrusion task. These observations suggest that protrusion of the human tongue requires activation of the genioglossus and intrinsic protrudor muscles, with the former more important for establishing anterior-posterior tongue location and the latter playing a greater role in the generation of protrusive force. A biomechanical model of these actions is provided and discussed.

WKA-1R Robot assisted quantitative assessment of airway management

The emerging field of medical robotics aims tointroduce intelligent tools for physician support. The main challenges for developing efficient medical robotic training systems are simulating real-world conditions of the task and assuring training effectiveness. High anatomic fidelity has been achieved in current systems, but they are limited to provide merely subjective assessments of the training progress. We simulated airway intubation using a unique medical robot and developed objective performance criteria to assess task performance. A patient simulation robot was designed to mimic real-world task conditions and provide objective assessments of training progress. The Waseda– Kyotokagaku Airway No. 1R (WKA-1R) includes a human patient model with embedded sensors. An evaluation function was developed for the WKA-1R to quantitatively assess task performance. The evaluation includes performance indices and coefficient weighting. The performance indices were defined based on experiments carried out with medical doctors and from information found in the medical literature. The performance indices are: intubation time, jaw opening, incisor teeth force, cuff pressure, tongue force and tube position. To determine the weighting of coefficients, we used discriminant analysis. Experiments were carried out with volunteers to determine the effectiveness of the WKA-1R to quantitatively evaluate their performance while performing airway management. We asked subjects from different levels of expertise (from anesthetists to unskilled) to perform the task. From the experimental results, we determined operator effectiveness using the proposed performance indices. We found a significant difference between the experimental groups by evaluating their performances using the proposed evaluation function (P < 0.05). The WKA-1R robot was designed to quantitatively acquire information on the performances of trainees during intubation procedures. From the experimental results, we could objectively determine operator effectiveness while providing quantitative task assessments.

Effect of Tongue Exercise on Protrusive Force and Muscle Fiber Area in Aging Rats

Age-related changes in tongue function may contribute to dysphagia in elderly people. The authors' purpose was to investigate whether aged rats that have undergone tongue exercise would manifest increased protrusive tongue forces and increased genioglossus (GG) muscle fiber cross-sectional areas. Forty-eight young adult, middle-aged, and old Fischer 344/Brown Norway rats received 8 weeks of tongue exercise. Protrusive tongue forces were measured before and after exercise. GG muscle fiber cross-sectional area was measured in exercised rats and was compared with cross-sectional areas in a no-exercise control group. A significant increase in maximum tongue force was found following exercise in all age groups. In addition, a trend for increased GG muscle fiber cross-sectional area and a significant increase in variability of GG muscle fiber cross-sectional area was identified postexercise. The findings of this study have implications for treatment of elderly persons with dysphagia using tongue exercise programs. Specifically, increases in tongue force that occur following 8 weeks of progressive resistance tongue exercise may be accompanied by alterations in tongue muscle fiber morphology. These changes may provide greater strength and endurance for goal-oriented actions associated with the oropharyngeal swallow and should be investigated in future research.