Quality of life in families of Croatian veterans 15 years after the war

Exposure to war trauma with its consequences such as post traumatic stress disorder (PTSD) and disability due to combat injuries poses a significant problem for modern Croatian society. However, this is also a public health problem requiring continuous study of effective treatment strategies to achieve an increase in quality of life of most war-affected groups. Aim of this study was to examine the quality of life of population most affected by war - families of Croatian veterans. Present study included 126 female participants, who agreed to complete physical and psychiatric examination organized by the Ministry of Family, War Veterans and Intergenerational Solidarity. Included were participants with status of either wife of war veteran suffering from PTSD, wife who lost her husband in war circumstances or wife of war veteran with physical disabilities resulting from war activities. All three groups were asked to fill out the World Health Organization Quality of Life Questionnaire - short form (WHOQOL-BREF). Results indicate that assumed intensity of secondary trauma is not associated with quality of life. Namely, the highest level of satisfaction was found in wives of the most seriously affected invalids of war (M=3.77; sd=0.741), folowed by the wives of deceased soldiers (M=3.5; sd= 0.697), while the lowest quality of life results were found in wives of veterans suffering from PTSD (M=3.12; sd=0.608). Our results confirm that, nearly 15 years after the war, wives of disabled or killed Croatian soldiers have a (comparatively) satisfactory quality of their everyday lives, compared to the wives of veterans suffering from PTSD.     

Social support and posttraumatic stress disorder in combat veterans in Croatia

Recent studies have shown that greater social support after combat stress is associated with better psychological posttraumatic outcomes. By comparison of a group of veterans (n = 71) who sought psychiatric help and were diagnosed with PTSD (clinical group) and a group of veterans (n = 43) without PTSD (control group) we examined various components of structural and functional social support in war veterans in Croatia. The measures of social support were assessed for two time periods: a) immediately after the war, and b) at the present time. Results of two-way analysis of variance indicate that veterans without PTSD tend to report significantly higher number of persons who provide them different forms of social support than veterans with PTSD. Perceived family and friends support is higher in veterans without PTSD than in veterans with PTSD. Support received from friends and fellow soldiers decreases over time in both groups, whereas for the clinical group support of friends decreases significantly more.     

The activity of jaw elevator muscles during peanut chewing in patients with temporomandibular joint and muscle pain dysfunction syndrome

A synchronized system of EMG and jaw motion tracking device was used to observe some chewing parameters of jaw elevator muscles in 15 patients with temporomandibular joint and muscle pain dysfunction syndrome (TMJ) and 15 normal subjects. Duration of tooth contact (DTC), duration of muscle contraction before tooth contact (DMC), total duration of muscle contraction (DTM) and velocity of jaw movement during peanut chewing were observed. Symptoms of the TMJ patients included pain and tenderness at joints and muscles, and limitation and clicking at joints during jaw movements. It was found that the TMJ patients needed more numerous breaking off strokes before trituration at the occlusal level. There was a longer DMC in the earlier trituration period and TMJ patients had longer DMC than in normals. No difference was found between right and left side chewing or between temporalis and masseter muscles. DTM in the TMJ group was only slightly longer than in normals and the difference between early and late chewing periods was statistically not significant. DTC was only slightly shorter in the TMJ group while the difference between early and late chewing periods in both groups was significant. The average and maximum closing velocities were significantly lower in the TMJ group in both right and left chewing. The difference in the opening phase was not as significant. It was concluded that DMC and jaw closing velocity are more sensitive parameters than DTM and DTC on the diagnosis of TMJ dysfunction with or without occlusal interference. DTM and DTC are parameters more closely related to the influence of occlusal factors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Three-dimensional temporomandibular joint muscle attachment morphometry and its impacts on musculoskeletal modeling

In musculoskeletal models of the human temporomandibular joint (TMJ), muscles are typically represented by force vectors that connect approximate muscle origin and insertion centroids (centroid-to-centroid force vectors). This simplification assumes equivalent moment arms and muscle lengths for all fibers within a muscle even with complex geometry and may result in inaccurate estimations of muscle force and joint loading. The objectives of this study were to quantify the three-dimensional (3D) human TMJ muscle attachment morphometry and examine its impact on TMJ mechanics. 3D muscle attachment surfaces of temporalis, masseter, lateral pterygoid, and medial pterygoid muscles of human cadaveric heads were generated by co-registering measured attachment boundaries with underlying skull models created from cone-beam computerized tomography (CBCT) images. A bounding box technique was used to quantify 3D muscle attachment size, shape, location, and orientation. Musculoskeletal models of the mandible were then developed and validated to assess the impact of 3D muscle attachment morphometry on joint loading during jaw maximal open-close. The 3D morphometry revealed that muscle lengths and moment arms of temporalis and masseter muscles varied substantially among muscle fibers. The values calculated from the centroid-to-centroid model were significantly different from those calculated using the ‘Distributed model’, which considered crucial 3D muscle attachment morphometry. Consequently, joint loading was underestimated by more than 50% in the centroid-to-centroid model. Therefore, it is necessary to consider 3D muscle attachment morphometry, especially for muscles with broad attachments, in TMJ musculoskeletal models to precisely quantify the joint mechanical environment critical for understanding TMJ function and mechanobiology.     

Immediate effects of the serotonin antagonist granisetron on temporomandibular joint pain in patients with systemic inflammatory disorders

The aim of this study was to investigate if the 5-HT3 antagonist granisetron reduces temporomandibular joint (TMJ) pain in patients with systemic inflammatory joint disorders. Sixteen patients with systemic inflammatory joint disease with pain localized over the TMJ region and tenderness to digital palpation of the TMJ were included. The current resting pain (VASRest) and the pain during maximum mouth opening (VAS(MVM)) of the TMJs were assessed with a 100 mm visual analogue scale. An electronic pressure algometer was used to estimate the pressure pain threshold (PPT) over the lateral aspect of the TMJ. Venous blood was collected for measurement of the plasma and serum levels of 5-HT, erythrocyte sedimentation rate, rheumatoid factor and C-reactive protein. The selective 5-HT3 receptor antagonist granisetron or saline were injected into the posterior part of the upper TMJ compartment in a randomized double-blind manner. The patients in the granisetron group had lower VASRest than the patients in the saline group after 10 min. In the granisetron group, VASRest was decreased after 10 min, while VAS(MVM) was decreased and PPT increased after 20 min. In the saline group, VAS(MVM) was decreased after 20 min. In conclusion, granisetron has an immediate, short-lasting and specific pain reducing effect in TMJ inflammatory arthritis. The 5-HT3 receptor may therefore be involved in the mediation of TMJ pain in systemic inflammatory joint disorders.     

Effect of hyperactivity of the lateral pterygoid muscle on the temporomandibular joint disk

In this study, the effect of hyperactivity of the lateral pterygoid muscle (LPM) on the temporomandibular joint (TMJ) disk during prolonged clenching was examined with a mathematical model. Finite element models of the TMJ were constructed based on magnetic resonance images from two subjects with or without internal derangement of the TMJ. For each model, muscle forces were used as a loading condition for stress analysis for 10 min clenching. Furthermore, an intermittent increase of the LPM force with intervals of 1 min was applied. In the asymptomatic model, large stresses were found in the central and lateral part of the disk at the onset of clenching. In the retrodiscal tissue, stress relaxation occurred during the first 2 min of clenching. When the force of the LPM increased temporarily, the disk moved anteriorly and returned to its original position afterward. In the symptomatic model, large stresses were observed in both the posterior region of the disk and the retrodiscal tissue throughout clenching. Upon temporary increase of the LPM force, the disk was elongated anteriorly, which appeared to be irreversible. These results indicate that hyperactivity of the LPM may be involved in the progression of disk displacement.     

Macaque Pterygoid Muscles: Internal Architecture, Fiber length, and Cross-Sectional Area

Models of mastication require knowledge of fiber lengths and physiological cross-sectional area (PCS), a proxy for muscle force. I dissected 36 medial pterygoid and 36 lateral pterygoid muscles from 30 adult females of 3 macaque species (Macaca fascicularis, M. mulatta, M. nemestrina) using gross and chemical techniques and calculated PCS. These macaques have mechanically similar dietary niches and exhibit no significant difference in muscle architecture or fiber length. Fiber length does not scale with body size (mass) for either total pterygoid muscle or for medial pterygoid muscle mass. However, fiber length scales weakly with lateral pterygoid muscle mass. In each case, differences in PCS among species result from differences in muscle mass not fiber length. Medial pterygoid PCS scales isometrically with body size; larger animals have greater force production capabilities. Medial and lateral pterygoid PCS scale positively allometrically with facial size; individuals with more prognathic faces and taller mandibular corpora have greater PCS, and hence force, values. This positive allometry counters the less efficient positioning of masticatory muscles in longer-faced macaques. PCS is only weakly correlated with bone proxies previously used to estimate muscle force. Thus, predictions of muscle force from bone parameters will entail large margins of error and should be used with caution.     

A quality of life in chronic combat related posttraumatic stress disorder--a study on Croatian War veterans

The main objective of this study was to examine an association of various symptoms in chronic combat-related post traumatic stress disorder (PTSD) and the quality of life in this population. 248 Croatian male war veterans all diagnosed with chronic PTSD were consecutively enrolled in this study as they showed up at the routine check-up. They were given self report questionnaires Trauma Symptom Inventory (TSI-A) evaluating different PTSD symptoms and WHO Quality of Life-BREF assessing four different domains of the quality of life. After independent sample t- test was performed, the presence of each symptom defined by Trauma Symptom Inventory indicated the impairment of all four quality of life domains in a group of subject suffering from it, except of intrusive experience not being associated with the lesser quality in social domain. All quality of life domains were significantly correlated with various PTSD symptoms; however Pearson correlation factors ranged from small to medium value. As expected, PTSD symptoms are associated with lesser quality of life in the affected population. The further research is needed to show possible causal relationship between PTSD and, especially, physical health of these patients.     

Correlation of sleep disturbances, anxiety and depression in Croatian war veterans with posttraumatic stress disorder

The aim of the study was to examine the relationships between global sleep quality and its specific components and Posttraumatic Stress Disorder (PTSD) symptom severity questionnaire. We also researched whether sleep quality and sleep disturbances differed among groups of PTSD based on symptom severity categories. This study was conducted on the sample of 120 Croatian war veterans with PTSD. The following self-report instruments were used: Pittsburgh Sleep Quality Index, the Pittsburgh Sleep Quality Index Addendum for PTSD, the Mississippi Scale for Combat-Related PTSD, the Spielberger State and Trait Anxiety Inventory and the Beck Depression Inventory. There were statistically significant differences between the three PTSD severity groups on general nervousness (PSQI-A variable), where patients with extremely severe PTSD have more symptoms of general nervousness than groups with severe or moderate PTSD. Differences were found between PTSD severity groups in episodes of terror and acting-out dreams, where patients with extremely severe PTSD have more symptoms of episodes of terror and acting-out dreams than groups with severe or moderate PTSD. Sleep quality was significantly correlated with state anxiety, trait anxiety, and depression, indicating that with decrease of anxiety and depression, sleep quality improves. Sleep latency was positively correlated with both state and trait anxiety. There wasn't any significant correlation between sleep latency and depression. Study suggests that sleep disturbances are equally severe across groups of veterans based on PTSD severity and that the severity of sleep disturbances is significantly related to severity of anxiety and depression symptoms.     

Influence of occlusal stabilization splint on the asymmetric activity of masticatory muscles in patients with temporomandibular dysfunction

The aim of present study was to evaluate the symmetry of masticatory muscles' activity at various clenching levels in the intercuspal position in patients with functional disorders and in healthy subjects. The purpose was also to determine the effect of full-arch maxillary stabilization splint on the asymmetry of masticatory muscle activity in patients with temporomandibular dysfunction. In this study 6 TMD patients and 12 healthy subjects were investigated. Surface EMG recordings were obtained from left and right anterior temporal, left and right masseter and from the sub-mandibular group in the region of the anterior belly of the digastric muscle on the left and right side during clenching with the maximum 100% voluntary contraction (MVC) as well as during clenching at 50% and 25% of the maximum activity in the position of maximal intercuspation of teeth. In order to quantify asymmetrical masticatory muscle activity, the asymmetry index (AI) was calculated for each subject and for each muscle from the average anterior temporal, masseter and digastric potentials recorded during each test (100% MVC, 50% MVC and 25% MVC). In the group of patients EMG recordings were repeated during and after the splint therapy. The asymmetries of masticatory muscle activity was present in both groups, but in the group of TMD patients the asymmetry indices for anterior temporal muscle at 100% MVC (p = 0.049) and 50% MVC (p = 0.031) were significantly higher. Results have shown that the use of splint suppressed the asymmetry of all muscles, as during the splint therapy the asymmetry indices were lowered. After the therapy, the level of temporal muscle symmetry during submaximal clenching in the intercuspal position increased significantly (p = 0.046). This investigation points out that electromyography may be a valuable method of documenting that asymmetric activity of masticatory muscles improves after occlusal splint therapy in patients with TMD.     

Dental Implants – Perceiving Patients’ Satisfaction in Relation to Clinical and Electromyography Study on Implant Patients

The aim of this study is to evaluate the satisfaction of patients with posterior implants in relation to the clinical success criteria and surface electromyography (sEMG) findings of the masseter and temporalis muscles. Total 42 subjects were investigated. Twenty one subjects with posterior dental implants were interviewed using a questionnaire and the clinical success criteria were determined based on The International Congress of Oral Implantologists. The myofunction of the masticatory muscles were assessed using sEMG (21 subjects) and compared to the control group of subjects without implants (21 subjects). Out of 21 subjects, all were satisfied with the aesthetics of their implant. Twenty of them (95.2%) were satisfied with its function and stability. As for clinical criteria, 100% (50) of the implants were successful with no pain, mobility or exudates. sEMG findings showed that patients have significantly lower (p<0.01) basal or resting median power frequency but with muscle burst. During chewing, control subjects showed faster chewing action. There was no difference in reaction and recovery time of clenching for both groups. In conclusion, the satisfaction of implant patients was high, and which was in relation to the successful clinical success criteria and sEMG findings.     

Masticatory muscles of domestic sheep and swine in ontogenesis

Age changes of morphometrical parameters of the masticatory muscles have been analyzed in domestic sheep and pigs of white large breed in the following age groups: 2-, 3-, 4-month-old fetuses, newborns, 4-month-old lambs, 10-month-old pigs, 18-month-old lambs, mature she-sheep and brood-sows. Uneven weight growth of the masticatory muscles in the sheep and pigs during the prenatal ontogenesis should be considered as a consequence of recapitulation of their phylogenesis, and in the postnatal ontogenesis it depends on changes in life conditions, type of nutrition, character of food and type of life. In newborn sheep the digastric, lateral, pterygoid and temporal muscles grow intensively, and in pigs--medial pterygoid and temporal ones. When they pass to roughage, in the former the mass of the musculus masseter major and medial pterygoid muscle increases, and in the latter--that of the musculus masseter major and temporal one. The masticatory muscles of the species studied increase in their mass especially intensively during the middle of the prenatal ontogenesis and during suckling period of their development. This should be taken into consideration in stock-breeding practice. In domestic pigs there is only one muscular belly in the digastric muscle. In sheep there are two bellies, separated one from another by means of a tendinous intersection, owing to crossing of the latter by the stylohyoid muscle.     

Measurement of mandibular movements in patients with temporomandibular disorders and in asymptomatic subjects

The aim of the study was to investigate the range of mandibular movements and to analyze the difference in range of mouth opening, right and left lateral movements, and protrusive movement between patients with clinical diagnoses of temporomandibular disorders and asymptomatic subjects (control group) in a young male population. A total of 240 subjects, aged 19-28, were included in the study. The TMD sample comprised 180 patients (60 patients with muscle disorders; 60 patients with disc displacement with reduction; and 60 patients with muscle disorders and disc displacement with reduction) and was compared with 60 healthy control subjects. All participants were evaluated by the attending dentists at baseline by means of a physical examination of the masticatory system and a history questionnaire which included the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I measures. Analysis of variance (ANOVA) with the post hoc Bonferroni criteria showed significant difference in ranges of mandibular movements between and within the groups of asymptomatic subjects and TMD patients for active mouth opening (p = 0.001), right lateral movement (p = 0.002), left lateral movement (p = 0.006), and protrusive movement (p = 0.05). It has been found that there are statistically significant differences in the range of mandibular movements that separate asymptomatic subjects and patients with muscle disorders and disc displacements with reduction in this young male population. However, we cannot conclude that measurements of active mandibular movements can discriminate one group (TMD patients) from the other (asymptomatic subjects), because the mean ranges of these active movements between the groups were measured in clinically "normal" values.     

Adaptations in the gait pattern with experimental hamstring pain

Pain changes movement but most studies have focused on basic physiological adaptations during non-functional movement tasks. The existing studies on how pain affects lower extremity gross movement biomechanics have primarily involved movements in which the quadriceps is the primary muscle and little attention has been given to how pain in other muscles affects functional movement. The purpose of this study was to investigate the changes in the gait patterns of healthy subjects that occur during experimental muscle pain in the biceps femoris.In a cross-over study design, 14 healthy volunteers underwent EMG assisted 3D gait analyses before, during and after experimental biceps femoris pain induced by intramuscular injections of hypertonic saline. Isotonic saline injections were administered as a non-painful control.The experimental biceps femoris pain led to reductions in hip extensor moments, knee flexor and lateral rotator moments. No changes in lower extremity kinematics and EMG activity in any of the recorded muscles were observed.It is concluded that experimental muscle pain in the biceps femoris leads to changes in the gait pattern in agreement with unloading of the painful muscle. The changes are specific to the painful muscle. The present study provides support to the theory that musculoskeletal pain is a protective signal leading to changes in movement patterns that serve to unload the painful tissue.     

Jaw muscles in older overdenture patients

Objective: To determine, using computer tomography (CT), whether the retention of a small number of teeth in the older adult used to support overdentures could affect the cross‐sectional area (CSA) and X‐ray density of two jaw closing muscles. Design: Cross‐sectional study of a group of older patients subdivided into dentate, edentulous and those wearing overdentures supported by two to five teeth. Subjects: The sample consisted of 24 subjects aged 55–68 years. Outcome measures: CSA and X‐ray density of two jaw closing muscles, masseter and medial pterygoid were measured and evaluated using CT. Results: There were no significant differences between left and right jaw muscles, but the CSA of the masseter muscles were significantly larger than the medial pterygoid muscles. The CSA of the masseter and medial pterygoid muscles was significantly smaller in edentulous subjects compared with dentate subjects but no significant difference was observed between subjects wearing overdentures and those with a natural dentition. No significant differences were observed with the X‐ray density between different muscles or dental states. Conclusion: The retention of a small number of teeth in the older adult used to support overdentures appears to sustain the CSA of two jaw closing muscles and therefore could enhance these patients’ masticatory ability compared with those who were edentulous.     

A bilateral maxillofacial trunk in man: an extraordinary anomaly of the carotid system of arteries.

In a Caucasian male, the maxillary artery (M) bilaterally arose with the facial artery anteromedially from the external carotid artery. On the right side, the M entered the infratemporal fossa between the neck of the mandible and the medial pterygoid muscle, whereas the left M pierced the medial pterygoid muscle, first being covered by the muscle and the angle of the mandible. On both sides, the M ran deep to the inferior head of the lateral pterygoid muscle and the buccal nerve. The right M lay deep to the inferior alveolar, but superficial to the lingual nerve, whereas the left inferior alveolar and lingual nerves had formed two roots, thus encircling the left M. The ascending palatine artery was replaced on both sides by palatine branches of the ascending pharyngeal artery. Since a bilaterial maxillofacial trunk with topographical relations as described herein has not been previously reported in man, the embryology and comparative anatomy of this variation are discussed.     

Mechanical advantage of area of origin for the external pterygoid muscle in two murid rodents, Apodemus speciosus and Clethrionomys rufocanus

The actions of masticatory muscles in relation to transverse grinding, associated with forward masticatory movement of the mandible, were investigated by using a mechanical model in the two murid rodents, the Japanese field mouse (Apodemus speciosus: subfamily Murinae) and the gray red-backed vole (Clethrionomys rufocanus: subfamily Arvicolinae). Furthermore, statics of the masticatory system on a sagittal plane while chewing is taking place were also analyzed in these rodents. The inward grinding movements of hemimandibles are generated by the posterior temporalis and internal and external pterygoids in both species. In addition to these muscles, the anterior temporalis also moves the hemimandibles lingually in Apodemus speciosus. The area of origin of the external pterygoid seems more advantageous for transverse grinding in A. speciosus than in Clethrionomys rufocanus. On the basis of the static analysis, the anterodorsal area of origin of the external pterygoid to the upper second and third molars in Clethrionomys rufocanus appears to be an adaptive character to prevent the jaw joints from dislocation during occlusion at a posterior point on the elongated row of cheek teeth.     

Heart Rate Variability (HRV) and Posttraumatic Stress Disorder (PTSD): A Pilot Study

Exposure to combat experiences is associated with increased risk of developing Post Traumatic Stress Disorder. Prolonged exposure therapy and cognitive processing therapy have garnered a significant amount of empirical support for PTSD treatment; however, they are not universally effective with some patients continuing to struggle with residual PTSD symptoms. Heart rate variability (HRV) is a measure of the autonomic nervous system functioning and reflects an individual’s ability to adaptively cope with stress. A pilot study was undertaken to determine if veterans with PTSD (as measured by the Clinician-Administered PTSD Scale and the PTSD Checklist) would show significantly different HRV prior to an intervention at baseline compared to controls; specifically, to determine whether the HRV among veterans with PTSD is more depressed than that among veterans without PTSD. The study also aimed at assessing the feasibility, acceptability, and potential efficacy of providing HRV biofeedback as a treatment for PTSD. The findings suggest that implementing an HRV biofeedback as a treatment for PTSD is effective, feasible, and acceptable for veterans. Veterans with combat-related PTSD displayed significantly depressed HRV as compared to subjects without PTSD. When the veterans with PTSD were randomly assigned to receive either HRV biofeedback plus treatment as usual (TAU) or just TAU, the results indicated that HRV biofeedback significantly increased the HRV while reducing symptoms of PTSD. However, the TAU had no significant effect on either HRV or symptom reduction. A larger randomized control trial to validate these findings appears warranted.     

以乳突切迹和翼钩为基点的侧颅底分区方法

目的：探讨以乳突切迹和翼钩为基点的侧颅底分区新方法。方法：在乳突切迹后缘、翼钩、枕骨大孔前缘中点和颧根四个结构间相互连线,区分侧颅底并测量连线的长度。结果：乳突切迹与侧颅底重要结构的关系密切,切迹后缘与翼钩连线和正中线将侧颅底分成内、外侧两个大的三角区,每个区再分成前后两个三角区共四个三角区,即腭和颞下三角、咽三角、关节和听三角、血管神经三角,其中血管神经三角的三边长度左右侧分别为（74.52±5.47）mm和（74.66±5.41）mm、（59.77±3.84）mm和（59.67±3.56）mm、（42.23±3.11）mm和（42.48±2.60）mm。结论：本研究提供了新的侧颅底分区方法,且血管神经三角的区域划分更为科学,为临床侧颅底手术入路和定位提供了解剖学参考。     

The somatotopy of the masticatory neurons in the rat trigeminal motor nucleus as revealed by HRP study

Young adult albino rats of Wistar strain were used for the present study. 0.5 to 15 microliters of 20-50% of horseradish peroxidase (HRP) were injected into each individual muscle of mastication to label neurons in the trigeminal motor nucleus (TMON) for light microscopic study. The results reveal that: (1) Many HRP-labeled, multipolar neurons are observed in the motor nucleus in each jaw-closing muscle (JCM) with less in each the jaw-opening muscle (JOM). (2) The motor neurons innervating each masticatory muscle in the motor nucleus show a somatotopic arrangement: (a) those innervating the temporalis muscle are located in the medial and dorsomedial parts; (b) those innervating the masseter muscle are located in the intermediate and lateral; (c) those innervating the medial and lateral pterygoid muscles are located in the lateral, ventrolateral and ventromedial parts, respectively; and (d) those innervating the mylohyoid and the anterior belly of the digastric muscles are located in the most ventromedial part of the caudal one-third of the nucleus. Axons of most masticatory motor neurons run ventrolaterally in between the motor and the chief sensory nuclei of the trigeminal nerve. However, those of the mylohyoid and anterior belly of the digastric muscles ascend dorsally to the dorsal aspect of the caudal nucleus and then turn ventrolaterally to join the motor root of the trigeminal nerve. Furthermore, the dendrites of the motor neuron of JCM converge dorsocaudally to the supratrigeminal region. The diameters of neurons of each JCM display a bimodal distribution. However, an unimodal distribution is present in the motor neurons from each JCM. It is suggested that the motor nucleus innervating the JCM is comprised of comprised of alpha- and gamma-motor neurons. It, thus, may provide a neural basis for the regulation of the muscle tone and biting force.