Oral Motor Behavior Research Articles

Assessing the knowledge of dental practitioners on development of occlusion and eruption patterns

Background: An ideal occlusion is the perfect interdigitation of the upper and lower teeth. The emergence of the primary dentition is a valuable time for the development of oral motor behavior and the acquisition of masticator skills. The clinician needs to be able to predict the influence that different treatment options will have on the occlusion and dentition when the child’s development is complete. Aim: The aim of this study is to assess the knowledge among dentists treating patients about the development of occlusion and eruption patterns in children, which is helpful in orthodontic referrals. Materials and Methods: A closed-ended questionnaire comprising 15 questions based on eruption sequence, pattern, and occlusion was given to 500 dental practitioners. Data were analyzed by computing the percentage response for each question. Results: The results show that 96% were aware of the Broadbent phenomenon/ugly duckling stage. About 72% knew about the sequence of eruption of primary teeth. Conclusion: This study concludes that most of the dental practitioners treating patients are aware of the development of occlusion and eruption patterns.

Turkish Version of the Mastication Observation and Evaluation (MOE) Instrument: A Reliability and Validity Study in Children.

The Mastication Observation and Evaluation (MOE) instrument is an objective assessment of the chewing process in children. This study aimed to translate the MOE into Turkish and to test its reliability and validity in children with cerebral palsy (CP). A total of 53 children with CP and 27 typical children were included in the study. The MOE was translated from Dutch into Turkish by using the forward, backward, forward translation method. The internal consistency, intra- and inter-observer reliability, criterion, and discriminant validity of the Turkish version of the MOE (T-MOE) were investigated. Internal consistency was excellent with a Cronbach's alpha value of 0.98. The Intraclass correlation coefficient ranged from 0.89 to 0.97 for intra-rater reliability and from 0.86 to 0.94 for inter-rater reliability. The median score from Karaduman Chewing Performance Scale (KCPS) was 7 (min = 1, max = 8). All of the items in the T-MOE and the total T-MOE score had a negative and strong correlation with the KCPS score. Typical children without chewing disorders had greater T-MOE scores than the children with CP suffering from chewing disorders (p < 0.01). The T-MOE is a reliable and valid instrument for evaluating the observed oral motor behaviors of chewing function in children. It can be used in clinical practice and research.Clinical trial number: NCT03811353.

Oral Motor Abilities Are Task Dependent: A Factor Analytic Approach to Performance Rate

ABSTRACTMeasures of performance rates in speech-like or volitional nonspeech oral motor tasks are frequently used to draw inferences about articulation rate abnormalities in patients with neurologic movement disorders. The study objective was to investigate the structural relationship between rate measures of speech and of oral motor behaviors different from speech. A total of 130 patients with neurologic movement disorders and 130 healthy subjects participated in the study. Rate data was collected for oral reading (speech), rapid syllable repetition (speech-like), and rapid single articulator movements (nonspeech). The authors used factor analysis to determine whether the different rate variables reflect the same or distinct constructs. The behavioral data were most appropriately captured by a measurement model in which the different task types loaded onto separate latent variables. The data on oral motor performance rates show that speech tasks and oral motor tasks such as rapid syllable repetition or repetitive single articulator movements measure separate traits.

Dissociating oral motor capabilities: Evidence from patients with movement disorders

Abnormal articulation rate is a frequent symptom in neurogenic speech disorders. Performance rates in speech-like or nonspeech tasks involving the vocal motor apparatus are commonly accepted predictors of speech motor function in general and of articulation rate in particular. However, theoretical arguments and behavioral observations in populations with disordered speech indicate that different oral motor behaviors may be governed by distinct mechanisms. The objective of the present study was to expand our knowledge of the relationship between speech movements, on the one hand, and speech-like and nonspeech oral motor behaviors, on the other, by using a rate paradigm. 130 patients with neurological movement disorders of different origins and 130 neurologically healthy subjects participated in the study. Rate data was collected in a speech task (oral reading/repetition), in speech-like tasks (rapid syllable repetitions), and in nonspeech tasks (rapid single articulator movements of the tongue/lips). The main analyses involved a multiple single-case method, by which we tested for differences among each patient's performance rates on the three task types. The results disclosed statistically significant (classical and strong) dissociations between movement rates obtained from the speech task and those obtained from speech-like and nonspeech oral motor tasks in a number of patients. The findings can be interpreted as reflecting major differences in task demands and underlying control mechanisms. The validity of diagnostic indices for speech obtained from speech-like or nonspeech tasks must thus be called into question.

Fine motor control of the jaw following alteration of orofacial afferent inputs

ObjectiveThe study was designed to investigate if alteration of different orofacial afferent inputs would have different effects on oral fine motor control and to test the hypothesis that reduced afferent inputs will increase the variability of bite force values and jaw muscle activity, and repeated training with splitting of food morsel in conditions with reduced afferent inputs would decrease the variability and lead to optimization of bite force values and jaw muscle activity.Material methodsForty-five healthy volunteers participated in a single experimental session and were equally divided into incisal, mucosal, and block anesthesia groups. The participants performed six series (with ten trials) of a standardized hold and split task after the intervention with local anesthesia was made in the respective groups. The hold and split forces along with the corresponding jaw muscle activity were recorded and compared to a reference group.ResultsThe hold force and the electromyographic (EMG) activity of the masseter muscles during the hold phase were significantly higher in the incisal and block anesthesia group, as compared to the reference group (P < 0.001). However, there was no significant effect of groups on the split force (P = 0.975) but a significant decrease in the EMG activity of right masseter in mucosal anesthesia group as compared to the reference group (P = 0.006). The results also revealed that there was no significant effect of local anesthesia on the variability of the hold and split force (P < 0.677). However, there was a significant decrease in the variability of EMG activity of the jaw closing muscles in the block anesthesia group as compared to the reference group (P < 0.041), during the hold phase and a significant increase in the variability of EMG activity of right masseter in the mucosal anesthesia group (P = 0.021) along with a significant increase in the EMG activity of anterior temporalis muscle in the incisal anesthesia group, compared to the reference group (P = 0.018), during the split phase.ConclusionsThe results of the present study indicated that altering different orofacial afferent inputs may have different effects on some aspects of oral fine motor control. Further, inhibition of afferent inputs from the orofacial or periodontal mechanoreceptors did not increase the variability of bite force values and jaw muscle activity; indicating that the relative precision of the oral fine motor task was not compromised inspite of the anesthesia. The results also suggest the propensity of optimization of bite force values and jaw muscle activity due to repeated splitting of the food morsels, inspite of alteration of sensory inputs.Clinical relevanceSkill acquisition following a change in oral sensory environment is crucial for understanding how humans learn and re-learn oral motor behaviors and the kind of adaptation that takes place after successful oral rehabilitation procedures.

An automated system for quantitative analysis of newborns' oral-motor behavior and coordination during bottle feeding.

In this work a novel unobtrusive technology-aided system is presented and tested for the assessment of newborns' oral-motor behavior and coordination during bottle feeding. A low-cost monitoring device was designed and developed in order to record Suction (S) and Expression (E) pressures from a typical feeding bottle. A software system was developed to automatically treat the data and analyze them. A set of measures of motor control and coordination has been implemented for the specific application to the analysis of sucking behavior. Experimental data were collected with the developed system on two groups of newborns (Healthy vs. Low Birth Weight) in a clinical setting. We identified the most sensitive S features to group differences, and analyzed their correlation with S/E coordination measures. Then, Principal Component Analysis (PCA) was used to explore the system suitability to automatically identify peculiar oral behaviors. Results suggest the suitability of the proposed system to perform an objective technology-aided assessment of the newborn's oral-motor behavior and coordination during the first days of life.

Effects of short-term training on behavioral learning and skill acquisition during intraoral fine motor task

Sensory information from the orofacial mechanoreceptors are used by the nervous system to optimize the positioning of food, determine the force levels, and force vectors involved in biting of food morsels. Moreover, practice resulting from repetition could be a key to learning and acquiring a motor skill. Hence, the aim of the experiment was to test the hypothesis that repeated splitting of a food morsel during a short-term training with an oral fine motor task would result in increased performance and optimization of jaw movements, in terms of reduction in duration of various phases of the jaw movements. Thirty healthy volunteers were asked to intraorally manipulate and split a chocolate candy, into two equal halves. The participants performed three series (with 10 trials) of the task before and after a short-term (approximately 30min) training. The accuracy of the split and vertical jaw movement during the task were recorded. The precision of task performance improved significantly after training (22% mean deviation from ideal split after vs. 31% before; P<0.001). There was a significant decrease in the total duration of jaw movements during the task after the training (1.21 s total duration after vs. 1.56 s before; P<0.001). Further, when the jaw movements were divided into different phases, the jaw opening phase and contact phase were significantly shorter after training than before training (P=0.001, P=0.002). The results indicate that short-term training of an oral fine motor task induces behavior learning, skill acquisition and optimization of jaw movements in terms of better performance and reduction in the duration of jaw movements, during the task. The finding of the present study provides insights into how humans learn oral motor behaviors or the kind of adaptation that takes place after a successful prosthetic rehabilitation.

Assessment of incising ethology in the absence and presence of jaw muscle hyperalgesia in a mouse home cage environment

IntroductionAssessment of oral motor behavior in a mouse is challenging due to the lack of currently available techniques that are non-invasive and allow long-term assessment in a home cage environment. The purpose of this study was to evaluate incising behavior using mouse chow attached to a three-dimensional force transducer that was mounted on the existing home cage. In addition, a persistent hyperalgesia condition was introduced to evaluate the sensitivity of the technique to identify incising behavioral changes. MethodsIncising activity of CD-1 male and female mice (n=48) was evaluated over a 24hour recording session during four baseline and six longitudinal hyperalgesia assessment sessions using custom written software. A pre-clinical persistent pain model was used to induce hyperalgesia in the masseter muscle by repetitive acidic saline injections. Sex and age differences were evaluated for multiple incising variables during both light and dark cycles during baseline and hyperalgesia conditions. ResultsSignificant sex differences were found for multiple incising variables but not for age. Discrete incising frequencies were identified in the range of 4.6–10.4Hz and were reproducibly found in both female and male mice. A significant shift to lower incising frequencies was observed after repetitive acidic saline injections compared to neutral saline injections. This shift to lower frequencies of incising returned to baseline levels after approximately four weeks but was statistically longer in female compared to male mice. Significant differences were also found for chow intake (reduced) and weight change during the hyperalgesia condition. No significant differences were found for total number of incisions or number of incising episodes per day or incising force. ConclusionsThe findings from this study support the use of recording three dimensional incising forces as a sensitive measure of incising behavior. This novel technique allowed the identification of specific incising variables that were differentially affected in female and male mice during a persistent hyperalgesia. The data were collected in the home cage environment with minimal bias such as experimenter interaction. Similar to other dental pain studies, mice were able to maintain normal incising activity levels per day (total incisions, total number of incising episodes) even in the presence of hyperalgesia.

Development of oral motor behavior related to the skill assisted spoon feeding

Milestones in the typical development of eating skills are considered to be nippling (breast or bottle), eating from a spoon, drinking from a cup, biting and chewing.The purpose of this research was to study the development and consolidation of oral motor behavior related to the skill assisted spoon feeding in young infants. The present study longitudinally investigated the development of this skill in 39 healthy children from the start of spoon feeding until the skill was acquired. The Observation List Spoon Feeding with 7 observation items for oral motor behavior and 6 items for abnormal behavior was used. Results showed that infants between 4 and 8 months of age needed 5.7 weeks (SD 2.1), with a range of 8 weeks (from 2 to 10 weeks) to acquire this skill. No significant correlation (p=.109) between age at start spoon feeding and weeks needed to develop the skill was found. During this period oral motor behavior consolidated and abnormal behavior diminished.With this study it is shown that the period in weeks needed to acquire the oral motor behavior for the skill assisted spoon feeding is important in case of feeding problems.

Electrophysiological and morphological properties of rat supratrigeminal premotor neurons targeting the trigeminal motor nucleus

The electrophysiological and morphological characteristics of premotor neurons in the supratrigeminal region (SupV) targeting the trigeminal motor nucleus (MoV) were examined in neonatal rat brain stem slice preparations with Ca(2+) imaging, whole cell recordings, and intracellular biocytin labeling. First, we screened SupV neurons that showed a rapid rise in intracellular free Ca(2+) concentration ([Ca(2+)]i) after single-pulse electrical stimulation of the ipsilateral MoV. Subsequent whole cell recordings were generated from the screened SupV neurons, and their antidromic responses to MoV stimulation were confirmed. We divided the antidromically activated premotor neurons into two groups according to their discharge patterns during the steady state in response to 1-s depolarizing current pulses: those firing at a frequency higher (HF neurons, n = 19) or lower (LF neurons, n = 17) than 33 Hz. In addition, HF neurons had a narrower action potential and a larger afterhyperpolarization than LF neurons. Intracellular labeling revealed that the axons of all HF neurons (6/6) and half of the LF neurons (4/9) entered the MoV from its dorsomedial aspect, whereas the axons of the remaining LF neurons (5/9) entered the MoV from its dorsolateral aspect. Furthermore, the dendrites of three HF neurons penetrated into the principal sensory trigeminal nucleus (Vp), whereas the dendrites of all LF neurons were confined within the SupV. These results suggest that the types of SupV premotor neurons targeting the MoV with different firing properties have different dendritic and axonal morphologies, and these SupV neuron classes may play unique roles in diverse oral motor behaviors, such as suckling and mastication.

Demanda para intervenção fonoaudiológica em uma unidade neonatal de um hospital-escola

OBJETIVO: caracterizar a demanda e intervenção fonoaudiológicas realizadas em recém-nascidos e lactentes que apresentaram alterações no processo de alimentação por via oral, na Unidade Neonatal de um hospital-escola de caráter público. MÉTODOS: trata-se de um estudo retrospectivo, descritivo e de corte transversal. Foi realizada a coleta de dados por meio de consulta a todos os prontuários fonoaudiológicos de recém-nascidos e lactentes internados no período entre março de 2008 e fevereiro de 2010, que receberam ao menos uma avaliação/intervenção fonoaudiológica. RESULTADOS: foram atendidos nesse período 205 recém-nascidos e lactentes internados. Destes sujeitos, 104 atenderam aos critérios de inclusão na pesquisa. A população predominante foi do sexo masculino, composta de recém-nascidos pré-termo, adequados para idade gestacional, baixo peso ao nascimento, em média com 36 semanas de idade gestacional, com diagnósticos mais frequentes de distúrbio respiratório, síndrome ictérica e/ou distúrbio cardiovascular. Dentre os motivos de encaminhamento para avaliação fonoaudiológica predominaram: alteração no comportamento motor oral, avaliação da prontidão para alimentação por via oral e dificuldades no uso do copo. As avaliações foram solicitadas, em sua maioria, por médicos residentes quando os recém-nascidos estavam, em média, com 28 dias de vida. Verificou-se ampliação dos critérios de encaminhamento da equipe para avaliação fonoaudiológica, quando comparados aos critérios descritos na literatura. CONCLUSÕES: esse trabalho permitiu caracterizar a população, a demanda e a intervenção fonoaudiológicas em uma unidade neonatal. Verificou-se que a maioria dos recém-nascidos e lactentes ainda recebe alimentação por via oral sem avaliação fonoaudiológica prévia, o que pode gerar situações de risco para uma alimentação segura e eficiente.

Comportamento motor oral e global de recém-nascidos de mães usuárias de crack e/ou cocaína

OBJETIVO: Analisar o comportamento motor oral e global de recém-nascidos de mães que fizeram uso de crack e/ou cocaína durante a gestação e verificar se há relação entre o desenvolvimento dos sistemas sensório motor oral (SSMO) e motor global. MÉTODOS: Estudo transversal, em que foram avaliados 25 recém-nascidos prematuros e a termo de mães usuárias de crack e/ou cocaína, pareados com outro grupo de 25 recém-nascidos sem o fator em estudo. As avaliações do SSMO e motor global foram realizadas por meio do Instrumento de Avaliação da Prontidão do Prematuro para Início da Alimentação Oral e do Test of Infant Motor Performance (TIMP), respectivamente. Os resultados compararam os escores encontrados nas duas escalas e a relação destes com o uso materno do crack e/ou cocaína durante a gestação. RESULTADOS: No TIMP não foi constatada diferença na comparação entre os escores de recém-nascidos de mães usuárias de crack e/ou cocaína e os de mães não usuárias. No Instrumento de Avaliação da Prontidão do Prematuro para Início da Alimentação Oral, os resultados apresentaram diferença. Foi observada associação entre os resultados de bebês que apresentaram atraso no TIMP com menor escore no Instrumento de Avaliação da Prontidão do Prematuro para Início da Alimentação Oral. CONCLUSÃO: O baixo desempenho observado no Instrumento de Avaliação da Prontidão do Prematuro para Início da Alimentação Oral sugere que as respostas motoras orais estão alteradas pelo uso materno das drogas. A correlação entre os dois instrumentos mostra que o desenvolvimento do SSMO pode estar relacionado ao desenvolvimento motor global.

Somatotopic organization of motor areas in Macaca assamensis

The range and complexity of orofacial movements require sophisticated neural circuitries that provide for the coordination and control of these movements and their integration with other motor patterns such as those associated with breathing and walking. This chapter is dedicated to Jim Lund whose many research studies have made major contributions to our knowledge of the role of brainstem and cerebral cortex in orofacial motor control. Our own investigations using intracortical microstimulation (ICMS), cortical cold block, and single neuron recordings have documented that the face primary motor area (MI) and primary somatosensory area (SI) are involved in the control not only of elemental and learned orofacial movements but also of the so-called semiautomatic movements such as mastication and swallowing, the control of which have been largely attributed in the past to brainstem mechanisms. Recent studies have also documented that neuroplasticity of the face sensorimotor cortex is a feature of humans and animals trained in a novel oral motor behavior, and that it reflects dynamic and adaptive events that can be modeled by behaviorally significant experiences, including pain and other alterations to the oral environment. Furthermore, our findings of the disruptive effects of the face sensorimotor cortex cold block indicate that the face MI and SI are also critical in the successful performance of an orofacial motor skill once it is learned. Future studies aimed at the further demonstration of such changes and at their underlying mechanisms and their sequence of appearance in the face sensorimotor cortex and associated cortical areas represent crucial steps for understanding the intracortical processes underlying neuroplasticity related to oral motor learning and adaptation. In view of the role that cortical neuronal ensembles play in motor execution, learning, and adaptation (Nicolelis and Lebedev, 2009), these studies should include the properties and plasticity of neuronal ensembles in several related cortical areas in addition to a specific focus on single neurones or efferent microzones within the face MI or SI. As recently noted (Martin, 2009; Sessle et al., 2007, 2009), such research approaches are also important for developing improved rehabilitative strategies to exploit these mechanisms in humans suffering from chronic orofacial pain or sensorimotor disorders.

Diurnal and nocturnal drooling in Parkinson’s disease

Drooling as symptom of Parkinson’s disease (PD) has thus far been poorly defined. This uncertainty is reflected by high variations in published prevalence rates. The aim of this study was to investigate the prevalence of saliva loss versus accumulation of saliva as a possible preliminary stage, and diurnal drooling versus nocturnal drooling. In addition, we evaluated the association between drooling severity and the severity of facial and oral motor disorders. We collected age, disease duration, UPDRS III and Hoehn & Yahr stage from 104 consecutive outpatients with PD. Diurnal and nocturnal drooling was evaluated with a validated questionnaire (ROMP-saliva). A speech pathologist, blinded for drooling severity, rated facial expression, involuntary mouth opening and difficulty with nose breathing and also interviewed patients about sleeping position and nose-breathing during the night. Thirty patients (29%) had no complaints with saliva control (‘non-droolers’), 45 patients (43%) experienced accumulation of saliva or only nocturnal drooling (‘pre-droolers’), and 29 (28%) had diurnal drooling (24 of which also drooled during the night; ‘droolers’). The droolers had longer disease duration (10 vs. 7 years, p = 0.01) and drooling was independently associated with involuntary mouth opening (OR = 2.0; 95% CI 1.02–3.99) and swallowing complaints (OR = 1.2; 95% CI 1.03–1.31). Diurnal drooling—defined as dribbling of saliva while awake—is present in about 28% of PD patients. This is less than usually reported. Diurnal drooling typically appeared later in the disease course. The association with oral motor behavior should encourage the development of behavioral treatment approaches.

Después de cien años de uso: ¿las férulas oclusales tienen algún efecto terapéutico?

Occlusal appliances or splints have been used for over a century, generating controversy about their real therapeutic value. This led to an updated review to assess their effects according to scientific evidence. The concept of centric relation and its determination as a starting point of treatment; the use of splints to deprogram; their effect on the oral motor behaviour known as bruxism are discussed. Their effect on EMG activity during resting, swallowing and maximal clenching in the masticatory and neck muscles; their effect on muscular efficiency; their effect decreasing the joint overload; and experimental evidence of the use of several appliances on specific symptoms such as pain and joint noise, are also treated. The true challenge is to generate new knowledge about joint degenerative changes, the craniocervical relationships, tilt and curvature of the cervical spine.

Supranuclear Control of Swallowing

Swallowing is an act requiring complex sensorimotor integration. Using a variety of methods first used to study limb physiology, initial efforts to study swallowing have yielded information that multiple cortical and subcortical regions are active participants. Not surprisingly, the regions activated appear to overlap those involved in both oral and nonoral motor behaviors. This review offers a perspective that considers the supranuclear control of swallowing in light of these physiological similarities.

Pain Coping Strategies for Tension-Type Headache: Possible Implications for Insomnia?

Insomnia has been identified as a risk factor for tension-type headache, although the pathogenesis of sleep disturbance in this population is unclear. The present study examined pain-related self-management strategies in a nonclinical, young-adult sample for preliminary evidence to support a novel hypothesis for the development of insomnia in this population. Self-report data on triggers of headache, pain interference with sleep, and pain-related self-management strategies were analyzed for 32 women with tension-type headache and 33 women with minimal pain who served as controls. The results revealed that a significantly greater proportion of the headache group relative to the control group reported sleep problems as a trigger of headaches, stress as a trigger of headache, and going to sleep as a coping strategy for pain. The headache group also reported significantly higher ratings of pain interference with sleep. Going to sleep was the most commonly used self-management strategy (81%) by headache sufferers and also rated as the most effective strategy (5.5 out of 7.0). These findings suggest that a bidirectional relationship between sleep disturbance and headache is present in this young-adult sample. Furthermore, the frequent use of sleep as a self-management strategy for pain is consistent with the hypothesis that sleep-seeking behavior might be a mediating factor in the development of insomnia among people with tension-type headache. This hypothesis fits within the most widely accepted conceptual model of chronic insomnia and should be further investigated in individuals with both tension-type headache and insomnia.

Speech versus nonspeech: different tasks, different neural organization.

This article reviews the extant studies of the relation of oromotor nonspeech activities to speech production. The relevancy of nonspeech oral motor behaviors to speech motor performance in assessment and treatment is challenged on several grounds. First, contemporary motor theory suggests that movement control is task specific. In other words, it is tied to the unique goals, sources of information, and characteristics of varying motor acts. Documented differences in movement characteristics for speech production versus nonspeech oral motor tasks support this claim. Second, advantages of training nonspeech oral motor tasks versus training speech production are not supported by current principles of motor learning and neural plasticity. Empirical data supports experience-specific training. Finally, functional imaging studies document differences in activation patterns for speech compared with nonspeech oral motor tasks in neurologically healthy individuals.

Early attainment of breastfeeding competence in very preterm infants

To explore the development of breastfeeding capacity in very preterm infants, as an immature sucking behaviour is often mentioned as a barrier in the establishment of breastfeeding in these infants. A prospective descriptive design study in which mothers of 15 infants, born at gestational ages between 26 and 31 weeks, used the Preterm Infant Breastfeeding Behaviour Scale for daily assessments of their infants' oral motor behaviour in hospital. Semi-demand feeding with prescription of a total daily volume of milk was practiced during the transition from scheduled to demand feeding. Breastfeeding was initiated from a postmenstrual age (PMA) of 29 weeks. Obvious rooting, efficient areolar grasp, and repeated short sucking bursts were noted from 29 weeks, and occasional long sucking bursts and repeated swallowing from 31 weeks. The maximum number of consecutive sucks was limited to between 5 and 24 sucks, with a median of 17. Full breastfeeding was attained at a median of 35 weeks, between 32 and 38 weeks. The infants' weight gain when fully breastfed was adequate. Very preterm infants have the capacity for early development of oral motor competence that it sufficient for establishment of full breastfeeding at a low postmenstrual age.

Inhibition of Trigeminal Respiratory Activity by Suckling

The trigeminal motor system is involved in many rhythmic oral-motor behaviors, such as suckling, mastication, swallowing, and breathing. Despite the obvious importance of functional coordination among these rhythmic activities, the system is not well-understood. In the present study, we examined the hypothesis that an interaction between suckling and breathing exists in the brainstem, by studying the respiratory activity in trigeminal motoneurons (TMNs) during fictive suckling using a neonatal rat in vitro brainstem preparation. The results showed that fictive suckling, which was neurochemically induced by bath application of N-methyl-D,L-aspartate and bicuculline-methiodide, or by local micro-injection of the same drugs to the trigeminal motor nucleus, inhibited the inspiratory activities in both respiration TMNs and respiratory rhythm-generating neurons. Under patch-clamp recording, fictive suckling caused membrane potential hyperpolarization of respiration TMNs. We conclude that the brainstem preparation contains an inhibitory circuit for respiratory activity in the trigeminal motor system via the rhythm-generating network for suckling. BIC, bicuculline methiodide; GABA, gamma aminobutyric acid; NMA, N-methyl-D,L-aspartate; NMDA, N-methyl-D-aspartate; and TMN, trigeminal motoneuron.