scholarly journals Common drive to the upper airway muscle genioglossus during inspiratory loading

2015 ◽  
Vol 114 (5) ◽  
pp. 2883-2892 ◽  
Author(s):  
Michael J. Woods ◽  
Christian L. Nicholas ◽  
John G. Semmler ◽  
Julia K. M. Chan ◽  
Amy S. Jordan ◽  
...  
Keyword(s):  
Upper Airway ◽  
Motor Units ◽  
Quadratic Functions ◽  
Emg Activity ◽  
Respiratory Drive ◽  
Activation Effect ◽  
Single Motor Unit ◽  
Common Drive ◽  
Load Discharge ◽  
Inspiratory Load

Common drive is thought to constitute a central mechanism by which the efficiency of a motor neuron pool is increased. This study tested the hypothesis that common drive to the upper airway muscle genioglossus (GG) would increase with increased respiratory drive in response to an inspiratory load. Respiration, GG electromyographic (EMG) activity, single-motor unit activity, and coherence in the 0–5 Hz range between pairs of GG motor units were assessed for the 30 s before an inspiratory load, the first and second 30 s of the load, and the 30 s after the load. Twelve of twenty young, healthy male subjects provided usable data, yielding 77 pairs of motor units: 2 Inspiratory Phasic, 39 Inspiratory Tonic, 15 Expiratory Tonic, and 21 Tonic. Respiratory and GG inspiratory activity significantly increased during the loads and returned to preload levels during the postload periods (all showed significant quadratic functions over load trials, P < 0.05). As hypothesized, common drive increased during the load in inspiratory modulated motor units to a greater extent than in expiratory/tonic motor units (significant load × discharge pattern interaction, P < 0.05). Furthermore, this effect persisted during the postload period. In conclusion, common drive to inspiratory modulated motor units was elevated in response to increased respiratory drive. The postload elevation in common drive was suggestive of a poststimulus activation effect.

Upper airway and diaphragm muscle responses to chemical stimulation and loading

1982 ◽  
Vol 53 (5) ◽  
pp. 1133-1137 ◽  
Author(s):  
G. B. Patrick ◽  
K. P. Strohl ◽  
S. B. Rubin ◽  
M. D. Altose
Keyword(s):  
Upper Airway ◽  
Chemical Stimulation ◽  
Diaphragm Muscle ◽  
Emg Activity ◽  
Respiratory Drive ◽  
Inspiratory Resistance ◽  
Upper Airway Muscles ◽  
Muscle Responses ◽  
Inspiratory Load ◽  
Parallel Fashion

Previous studies suggest that upper airway muscles in humans respond to changes in chemical respiratory drive in a fashion similar to the diaphragm. To test this hypothesis, in nine seated healthy subjects we monitored electromyographic (EMG) activity from the alae nasi (AN), genioglossus (GG), and diaphragm (DI) not only in response to progressive isocapnic hypoxia and hyperoxic hypercapnia but also to hyperoxic hypercapnia with and without an external inspiratory resistance (15 cmH2O X 1(-1) X s). There were linear increases in DI, GG, and AN in response to increasing chemical drive, but the AN in one subject and the GG in another subject did not respond to hypoxia or hypercapnia. In response to an inspiratory load, subjects decreased ventilation (P less than 0.01) and increased AN, GG, and DI EMG activity (P less than 0.05); however, one subject did not show an AN response to either increased chemical drive or ventilatory loading. We conclude that muscles of the upper airway and the diaphragm are generally activated in a parallel fashion as respiration is stimulated by hypoxia, hypercapnia, and increased inspiratory resistance.

EMG Changes in Human Thenar Motor Units With Force Potentiation and Fatigue

2006 ◽  
Vol 95 (3) ◽  
pp. 1518-1526 ◽  
Author(s):  
C. K. Thomas ◽  
R. S. Johansson ◽  
B. Bigland-Ritchie
Keyword(s):  
Motor Unit ◽  
Motor Units ◽  
Emg Activity ◽  
Single Motor Unit ◽  
Tetanic Force ◽  
Twitch Force ◽  
Emg Amplitude ◽  
Before And After ◽  
Induced Changes ◽  
Motor Unit Emg

Few studies have analyzed activity-induced changes in EMG activity in individual human motor units. We studied the changes in human thenar motor unit EMG that accompany the potentiation of twitch force and fatigue of tetanic force. Single motor unit EMG and force were recorded in healthy subjects in response to selective stimulation of their motor axons within the median nerve just above the elbow. Twitches were recorded before and after a series of pulse trains delivered at frequencies that varied between 5 and 100 Hz. This stimulation induced significant increases in EMG amplitude, duration, and area. However, in relative terms, all of these EMG changes were substantially smaller than the potentiation of twitch force. Another 2 min of stimulation (13 pulses at 40 Hz each second) induced additional potentiation of EMG amplitude, duration, and area, but the tetanic force from every unit declined. Thus activity-induced changes in human thenar motor unit EMG do not indicate the alterations in force or vice versa. These data suggest that different processes underlie the changes in EMG and force that occur during human thenar motor unit activity.

Soft palate muscle activity in response to hypoxic hypercapnia

1994 ◽  
Vol 77 (6) ◽  
pp. 2600-2605 ◽  
Author(s):  
T. Van der Touw ◽  
N. O'Neill ◽  
T. Amis ◽  
J. Wheatley ◽  
A. Brancatisano
Keyword(s):  
Soft Palate ◽  
Minute Ventilation ◽  
Upper Airway ◽  
Emg Activity ◽  
Respiratory Drive ◽  
Breathing Control ◽  
Fine Wire ◽  
Time Average ◽  
Reflex Control ◽  
Local Reflex

We studied the effects of increasing respiratory drive on electromyographic (EMG) soft palate muscle (SPM) activity in nine anesthetized tracheostomy-breathing dogs during hypoxic hypercapnia (HH) with a 14% O2–8% CO2–78% N2 inspired gas mixture. Moving time average EMG activity was recorded from palatinus (PAL), levator veli palatini (LP), and tensor veli palatini (TP) muscles (with bipolar fine-wire electrodes) and diaphragm (DIA; with bipolar hook electrodes). During HH, peak inspiratory DIA activity increased from 18.8 +/- 1.3 to 30.1 +/- 2.0 arbitrary units and minute ventilation increased from 6.2 +/- 0.3 to 18.3 +/- 1.8 l/min (both P < 0.001). Phasic inspiratory, expiratory, and/or tonic EMG activity was present in each SPM during room air breathing (control) and increased during HH (P < 0.05), except for phasic inspiratory PAL and phasic expiratory TP activities. Peak inspiratory LP and TP activities increased during HH to 250 and 179% of control, respectively, and peak expiratory activity increased to 187, 235, and 181% of control in PAL, LP, and TP, respectively. These findings demonstrate respiratory-related regulation of SPM activity independent of local reflex control from the upper airway. However, the combined inspiratory and expiratory phasic recruitment of these muscles differs from the inspiratory recruitment of known upper airway dilator muscles.

Upper airway pressure receptors alter expiratory muscle EMG and motor unit firing

1988 ◽  
Vol 65 (1) ◽  
pp. 210-217 ◽  
Author(s):  
E. van Lunteren ◽  
N. S. Cherniack ◽  
T. E. Dick
Keyword(s):  
Motor Unit ◽  
Unit Activity ◽  
Upper Airway ◽  
Motor Units ◽  
Firing Frequency ◽  
Single Motor Unit ◽  
Expiratory Muscle ◽  
Motor Unit Activity ◽  
Motor Unit Firing ◽  
Respiratory Muscle Activity

To examine the effects of upper airway negative pressure (UAW NP) afferents on respiratory muscle activity during expiration (TE), diaphragm electromyograms (EMG) and triangularis sterni EMG and single motor unit activity were recorded from supine anesthetized tracheotomized cats while they breathed 100% O2. The period of TE during which the diaphragm was electrically active (TE-1) and the period of TE during which the diaphragm was quiescent (TE-2) were both increased with continuous UAW NP (P less than 0.001 and P less than 0.05, respectively), as was TE-1 as a percent of TE (P less than 0.001). Continuous UAW NP reduced peak triangularis sterni EMG (P less than 0.001) and delayed its expiratory onset (P less than 0.005) but did not alter its duration of firing. Changes in triangularis sterni EMG were due to a combination of complete cessation of motor unit activity (2 of 17 motor units), a reduction in mean motor unit firing frequency (P less than 0.02), and a delay in the expiratory onset of motor unit activity (P less than 0.001). Qualitatively similar results were obtained when UAW NP was applied during inspiration only. We conclude that 1) UAW NP has reciprocal stimulatory and inhibitory influences on diaphragm and triangularis sterni muscle electrical activity, respectively, during expiration, and 2) the reductions in triangularis sterni EMG are due to both motor unit derecruitment and a slowing of motor unit firing frequency.

Firing Patterns of Human Genioglossus Motor Units During Voluntary Tongue Movement

2007 ◽  
Vol 97 (1) ◽  
pp. 933-936 ◽  
Author(s):  
E. Fiona Bailey ◽  
Amber D. Rice ◽  
Andrew J. Fuglevand
Keyword(s):  
Firing Rate ◽  
Human Subjects ◽  
Upper Airway ◽  
Motor Units ◽  
Healthy Human ◽  
Single Motor Unit ◽  
Airway Patency ◽  
Tongue Muscle ◽  
Human Tongue ◽  
Tongue Movements

The tongue participates in a range of complex oromotor behaviors, including mastication, swallowing, respiration, and speech. Previous electromyographic studies of the human tongue have focused on respiratory-related tongue muscle activities and their role in maintaining upper airway patency. Remarkably, the activities of human hypoglossal motor units have not been studied during the execution of voluntary maneuvers. We recorded single motor unit activity using tungsten microelectrodes in the genioglossus muscle of 10 healthy human subjects performing both slow tongue protrusions and a static holding maneuver. Displacement of the tongue was detected by an isotonic transducer coupled to the lingual surface through a customized lever arm. For protrusion trials, the firing rate at recruitment was 13.1 ± 3 Hz and increased steeply to an average of 24 ± 6 Hz, often with very modest increases in tongue protrusion. For the static holding task, the average firing rate was 16.1 ± 4 Hz, which is surprisingly high relative to limb motor units. The average coefficient of variation of interspike intervals was ∼20% (range, 10–28%). These are the first recordings of their type obtained in human subjects and provide an initial glimpse into the voluntary control of hypoglossal motoneurons during tongue movements presumably instigated by activity in the motor cortex.

scholarly journals Vastus lateralis single motor unit EMG at the same absolute torque production at different knee angles

2009 ◽  
Vol 107 (1) ◽  
pp. 80-89 ◽  
Author(s):  
T. M. Altenburg ◽  
A. de Haan ◽  
P. W. L. Verdijk ◽  
W. van Mechelen ◽  
C. J. de Ruiter
Keyword(s):  
Motor Unit ◽  
Vastus Lateralis ◽  
Motor Units ◽  
Knee Extensors ◽  
Emg Activity ◽  
Single Motor Unit ◽  
Recruitment Threshold ◽  
Single Motor ◽  
Discharge Rates ◽  
Isometric Torque

Single motor unit electromyographic (EMG) activity of the knee extensors was investigated at different knee angles with subjects ( n = 10) exerting the same absolute submaximal isometric torque at each angle. Measurements were made over a 20° range around the optimum angle for torque production (AngleTmax) and, where feasible, over a wider range (50°). Forty-six vastus lateralis (VL) motor units were recorded at 20.7 ± 17.9 %maximum voluntary contraction (%MVC) together with the rectified surface EMG (rsEMG) of the superficial VL muscle. Due to the lower maximal torque capacity at positions more flexed and extended than AngleTmax, single motor unit recruitment thresholds were expected to decrease and discharge rates were expected to increase at angles above and below AngleTmax. Unexpectedly, the recruitment threshold was higher ( P < 0.05) at knee angles 10° more extended (43.7 ± 22.2 N·m) and not different ( P > 0.05) at knee angles 10° more flexed (35.2 ± 17.9 N·m) compared with recruitment threshold at AngleTmax (41.8 ± 21.4 N·m). Also, unexpectedly the discharge rates were similar ( P > 0.05) at the three angles: 11.6 ± 2.2, 11.6 ± 2.1, and 12.3 ± 2.1 Hz. Similar angle independent discharge rates were also found for 12 units ( n = 5; 7.4 ± 5.4 %MVC) studied over the wider (50°) range, while recruitment threshold only decreased at more flexed angles. In conclusion, the similar recruitment threshold and discharge behavior of VL motor units during submaximal isometric torque production suggests that net motor unit activation did not change very much along the ascending limb of the knee-angle torque relationship. Several factors such as length-dependent twitch potentiation, which may contribute to this unexpected aspect of motor control, are discussed.

Nonlinear behaviour of human motoneurons

1995 ◽  
Vol 73 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Louise Smith ◽  
Tao Zhong ◽  
Parveen Bawa
Keyword(s):  
Steady State ◽  
Firing Rate ◽  
Motor Unit ◽  
Human Subjects ◽  
Motor Units ◽  
Rate Of Change ◽  
Emg Activity ◽  
Nonlinear Behaviour ◽  
Single Motor Unit ◽  
Single Motor

When ramp-and-hold currents are injected into a motoneuron of an anesthetized cat, the motoneuron responds with a high initial firing rate (dynamic phase), which then adapts to a lower steady-state firing rate. The firing rates during the dynamic and the steady-state phases are linearly related to the rate of change and the magnitude of the injected current, respectively. In human subjects, where inputs to the motoneurons are not accessible, force parameters are used to describe motoneuron behaviour. Population responses of human motoneurons, measured in terms of gross electromyographic (EMG) activity, increase linearly with the magnitude and the rate of change of force. No study has attempted to examine the question of linearity of single motor units during the dynamic as well as the steady-state phases. The following study recorded single motor unit and EMG activities simultaneously from the flexor carpi radialis muscle in human subjects completing ramp-and-hold force trajectories. Although the results confirmed the linear relationship between EMG activities and the rate and magnitude of the force, a nonlinear activity pattern was observed between the single motor unit firing and the force parameters, suggesting that recruitment must be responsible for the linear behaviour of EMG activity. Comparisons of different background activity levels on the firing patterns of a given motor unit, as well as comparisons of two simultaneously recorded units, further supported nonlinear response patterns of single motor units.Key words: human, motoneurons, motor units, nonlinearity, force trajectory, repetitive firing.

Synchrony between breathing and shivering in three muscles of bantam hens exposed to cold eggs

1993 ◽  
Vol 265 (6) ◽  
pp. R1439-R1446
Author(s):  
O. Toien
Keyword(s):  
Cold Water ◽  
Motor Units ◽  
Respiratory Frequency ◽  
Emg Activity ◽  
Average Intensity ◽  
Respiratory Drive ◽  
Pectoralis Muscle ◽  
Pectoralis Muscles ◽  
The Brain ◽  
Muscle Circulation

Unrestrained, incubating bantam hens (Gallus domesticus) were exposed to cold, water-perfused eggs to induce shivering. Mean rectified electromyogram (EMG activity) was recorded from the iliotibialis, gastrocnemius, and pectoralis muscles, together with breathing and O2 consumption. EMG activity in all three muscles varied in synchrony with breathing, as confirmed by spectral analysis. The highest shivering intensity occurred during end expiration. This synchrony was also present when respiratory frequency was increased by hypercapnic/hypoxic stimuli and tended to improve with increasing respiratory frequency and tidal volume. The absolute modulation of shivering intensity remained relatively constant with increasing average intensity, indicating that breathing-modulated motor units are activated first. In the less active pectoralis muscle, all activity was modulated. Modulation is probably not restricted to one type of muscle fiber because it occurs in both predominantly red hindquarter muscles and the white pectoralis muscle. It is tentatively suggested that respiratory drive-related influence from the brain stem has a synchronizing effect on spinal cord activity. A bursting activity pattern may be more favorable for muscle circulation than a tonic discharge pattern.

Rectification is required to extract oscillatory envelope modulation from surface electromyographic signals

2014 ◽  
Vol 112 (7) ◽  
pp. 1685-1691 ◽  
Author(s):  
Christopher J. Dakin ◽  
Brian H. Dalton ◽  
Billy L. Luu ◽  
Jean-Sébastien Blouin
Keyword(s):  
Motor Unit ◽  
Stimulus Frequency ◽  
Motor Units ◽  
Surface Emg ◽  
Medial Gastrocnemius ◽  
Single Motor Unit ◽  
Single Motor ◽  
Single Motor Units ◽  
Emg Signal ◽  
Envelope Modulation

Rectification of surface electromyographic (EMG) recordings prior to their correlation with other signals is a widely used form of preprocessing. Recently this practice has come into question, elevating the subject of EMG rectification to a topic of much debate. Proponents for rectifying suggest it accentuates the EMG spike timing information, whereas opponents indicate it is unnecessary and its nonlinear distortion of data is potentially destructive. Here we examine the necessity of rectification on the extraction of muscle responses, but for the first time using a known oscillatory input to the muscle in the form of electrical vestibular stimulation. Participants were exposed to sinusoidal vestibular stimuli while surface and intramuscular EMG were recorded from the left medial gastrocnemius. We compared the unrectified and rectified surface EMG to single motor units to determine which method best identified stimulus-EMG coherence and phase at the single-motor unit level. Surface EMG modulation at the stimulus frequency was obvious in the unrectified surface EMG. However, this modulation was not identified by the fast Fourier transform, and therefore stimulus coherence with the unrectified EMG signal failed to capture this covariance. Both the rectified surface EMG and single motor units displayed significant coherence over the entire stimulus bandwidth (1–20 Hz). Furthermore, the stimulus-phase relationship for the rectified EMG and motor units shared a moderate correlation ( r = 0.56). These data indicate that rectification of surface EMG is a necessary step to extract EMG envelope modulation due to motor unit entrainment to a known stimulus.

scholarly journals Reorganization of multidigit physiological tremors after repetitive contractions of a single finger

2009 ◽  
Vol 106 (3) ◽  
pp. 966-974 ◽  
Author(s):  
Ing-Shiou Hwang ◽  
Zong-Ru Yang ◽  
Chien-Ting Huang ◽  
Mei-Chun Guo
Keyword(s):  
Principal Component ◽  
Motor Units ◽  
Middle Finger ◽  
Neuromuscular Function ◽  
Transfer Effect ◽  
Position Tracking ◽  
Single Finger ◽  
Common Drive ◽  
Middle Ring ◽  
Flexor Digitorum

In light of the interplay among physiological finger tremors, this study was undertaken to investigate the transfer effect of fatigue on coordinative strategies of multiple fingers. Fourteen volunteers performed prolonged position tracking with a loaded middle finger while measures of neuromuscular function, including electromyographic activities of the extensor digitorum (ED)/flexor digitorum superficialis (FDS) and physiological tremors of the index, middle, ring, and little fingers, were monitored. The subjects exhibited inferior tracking congruence and an increase in ED activity at the end of the tracking. Fatigue spread was manifested in a remarkable increase in tremor across fingers, in association with enhanced involuntary tremor coupling among fingers that was topologically organized in relation to the distance of the digits from the middle finger. Principal component analysis suggested that an enhanced 8- to 12-Hz central rhythm contributed primarily to the tremor restructure following fatigue spread. The observed tremor reorganization validated the hypothesis that the effect of fatigue was not limited to the instructed finger and that fatigue functionally decreased independence of the digits. The spreading of fatigue weakens neural inputs that diverge to motor units acting on various digits because of fatigue-related enhancement of common drive at the supraspinal level.

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