Thresholds, Firing Rates, and Order of Recruitment of Anterior Temporalis Muscle Single-Motor Units During Experimental Masseter Muscle Pain

2021 ◽  
Vol 35 (2) ◽  
pp. 93-104
Author(s):  
Polyana Ferreira ◽  
Isbel Sandoval ◽  
Terry Whittle
Keyword(s):  
Muscle Pain ◽  
Masseter Muscle ◽  
Motor Units ◽  
Temporalis Muscle ◽  
Firing Rates ◽  
Single Motor ◽  
Single Motor Units ◽  
Anterior Temporalis

Functional Properties of Single Motor Units in the Inferior Head of Human Lateral Pterygoid Muscle: Task Firing Rates

2002 ◽  
Vol 88 (2) ◽  
pp. 751-760 ◽  
Author(s):  
I. Phanachet ◽  
T. Whittle ◽  
K. Wanigaratne ◽  
G. M. Murray
Keyword(s):  
Firing Rate ◽  
Correlation Coefficients ◽  
Motor Units ◽  
Lateral Pterygoid Muscle ◽  
Jaw Movements ◽  
Firing Rates ◽  
Single Motor ◽  
Single Motor Units ◽  
Fine Control ◽  
Contralateral Movement

The precise function of the inferior head of the human lateral pterygoid muscle (IHLP) is unclear. The aim of this study was to clarify the normal function of the IHLP. The hypothesis was that an important function of the IHLP is the generation and fine control of horizontal (i.e., anteroposterior and mediolateral) jaw movements. The activities of 50 single motor units (SMUs) were recorded from IHLP (14 subjects) during two- or three-step contralateral movement ( n = 36) and/or protrusion ( n = 33). Most recording sites were identified by computer tomography. There was a statistically significant overall increase in firing rate as the magnitude of jaw displacement increased between the holding phases (range of increments: 0.3–1.6 mm). The firing rates during the dynamic phases for each unit were significantly greater than those during the previous holding phases but less than those during the subsequent holding phases. For the contralateral step task at the intermediate rate, the cross-correlation coefficients between jaw displacement in the mediolateral axis and the mean firing rate of each unit ranged from r = 0.29 to 0.77; mean ± SD; r = 0.49 ± 0.13 (protrusive step task: r = 0.12–0.74, r = 0.44 ± 0.14 for correlation with anterior–posterior axis). The correlation coefficients at the fast rate during the contralateral step task and the protrusive step task were significantly higher than those at the slow rate. The firing rate change of the SMUs per unit displacement between holding phases was significantly greater for the lower-threshold than for the higher-threshold units during contralateral movement and protrusion. After dividing IHLP into four regions, the SMUs recorded in the superior part exhibited significantly greater mean firing rate changes per unit displacement during protrusion than for the SMUs recorded in the inferior part. Significantly fewer units were related to the protrusive task in the superior–medial part. These data support previously proposed notions of functional heterogeneity within IHLP. The present findings provide further evidence for an involvement of the IHLP in the generation and fine control of horizontal jaw movements.

Reorganization of Masseter and Temporalis Muscle Single Motor Unit Activity During Experimental Masseter Muscle Pain

2020 ◽  
Vol 34 (1) ◽  
pp. 40-52
Author(s):  
Polyana Ferreira ◽  
Isbel Sandoval ◽  
Terry Whittle ◽  
Yalda Mojaver ◽  
Greg Murray
Keyword(s):  
Motor Unit ◽  
Unit Activity ◽  
Muscle Pain ◽  
Masseter Muscle ◽  
Temporalis Muscle ◽  
Single Motor Unit ◽  
Single Motor ◽  
Motor Unit Activity

Modulation of stretch-evoked reflexes in single motor units in human masseter muscle by experimental pain

2000 ◽  
Vol 132 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Peter Svensson ◽  
Timothy S. Miles ◽  
Thomas Graven-Nielsen ◽  
Lars Arendt-Nielsen
Keyword(s):  
Masseter Muscle ◽  
Experimental Pain ◽  
Motor Units ◽  
Single Motor ◽  
Single Motor Units

Discharge Characteristics of Laryngeal Single Motor Units During Phonation in Young and Older Adults and in Persons With Parkinson Disease

1999 ◽  
Vol 81 (5) ◽  
pp. 2131-2139 ◽  
Author(s):  
Erich S. Luschei ◽  
Lorraine O. Ramig ◽  
Kristin L. Baker ◽  
Marshall E. Smith
Keyword(s):  
Older Adults ◽  
Parkinson Disease ◽  
Skeletal Muscles ◽  
Motor Units ◽  
Discharge Characteristics ◽  
Laryngeal Muscles ◽  
Firing Rates ◽  
Single Motor ◽  
Single Motor Units ◽  
Human Skeletal Muscles

Discharge characteristics of laryngeal single motor units during phonation in young and older adults, and in persons with Parkinson disease. The rate and variability of the firing of single motor units in the laryngeal muscles of young and older nondisordered humans and people with idiopathic Parkinson disease (IPD) were determined during steady phonation and other laryngeal behaviors. Typical firing rates during phonation were ∼24 s/s. The highest rate observed, during a cough, was 50 s/s. Decreases in the rate and increases in the variability of motor unit firing were observed in the thyroarytenoid muscle of older and IPD male subjects but not female subjects. These gender-specific age-related changes may relate to differential effects of aging on the male and female voice characteristics. The range and typical firing rates of laryngeal motor units were similar to those reported for other human skeletal muscles, so we conclude that human laryngeal muscles are probably no faster, in terms of their contraction speed, than other human skeletal muscles. Interspike interval (ISI) variability during steady phonation was quite low, however, with average CV of ∼10%, with a range of 5 to 30%. These values appear to be lower than typical values of the CV of firing reported in three studies of limb muscles of humans. We suggest therefore that low ISI variability is a special although not unique property of laryngeal muscles compared with other muscles of the body. This conceivably could be the result of less synaptic “noise” in the laryngeal motoneurons, perhaps as a result of suppression of local reflex inputs to these motoneurons during phonation.

Activation of Lip Motor Units With Variations in Speech Rate and Phonetic Structure

1995 ◽  
Vol 38 (4) ◽  
pp. 772-782 ◽  
Author(s):  
Michael D. McClean ◽  
John L. Clay
Keyword(s):  
Speech Rate ◽  
Motor Units ◽  
Interspike Intervals ◽  
Single Motor Unit ◽  
Lower Lip ◽  
Firing Rates ◽  
Single Motor ◽  
Single Motor Units ◽  
Lip Movement ◽  
Intraoral Pressure

The purpose of this study was to describe the activation characteristics of lip-muscle single motor units in relation to speech rate and phonetic structure. Repeated experiments were carried out on three adult subjects from whom recordings of lower lip EMG and two-dimensional displacement were obtained. Single motor unit recordings were obtained from the orbicularis oris inferior (OOI), depressor labii inferior (DLI), and mentalis (MENT) muscles. Subjects' tasks involved repeating CV syllables at 1 to 4 syllables per second (syl/sec). The distribution of interspike intervals and corresponding firing rates were obtained on 11 motor units. The firing rates of OOI and MENT motor units increased as syllable rate changed from 1 to 3 syl/sec, but firing rates tended to be equivalent at 3 and 4 syl/sec. DLI and tonic motor units showed little or no modulation in their firing rates with speech rate. Firing rate data and related observations on lip movement and EMG spike count levels suggest that distinct neuromechanical processes control lip movements at low and high speech rates. Both kinematic and EMG data support the expectation that phonetic structure has its greatest effects on lip opening compared to lip closing movements in CV syllables. OOI and MENT activation levels tended to be highest for /p/ productions compared to /w/ and /f/. This may be related to the requirements for complete lip closure and elevated levels of intraoral pressure for production of /p/.

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