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PubMed2004

Coordination of jaw and extrinsic tongue muscle activity during rhythmic jaw movements in anesthetized rabbits.

To clarify the jaw-closer and tongue-retractor muscle activity patterns during mastication, electromyographic activity of the styloglossus (SG) as a tongue-retractor and masseter (Mass) as a jaw-closer muscles as well as jaw-movement trajectories were recorded during cortically evoked rhythmic jaw movements (CRJMs) in anesthetized rabbits. The SG and Mass muscles were mainly active during the jaw-closing (Cl) phase. The SG activity was composed of two bursts in one masticatory cycle; one had its peak during the jaw-opening (Op) phase (SG1 burst) and the other during the Cl phase (SG2 burst). The Mass activity during the Cl phase was dominant on the working side (opposite to the stimulating side) while the SG1 and SG2 bursts were not different between the sides. When the wooden stick was inserted between the molar teeth on the working side during CRJMs, the facilitatory effects on the SG1 and SG2 bursts on both sides were noted as well as those on the Mass bursts, but the effects on the SG1 burst seemed to be weak as compared with those on the Mass and SG2 bursts. The difference in the burst timing between the sides was noted only in the SG1 burst. When the trigeminal nerves were blocked, the peak and area of the SG and Mass burst decreased during CRJMs, and the facilitatory effects of the wooden stick application on the muscles were not noted. The results suggest that the jaw and tongue muscle activities may be adjusted to chew the food and make the food bolus.

Anesthesia↗
PubMedDate not supplied

Effects of attentional strategies and anxiety constraints on perceptual-motor organisation of rhythmical arm movements.

Effects of anxiety on perceptual-motor organisation of rhythmical forearm movements were examined using an interrupted time series design with staggered baselines. Participants were exposed to repeated baseline sessions interrupted with two anxiety-inducing sessions. Results showed that under moderate levels of anxiety, determined from CSAI-2 and heart rate data, phase relations between oscillating forearms became more stable in in-phase (0 degrees ) and anti-phase (180 degrees ) modes, although these patterns were not maintained in baseline sessions following the anxiety manipulation. Data were consistent with participants employing a strategy of allocating greater attentional effort in stabilizing preferred co-ordination patterns under anxiety-inducing conditions. Results suggest that anxiety can temporarily act as a source of behavioural information, leading to the re-parameterisation of participants' intrinsic dynamics.

Activity Cycles↗
PubMed1996

Rhythmical leg movements in low-risk and brain-damaged preterm infants.

The characteristics of rhythmical kicking movements of preterm infants with documented brain damage (BD), who later showed a severe motor impairment, are described and compared with those of low-risk (LR) preterm infants. Spontaneous movements were videotaped for 60 min in the incubator or in a warmer. A first group of 6 BD and 6 LR infants was observed at 31-35 weeks of postmenstrual age (PMA) and a second group (6 BD, 6 LR) at 37-39 weeks. Bouts of rhythmical kicks, defined as leg movements repeated in the same form at least three times at regular short intervals, were analysed during periods of activity. The results indicated non-significant differences between BD and LR infants at 31-35 weeks of PMA. In contrast, some differences were observed at 37-39 weeks. These differences were not due to leg movement frequency, but to inter-leg coordination and to temporal organisation of the kicking cycles. LR infants exhibited more alternate-leg movements and fewer semi-both-leg movements (simultaneous flexion and non-simultaneous extension) than BD infants. In LR cases the duration of the pause between flexion and extension was shorter, whereas flexion and extension periods were similar for all infants. Although there were significant differences, quantitative analysis of kicking characteristics was not clinically useful because of the large overlap in findings between the two groups. On the other hand Gestalt evaluation of general movements of the same videorecordings showed a closer correlation with the presence of brain lesions and with neurological outcome.

Brain Diseases↗
PubMed2000

Motor control testing of upper limb function after botulinum toxin injection: a case study.

OBJECTIVE: To evaluate changes in upper extremity function in a hemiparetic patient after treatment with botulinum toxin (BTX) using motor-control testing (MCT) techniques. DESIGN: Interventional with longitudinal study, open label. SETTING: A children's hospital and a motor-control laboratory at a major academic center. PARTICIPANTS: A 16-year-old male with right hemiparetic cerebral palsy and a healthy 12-year-old control subject. INTERVENTIONS: BTX injections to the elbow and wrist flexors. MAIN OUTCOME MEASURES: MCT was used to examine 4 upper extremity movements: forward reach, bilateral rhythmic movements (both muscle homologous and direction homologous), isometric pinch, and hand tapping. The patient was tested before treatment and at 2, 4, 6, 12, 18, and 24 weeks after treatment. In addition, range of motion (ROM), the Ashworth scale of spasticity, Functional Independence Measure, and the mobility and activities of daily living (ADL) sections of the Pediatric Evaluation of the Disability Inventory were performed. RESULTS: Forward reach demonstrated little change initially despite patient reports of "feeling looser." Improvement was noted after 18 weeks, but returned to baseline level at 24 weeks. Bilateral rhythmic movements also showed slight improvement at 18 weeks. Pinch force increased significantly after 2 weeks, but declined again at 6 weeks. Improvements occurred in ROM and the Ashworth rating of spasticity, but were not temporally associated with each other or with MCT results. Functional assessment data did not change during the study period. CONCLUSIONS: Improvements in more complex motor tasks were noted after significant delay from the time of treatment, while simpler tasks demonstrated a more rapid improvement, followed by a rapid return to baseline levels. This case suggests that MCT techniques can provide quantitative and qualitative data, which can add new information about upper extremity motor disability and the outcome of treatment.

Adolescent↗
PubMed2000

Effect of norepinephrine receptors on trigeminal rhythm generation in newborn rats.

N-methyl-D,L-aspartate acid and bicuculline are required to enhance the trigeminal rhythmic activities in an in vitro isolated brainstem block preparation. In this study, we analyzed the effect of norepinephrine on the trigeminal neural circuit underlying rhythmic jaw movements. Rhythmic trigeminal activity is observed in brainstem preparations (inferior colliculus to obex) only following blockade of alpha(2)-adrenoceptors with idazoxan. This observation, combined with the inhibition of rhythm by alpha(2)-adrenoceptor agonists suggests endogenous alpha(2)-adrenoceptor mediated inhibition of trigeminal networks. A complex noradrenergic modulation of trigeminal systems is further supported by the prazosin-sensitive potentiation of rhythm by bath application of the alpha(1)-adrenoceptor agonist phenylephrine.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1984

Differentiation of the neural pathways mediating cortically induced and dopaminergic activation of the central pattern generator (CPG) for rhythmical jaw movements in the anesthetized guinea pig.

The central pattern generator (CPG) for rhythmical jaw movements (RJMs) was activated, in the anesthetized guinea pig, by systemic injection of a specific dopamine agonist, apomorphine (APO). It was shown that APO induced RJMs required an intact superior colliculus, and were blocked by low doses (0.05-1.0 mg/kg) of haloperidol (HAL), a dopamine antagonist. This is in contrast to the neural pathways mediating RJMs evoked by repetitive electrical stimulation of the masticatory cortex which remained effective following both lesions of the superior colliculus and administration of HAL. These results suggest that there are at least two anatomically separate and pharmacologically distinct command centers for activation of the CPG for RJMs in the guinea pig.

Animals↗
PubMed1990

Two types of rhythmical jaw movements evoked by stimulation of the rat cortex.

Two different patterns of rhythmical jaw movements (RJM) resembling masticatory movements were evoked by stimulation of the cerebral cortex in the rat. The first type of RJM was evoked from the primary jaw motor area, and it always began with a sustained jaw-opening and consisted of high frequency (5-7 Hz) simple opening-closing movements of the jaw. The anterior digastric electromyographic (EMG) activity showed discharges apparently time-locked to each stimulus pulse. The second type of RJM was evoked from the ventral part of the insular cortex. In contrast to the first type of RJM, the second type started with a jaw closing movement in many cases. This type of RJM had large and complex lateral and sagittal movements and the frequency of RJM was low (3-4 Hz). The digastric EMG activity did not show the stimulus-locked component. The pattern of these RJM did not depend on the intensity or frequency of stimulation, but on the site stimulated. These two cortical RJM areas appeared to work independently from each other, because ablation of one area did not affect the pattern of the RJM evoked from the other cortical area.

Animals↗
PubMed2001

Putative feed-forward control of jaw-closing muscle activity during rhythmic jaw movements in the anesthetized rabbit.

When a thin plastic test strip of various hardness is placed between the upper and lower teeth during rhythmical jaw movements induced by electrical stimulation of the cortical masticatory area (CMA) in anesthetized rabbits, electromyographic (EMG) activity of the masseter muscle is facilitated in a hardness-dependent manner. This facilitatory masseteric response (FMR) often occurred prior to contact of the teeth to the strip, and thus preceded the onset of the masticatory force. Since this finding suggests involvement of a feed-forward mechanism in the induction of the FMR, the temporal relationship between the onset of the FMR and that of the masticatory force was analyzed in five sequential masticatory cycles after application of the strip. The FMR was found to precede the onset of masticatory force from the second masticatory cycle after application of the strip, but never did in the first cycle. This finding supports the concept of a feed-forward control mechanism that modulates FMR timing. Furthermore, the FMR preceding the force onset disappeared after making a lesion of the mesencephalic trigeminal nucleus (MesV) where the ganglion cells of the muscle spindle afferents from the jaw-closing muscles are located. In contrast, no such change occurred after blocking periodontal afferents by transection of both the maxillary and the inferior alveolar nerves. The putative feed-forward control of the FMR is therefore dependent mainly on sensory inputs from the muscle spindles, but little on those from the periodontal receptors, if any. We further examined the involvement of the CMA with the putative feed-forward control of the FMR via the transcortical loop. For this purpose, rhythmical jaw movements were induced by stimulation of the pyramidal tract. No significant change in the timing of the FMR occurred after the CMA ablation, which strongly suggests that the CMA is not involved in the putative feed-forward control of the FMR. The FMR was also noted to increase significantly in a hardness-dependent manner even after the MesV lesion, although the rate of increment decreased significantly. Contribution of muscle spindles and periodontal receptors to the hardness-dependent change of the FMR is discussed.

Anesthesia↗
PubMed2006

The relationship between reduplicated babble onset and laterality biases in infant rhythmic arm movements.

This study examined changes in rhythmic arm shaking and laterality biases in infants observed longitudinally at three points: just prior to, at, and just following reduplicated babble onset. Infants (ranging in age from 4 to 9 months at babble onset) were videotaped at home as they played with two visually identical audible and silent rattles presented at midline for 1.5 min each. Rate of rattle shaking increased sharply from the pre-babble to the babble onset session; but there was no indication that this increase was specific to the right arm. This finding suggests that the link between babble onset and increased rhythmic arm activity may not be the product of language-specific mechanisms, but is rather part of a broader developmental process that is also perceptual and motor.

Analysis of Variance↗
PubMed1999

Activity of the rat pontomedullary reticular neurons related to rhythmical jaw movements.

Electrical stimulation of the cerebral peduncle or oral mechanical or chemical stimulation induced rhythmical jaw movements (RJM) in the anesthetized rat. Extracellular recording was made from the pontomedullary reticular neurons in relation to RJM. The RJM-related activity was classified to a tonic, a transient and a phase-dependent rhythmical activities (116, 92 and 45 neurons, respectively). We found that the neurons showing the phase-dependent activities discharged exclusively or almost exclusively during RJM without responding to at least one of three kinds of RJM-inducing stimulation. Fourteen neurons were activated by all kinds of RJM-inducing stimulation and majority of them showed weak or no change in activity during RJM, although some showed the transient or the rhythmical activity during RJM. We propose that the phase-dependent rhythmical activity is necessary to generate RJM since any stimulation-induced RJM was reversibly blocked by microinjection of lidocaine or glutamate receptor blocking agents into the brainstem site concentrated by this type of neurons. No other type of activity was observed exclusively during RJM.

Animals↗
PubMed1997

Regulation of masticatory force during cortically induced rhythmic jaw movements in the anesthetized rabbit.

To examine the relationships between masticatory force, electromyogram (EMG) of masticatory muscles, and jaw movement pattern, we quantitatively evaluated the effects of changing hardness of a chewing substance on these three variables. Cortically induced rhythmic jaw movements of a crescent-shaped pattern were induced by electrical stimulation of the cerebral cortical masticatory area in the anesthetized rabbit. The axially directed masticatory force was recorded with a small force-displacement transducer mounted on the ground surface of the lower molars. EMGs were recorded from the masseter and digastric muscles simultaneously with jaw movements. Five test strips of polyurethane foam of different hardness were prepared and inserted between the upper molar and the transducer during the movements. The peak, impulse, and buildup speed of the masticatory force increased with strip hardness, whereas duration of the exerted force did not vary with strip hardness. The integrated activity and duration of the masseteric EMG bursts also increased with strip hardness. The integrated EMG activity of the digastric bursts was weakly related to strip hardness, whereas the duration was not. The minimum gape increased with strip hardness, but the maximum gape did not. The horizontal excursion of the jaw did not vary in a hardness-dependent manner, although it was greater in the cycles with strip application than in the cycles without strip application. Deprivation of periodontal sensation by cutting the nerves to the teeth reduced the buildup speed of the force, maximum gape, net gape, and horizontal jaw movements. The denervation also elongated the force duration and that of masseteric EMG bursts. However, the rate of the hardness-dependent changes in the above parameters did not alter after denervation. The latency of the masseteric EMG response to strip application was evaluated before and after denervation. In both conditions, it was > or = 6 ms in approximately 70% of the cycles and <6 ms in the remaining approximately 30%, which cannot be explained by a simple reflex mechanism. On the basis of the analysis of correlation coefficients, the masseteric integrated EMG seemed to be a good indicator of the peak and impulse of the masticatory force both before and after denervation. We conclude that periodontal afferents would be responsible for a quick buildup of masticatory force and that afferents other than those from periodontal tissue would contribute to the hardness-dependent change of masticatory force during cortically induced rhythmic jaw movements.

Animals↗
PubMed1989

[Modulation of the jaw muscle activity during the rhythmical jaw movement by stimulation of the cortical masticatory area and amygdala in the rabbit].

The effect of each stimulus pulse to the digastric and masseter muscles activities was examined during the rhythmic jaw movement evoked by repetitive electrical stimulation of the cortical masticatory area and amygdala in the rabbit. The stimulus pulse evoked facilitation and suppression in the digastric muscle activity, and suppression and slight facilitation in the masseter muscle activity. No obvious difference in the pattern of the modulation was appeared between the stimulation of the anterior and posterior cortical masticatory area in the digastric muscle activity. In masseter muscle, the stimulation of the anterior cortical masticatory area showed remarkable suppression only, whereas the stimulation of the posterior cortical masticatory area evoked both suppression and facilitation. Lager motor units were received conspicuous modulation than smaller motor units in both muscles. The time course of these modulation was resembled with those of the masseteric and digastric reflexes by stimulation of the cortical masticatory area. We concluded that the modulation evoked by repetitive electrical stimulation of the cortical masticatory area might be occurred by stimulation of the same pathway as evoking the modulation of reflexes. The repetitive electrical stimulation of the amygdala induced rhythmical jaw movement. In the digastric and masseter muscles, the stimulus pulse evoked facilitation, whereas no obvious suppression was appeared. Lager motor unit was modulated remarkably than smaller unit.

Amygdala↗
PubMed1996

Hypoglossal premotor neurons in the rostral medullary parvocellular reticular formation participate in cortically-induced rhythmical tongue movements.

Premotor neurons projecting to the hypoglossal (XII) nucleus and participating in cortically-induced rhythmical tongue movements were defined by extracellular recording in the cat. Two thirds (37/57) of antidromically identified XII premotor neurons sampled in the rostral medullary parvocellular reticular formation showed changes in their firing pattern during cortically-induced rhythmical activity of XII motoneurons. Fifteen of the 37 neurons showed a firing in phase with rhythmical activity of either the medial or lateral branch of the XII nerve (phasic-type). The remaining 22 neurons showed an increase in discharge with no apparent correlation with cortically-induced rhythmical activity of the XII nerve (non-phasic-type). Among the phasic- and non-phasic-type neurons, 30 neurons received inputs from the cortical masticatory area, and 14 neurons received further excitatory inputs from the inferior alveolar nerve. By systematic mapping of the stimulation sites effective for antidromic activation, four phasic-type neurons were confirmed to project to either tongue-protruding or -retracting XII motoneuron pools in accordance with their burst firing, suggesting that the phasic-type premotor neurons contribute to excitation of XII motoneurons during cortically-induced rhythmical activity. It is concluded that there are the XII premotor neurons driving cortically-induced rhythmical activity of XII motoneurons in the rostral medullary parvocellular reticular formation.

Animals↗
PubMed2006

Right-left asymmetries in the whisking behavior of rats anticipate head movements.

Rats use rhythmic movements of their vibrissae (whiskers) to tactually explore their environment. This "whisking" behavior has generally been reported to be strictly synchronous and symmetric about the snout, and it is thought to be controlled by a brainstem central pattern generator. Because the vibrissae can move independently of the head, however, maintaining a stable perception of the world would seem to require that rats adjust the bilateral symmetry of whisker movements in response to head movements. The present study used high-speed videography to reveal dramatic bilateral asymmetries and asynchronies in free-air whisking during head rotations. Kinematic analysis suggested that these asymmetric movements did not serve to maintain any fixed temporal relationship between right and left arrays, but rather to redirect the whiskers to a different region of space. More specifically, spatial asymmetry was found to be strongly correlated with rotational head velocity, ensuring a "look-ahead" distance of almost exactly one whisk. In contrast, bilateral asynchrony and velocity asymmetry were only weakly dependent on head velocity. Bilateral phase difference was found to be independent of the whisking frequency, suggesting the presence of two distinct left and right central pattern generators, connected as coupled oscillators. We suggest that the spatial asymmetries are analogous to the saccade that occurs during the initial portion of a combined head-eye gaze shift, and we begin to develop the rat vibrissal system as a new model for studying vestibular and proprioceptive contributions to the acquisition of sensory data.

Animals↗
PubMed1990

The effects of nanoliter ejections of lidocaine into the pontomedullary reticular formation on cortically induced rhythmical jaw movements in the guinea pig.

In the ketamine/urethane anesthetized guinea pig, electromyographic (EMG) responses of the anterior digastric muscle were studied when loci within the lower brainstem were microejected with lidocaine (2%) during rhythmical jaw movements (RJMs) evoked by repetitive electrical stimulation of the masticatory area of the cortex. The area investigated was between the trigeminal motor nucleus (Mot V) and the rostral pole of the inferior olive. Microejections of lidocaine, contralateral to the cortical stimulus site, into the ventral-medial portion of Mot V where digastric motoneurons are known to be located, resulted in reduction or complete abolishment of the digastric EMG activity ipsilateral to the ejection with no effective change in mean cycle duration (CD) or mean percent normalized integrated amplitude of the contralateral digastric EMG. Microejections of lidocaine, contralateral to the cortical stimulus site, into the ponto-medullary reticular formation in areas that included portions of the caudal nucleus pontis caudalis (PnC), nucleus gigantocellularis (GC), medial nucleus parvocellularis (PCRt), and dorsal paragigantocellularis (dPGC), in most cases produced a bilateral reduction in the mean normalized integrated amplitude and a bilateral increase in the mean cycle duration. In these sites, the bilateral increase in mean cycle duration of digastric EMG bursts was also associated with a significant increase of coefficient of variation in CD. In many cases, microejection of lidocaine completely abolished rhythmical digastric activity, bilaterally. HRP injections into Mot V were performed to determine the locations of trigeminal premotoneurons and their relationship to effective lidocaine sites for rhythmical jaw movement suppression. Retrogradely labeled cells were found mainly in the mesencephalic nucleus of V; trigeminal principal and spinal V sensory nuclei, bilaterally; and within the intermediate and lateral regions of reticular formation, bilaterally. No labeling was found in the medial reticular formation, including the nucleus gigantocellularis and dorsal paragigantocellularis.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2001

Rhythmic feet movements while falling asleep.

During the wake-sleep transition and sleep, diverse motor phenomena such as hypnagogic foot tremor may occur in the lower extremities. We investigated the relevance of this phenomenon in 375 consecutive subjects examined polysomnographically in a sleep disorders center. Rhythmic feet movements while falling asleep (RFM) were found in 28 subjects (7.5%). RFM occurred mostly as single, short series with a duration of between 10 and 15 seconds. They had a high night-to-night variability and were detected as rhythmic, oscillating movements of the whole foot or toes. Surface electromyographic (EMG) recordings displayed series of repetitive phasic bursts with a periodicity mostly between 1 and 2 per second. Single EMG burst duration varied between 300 and 700 msec. RFM at highest intensity occurred during presleep wakefulness, and usually persisted in sleep stages 1 and 2. RFM did not have a major sleep-disturbing effect in any of the affected subjects. Due to its high prevalence and the lack of a major sleep-disturbing effect, short series of RFM could be considered a quasiphysiological phenomenon. However, in more severe forms of RFM with evidence of a sleep-disturbing effect, RFM should be considered abnormal.

Adolescent↗
PubMed2002

Neural activities in the substantia nigra modulated by stimulation of the orofacial motor cortex and rhythmical jaw movements in the rat.

Neurons related to jaw movements in the substantia nigra pars reticulata were explored by examining changes in their neural activities in response to electrical stimulation of the orofacial sensorimotor cortex and during rhythmical jaw movements induced by mechanical stimulation applied to the oral cavity in the rat. Out of 80 neurons tested, 59 showed changes in their firing patterns of activities in response to the electrical stimulation of the cortex. The responding neurons were mainly located in the dorsolateral part of the substantia nigra pars reticulata. The substantia nigra pars reticulata neurons showing responses were classified into the following five types according to their response patterns: (1) an inhibition preceded by an early excitation and followed by a late excitation (n = 26), (2) an inhibition preceded by an early excitation but not followed by a late excitation (n = 7), (3) an inhibition not preceded by an early excitation but followed by a late excitation (n = 2), (4) an inhibition without early or late excitations (n = 7) and (5) an excitation without an inhibition (n = 17). Out of 18 neurons responding to the cortical stimulation, 11 (61.1%) increased or decreased their neural activities during rhythmical jaw movements. Some of these neurons had a projection to the lateral part of the superior colliculus (n = 5) and/or to the parvicellular reticular formation (n = 2). These results provide first neurophysiological evidence for neurons in the dorsolateral part of the substantia nigra pars reticulata with inputs from and outputs to the areas related to jaw movements. These neurons may participate in the control of jaw movements in the rat.

Action Potentials↗