The effects of orofacial sensory input on spontaneously occurring and apomorphine-induced rhythmical jaw movements in the anesthetized guinea pig

doi:10.1016/0304-3940(85)90095-3

Neuroscience Letters

Volume 53, Issue 1, 7 January 1985, Pages 45-49

https://doi.org/10.1016/0304-3940(85)90095-3 Get rights and content

Abstract

The effects of tonic mandibular loading (jaw depression) on spontaneously occurring and apomorphine (APO)-induced rhythmical jaw movements (RJMs) were examined in the anesthetized guinea pig. It was found that this type of perturbation significantly increased only the amplitude and burst duration of the masseter (jaw closer) EMG activity, whereas the frequency of RJMs was not changed. The data suggest that jaw closer muscle spindle or temporomandibular joint feedback does not strongly influence the activity of the neural networks responsible for determining the frequency of RJMs in the anesthetized guinea pig.

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Cited by (18)

Relationships between masticatory rhythmicity, body mass and cephalometrically-determined aesthetic and functional variables during development in humans
2014, Archives of Oral Biology
Citation Excerpt :
However, evidence from several sources indicates that the neuromotor mechanisms that would seem most likely to be able to adjust TC to scale with MB in fact do not operate in a way that would allow the scaling to emerge. For instance, ketamine-anesthetized guinea pigs manifest spontaneous rhythmic jaw movements that occur near the natural rate at which the species masticates; however, loading the jaws of these animals with 50-g weights did not affect the frequency of the jaw movements.20 It was posited that spindle-mediated feedback served to increase muscle recruitment sufficient to counter the increased load so that jaw rhythmicity was unaffected.
We studied the relationship between chewing rhythmicity, craniomandibular morphology, and age in humans.
Sixty subjects (10 M:10F/group × three age groups, viz., 4–8, 10–14, and 17–21 years) participated. Subjects chewed gum for 2 min while jaw movements in the frontal plane were videorecorded. Mean and variation in mean chewing cycle duration (T_C) were quantified using maximum opening to maximum opening as cycle boundaries. Five “aesthetic” cephalometric variables (e.g., ANB) and seven “functional” variables (e.g., jaw length) were quantified from subjects’ lateral cephalographs. Simple linear regression models and several multivariate analyses were used in comparisons.
Mean T_C increased and variation in T_C decreased significantly with age. Body mass correlated with age, height, T_C, all seven “functional” variables and only two “aesthetic” variables. Mean T_C was correlated significantly with jaw length, distance from condylion to first molar point, distance from gonion to zygomatic arch, and distance from hyoid to menton.
T_C appeared to adapt with age. Although T_C scaled most significantly with age, it is more likely that T_C is mechanistically linked to jaw length or size. The decrease in T_C variation with age suggests improved efficiency. T_C did not scale with “aesthetic” variables, suggesting that these do not impact chewing rate; however, clinical procedures that impact jaw length may. The negative allometric scaling of T_C with “functional” variables may reflect the pedomorphic jaw and face of humans. Further human studies will provide insights into the nature of scaling and adaptation of rhythmic chewing during development.
Relationship between masticatory rhythm, body mass and mandibular morphology in primates
2013, Archives of Oral Biology
Citation Excerpt :
The central pattern generator receives inputs from sensory receptors in the lips, oral mucosa, jaw-closing muscles and periodontal ligaments around the roots of the teeth, and the final motor commands are sent by the central pattern generator.4,6 Although the duration of a complete mastication sequence, and the parameters of the individual masticatory cycles, vary with food type, the masticatory rhythm produced by the central pattern generator is fixed within individual animals7 and within species.8–12 It has been found that the masticatory frequency decreases as Mb increases.13–19
It has been proposed that rhythmic movements such as locomotion and respiration have a period proportional to body mass^1/4. Mastication basically consists of rhythmic alternation of jaw-closing and jaw-opening movements. We studied the relation between masticatory rhythm and body mass in primates, and masticatory rhythm and mandible morphology.
We measured the chewing cycle duration (CCD), mandibular length, mandible height, mandible width and distance from the condylar process of mandible to the centre of gravity of the mandible. Body mass was quoted from the literature.
The CCD is related to mandible morphology and was found to be proportional to body mass^1/6.
These findings suggest that masticatory rhythm is correlated with body mass and mandibular morphology, and that scaling rate of masticatory rhythm to body mass is slower than for the other rhythms.
Analysis of temporal variation in human masticatory cycles during gum chewing
2013, Archives of Oral Biology
Citation Excerpt :
The neural control of masticatory movements appears to be partly controlled by central pattern generating (CPG) circuits located in the pontine and upper medullary brain stem. The basic movement patterns produced by the CPG are modifiable by sensory feedback and feed forward control during ongoing rhythmic movement sequences.6,7 The sensory modulation either accesses CPG circuits directly via afferent connections with brainstem circuitry, or indirectly via loops involving cerebral regions.7–10
The study investigated modulation of fast and slow opening (FO, SO) and closing (FC, SC) chewing cycle phases using gum-chewing sequences in humans.
Twenty-two healthy adult subjects participated by chewing gum for at least 20 s on the right side and at least 20 s on the left side while jaw movements were tracked with a 3D motion analysis system. Jaw movement data were digitized, and chewing cycle phases were identified and analysed for all chewing cycles in a complete sequence.
All four chewing cycle phase durations were more variant than total cycle durations, a result found in other non-human primates. Significant negative correlations existed between the opening phases, SO and FO, and between the closing phases, SC and FC; however, there was less consistency in terms of which phases were negatively correlated both between subjects, and between chewing sides within subjects, compared with results reported in other species.
The coordination of intra-cycle phases appears to be flexible and to follow complex rules during gum-chewing in humans. Alternatively, the observed intra-cycle phase relationships could simply reflect: (1) variation in jaw kinematics due to variation in how gum was handled by the tongue on a chew-by-chew basis in our experimental design or (2) by variation due to data sampling noise and/or how phases were defined and identified.
Licking rate adaptations to increased mandibular weight in the adult rat
2004, Physiology and Behavior
In this experiment, chronic mandibular loading was used to study adaptation in licking rate. Twenty-four 115-day-old rats were randomly divided into two groups. The experimental group received 1.791±0.083 g submandibular gold implants, and the control group received 0.179±0.009 g submandibular acrylic implants. The animals were videotaped while lapping on two separate occasions preoperatively, and once every week postoperatively for 12 weeks. The videotapes were used to obtain licking rates for each animal at each taping session. The findings showed that licking rate decreased significantly after surgery for both groups; however, the decrease was similar for both the experimental and control groups. This indicates that licking rate was affected by the experimental design, but not specifically by the weight of the gold implant.
Generation of masticatory rhythm in the brainstem
1995, Neuroscience Research
Mastication is a typical rhythmical behavior in mammals. Like respiration, it is now generally accepted that the motor command for the basic pattern of rhythmical oral-facial movements is generated by a neuronal population in the brainstem (central pattern generator, CPG). The central pattern generation of rhythmical masticatory movements can be divided into three processes: (1) generation of the masticatory rhythm, (2) generation of a pattern of activities of the jaw, tongue and facial muscles, and (3) coordination of the activities of these muscles. There are several lines of evidence that the masticatory CPG is functionally subdivided into two neuronal groups: one for generation of the masticatory rhythm, giving the timing signal for rhythmical alternation of jaw closing and jaw opening (central rhythm generator, CRG), and the other for generation of the spatiotemporal pattern of activities of the jaw, tongue and facial muscles. This review will deal, first of all, with the localization of the CRG for rhythmical masticatory jaw movements, sources for its activation, and the premotor neurons mediating its output to the trigeminal motoneurons. Next, we will discuss the neurochemical basis for rhythmical trigeminal motoneuron activity as well as central masticatory rhythm generation. Finally, our recent attempt at induction of neural activities reflecting sucking movements (fictive sucking) in an in vitro preparation is presented.
Diverse firing properties of single motor units in the inner and outer portions of the guinea pig anterior digastric muscle
1993, Archives of Oral Biology
Microwire recordings from the histochemically heterogeneous inner compartment of the guinea pig anterior digastric muscle (ADG) revealed tonic firing of single motor units, which were spontaneously active and could also be recruited following orofacial afferent stimulation and during rhythmic jaw movements (RJM). As units with tonic firing were not observed in the homogeneously fast-twitch outer ADG, the tonic units were classified as slow-twitch motor units. Irregular patterns of motor-unit firing at variable frequencies were observed after orofacial stimulation and during RJM in the outer and inner compartments. The irregular firing pattern of units in the fast-twitch outer compartment was characterized by shorter and less variable bursts than that of units in the heterogeneous inner compartment. A phasic, centrally driven firing pattern was observed during RJM in outer and inner ADG units. The firing frequency of some of these units was modulated during the rhythmical bursts. It is suggested that, as in limb muscles, functionally specialized ADG motor units are recruited in an orderly sequence, starting with spontaneously active, slow-twitch units in the inner compartment, continuing with fast-twitch units recruited upon enhancement of the synaptic drive (as in the case of orofacial stimulation), and ending with massive, rhythmical recruitment of slow- and fast-twitch units during RJM.

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The effects of orofacial sensory input on spontaneously occurring and apomorphine-induced rhythmical jaw movements in the anesthetized guinea pig

Abstract

Arch. Oral Biol.

Arch. Oral Biol.

Neuroscience

Brain Res.

Arch. Oral Biol.

Arch. Oral Biol.

Physiologie nerveuse de la mastication chez le chat et le lapin

Arch. Int. Physiol.

Intracellular analysis of synaptic mechanisms controlling spontaneous and cortically induced rhythmical jaw movements in the guinea pig

J. Neurophysiol.

Biostatistics: A Foundation for Analysis in the Health Sciences