Oral Motor Control Research Articles

Translating the Timing of Developmental Benchmarks in Short-Tailed Opossums (Monodelphisdomestica) to Facilitate Comparisons with Commonly Used Rodent Models

Introduction: The gray short-tailed opossum, Monodelhis domestica (M. domestica), is a widely used marsupial model species that presents unique advantages for neurodevelopmental studies. Notably their extremely altricial birth allows manipulation of postnatal pups at timepoints equivalent to embryonic stages of placental mammals. A robust literature exists on the development of short-tailed opossums, but many researchers working in the more conventional model species of mice and rats may find it daunting to identify the appropriate age at which to conduct experiments. Methods: Here, we present detailed staging diagrams taken from photographic observations of 40 individual pups, in 6 litters, over 25 timepoints across postnatal development. We also present a comparative neurodevelopmental timeline of short-tailed opossums (M. domestica), the house mouse (Mus musculus), and the laboratory rat (Rattus norvegicus) during embryonic as well as postnatal development, using timepoints taken from this study and a review of existing literature, and use this dataset to present statistical models comparing the opossum to the rat and mouse. Results: One aim of this research was to aid in testing the generalizability of results found in rodents to other mammalian brains, such as the more distantly related metatherians. However, this broad dataset also allows the identification of potential heterochronies in opossum development compared to rats and mice. In contrast to previous work, we found broad similarity between the pace of opossum neural development with that of rats and mice. We also found that development of some systems was accelerated in the opossum, such as the forelimb motor plant, oral motor control, and some aspects of the olfactory system, while the development of the cortex, some aspects of the retina, and other aspects of the olfactory system are delayed compared to the rat and mouse. Discussion: The pace of opossum development is broadly similar to that of mice and rats, which underscores the usefulness of this species as a compliment to the more commonly used rodents. Many features that differ the most between opossums and rats and mice were either clustered around the day of birth and were features that have functional importance for the pup immediately after or during birth, or were features that have reduced functional importance for the pup until later in postnatal development, given that it is initially attached to the mother.

A scoping review of music-based interventions for swallowing difficulties: implications for treating older adults with presbyphagia.

Presbyphagia refers to age-related changes in the swallowing mechanism (e.g., reduced skeletal muscle strength that decreases bolus control). If left untreated, these changes can lead to dysphagia, which refers to impaired swallowing (e.g., coughing or choking when eating). Given that swallowing difficulties are common among older adults that they make up the fastest growing age group globally, the need for interventions to address presbyphagia is gaining urgency. To begin to address this need, we conducted a scoping review to analyze music therapy research aimed at enhancing swallowing function. The objective was to identify key intervention characteristics and propose clinical implications for treating presbyphagia using music therapy. This review followed the methodological frameworks outlined by Arksey and O'Malley and Levac et al. and used the Preferred Reporting Items for Systematic Reviews and Meta-Analysis for Scoping Reviews for analysis and reporting. Four electronic databases (i.e., ProQuest, PubMed, RISS, Web of Science) were searched for quantitative and qualitative studies in English or Korean that used music-based interventions to address swallowing function in older adults. Content analysis was conducted to identify and compare the main features of music interventions for swallowing difficulties among older adults. Ten articles were identified and analyzed. It was found that three core components-respiration, vocalization, and singing-were employed to enhance swallowing function in populations with neurological impairments, dementia, or head and neck cancer. Notably, actions closely linked to swallowing function, such as laryngeal elevation and oral movements, were utilized therapeutically to speak or sing. Based on these characteristics, clinical implications are proposed to address presbyphagia. Singing entails a systematic and focused incorporation of stepwise activities that can be used to address swallowing disorders. In this context, critical clinical implications that music therapists should consider when treating individuals with presbyphagia include warmup breathing, vocalizing targeting laryngeal control, and singing targeting oral motor control. This review can contribute to the expansion of music therapy with older adults and the advancement of music therapy techniques.

Oromotor skills in autism spectrum disorder: A scoping review.

Oromotor functioning plays a foundational role in spoken communication and feeding, two areas of significant difficulty for many autistic individuals. However, despite years of research and established differences in gross and fine motor skills in this population, there is currently no clear consensus regarding the presence or nature of oral motor control deficits in autistic individuals. In this scoping review, we summarize research published between 1994 and 2022 to answer the following research questions: (1) What methods have been used to investigate oromotor functioning in autistic individuals? (2) Which oromotor behaviors have been investigated in this population? and (3) What conclusions can be drawn regarding oromotor skills in this population? Seven online databases were searched resulting in 107 studies meeting our inclusion criteria. Included studies varied widely in sample characteristics, behaviors analyzed, and research methodology. The large majority (81%) of included studies report a significant oromotor abnormality related to speech production, nonspeech oromotor skills, or feeding within a sample of autistic individuals based on age norms or in comparison to a control group. We examine these findings to identify trends, address methodological aspects hindering cross-study synthesis and generalization, and provide suggestions for future research.

Percepção dos fonoaudiólogos sobre alterações miofuncionais orofaciais em sujeitos com Síndrome Congênita pelo Zika Vírus

ABSTRACT Purpose: to investigate the profile of speech-language-hearing therapists from Northeastern Brazil assisting children presented with congenital Zika syndrome and their perception of these children’s orofacial myofunctional aspects and speech-language-hearing intervention procedures. Methods: a cross-sectional observational study with quantitative/qualitative analysis. The data collection instrument was an online questionnaire with 34 items on the speech-language-hearing therapists’ sociodemographic information and perception of the study topic. The sample comprised 23 speech-language-hearing therapists from the nine Northeastern states. Results: altogether, 96% of the sample were females. Most professionals had more than 3 years of experience with congenital Zika syndrome. Concerning stomatognathic system characterization, the professionals described a greater degree of change in aspects of orofacial muscle posture and mobility. Regarding oral functions, they perceived greater changes in speech and swallowing liquids and solid foods. There was a greater degree of change in masticating solids than in swallowing liquids. Conclusion: most speech-language-hearing therapists in the research had a specialization degree, especially in dysphagia and oral-motor control. Most of them had more than 3 years of experience following up with children with congenital Zika syndrome, which indicates a satisfactory time working with this population to help identify orofacial myofunctional changes in them. The professionals stated that orofacial muscle posture and mobility, speech, and swallowing liquids and solid foods were the most changed aspects.

Voice Onset Time in Healthy Young and Old Adults

Objectives: This study aimed to investigate age related changes in articulatory control by examining whether there were differences between young and elderly adults in their voice onset time (VOT). Methods: 16 adults over the age of 65 and 16 adults aged between 18-39 years old participated in this study. The experimental task consisted of 9 plosives, categorized by place of articulation and phonation type, paired with the vowel /a/ to form 2 syllable VCV non-words. Participants’ voice samples were analyzed using Praat. VOT mean was used to examine group differences in VOT and coefficient of variation (CoV) was used to examine group differences in VOT variability. Results: There were significant differences in VOT mean according to age group, phonation type, and place of articulation. The elderly adults had a longer VOT compared to the young adults with significant differences for place of articulation in velar plosives and significant differences for phonation type in aspirated plosives. There were significant differences in VOT CoV according to age group and phonation type. The elderly adults had higher VOT and CoV compared to the young adults with a significant difference in lenis plosives. Conclusion: The results of this study show that elderly adults have longer VOT durations and irregular articulatory control, reflected by higher VOT variability, compared to younger adults. These results may reflect age related declines in the coordination of the speech mechanism and reduced oral motor control.

Listener Detection of Objectively Validated Acoustic Features of Speech in Huntington’s Disease

Subtle progressive changes in speech motor function and cognition begin prior to diagnosis of Huntington's disease (HD). To determine the nature of listener-rated speech differences in premanifest and early-stage HD (i.e., PreHD and EarlyHD), compared to neurologically healthy controls. We administered a speech battery to 60 adults (16 people with PreHD, 14 with EarlyHD, and 30 neurologically healthy controls), and conducted a cognitive test of processing speed/visual attention, the Symbol Digit Modalities Test (SDMT) on participants with HD. Voice recordings were rated by expert listeners and analyzed for acoustic and perceptual speech features. Listeners perceived subtle differences in the speech of PreHD compared to controls, including abnormal pitch level and speech rate, reduced loudness and loudness inflection, altered voice quality, hypernasality, imprecise articulation, and reduced naturalness of speech. Listeners detected abnormal speech rate in PreHD compared to healthy speakers on a reading task, which correlated with slower speech rate from acoustic analysis and a lower cognitive performance score. In early-stage HD, continuous speech was characterized by longer pauses, a higher proportion of silence, and slower rate. Differences in speech and voice acoustic features are detectable in PreHD by expert listeners and align with some acoustically-derived objective speech measures. Slower speech rate in PreHD suggests altered oral motor control and/or subtle cognitive deficits that begin prior to diagnosis. Speakers with EarlyHD exhibited more silences compared to the PreHD and control groups, raising the likelihood of a link between speech and cognition that is not yet well characterized in HD.

Speech Disorders in Dysgnathic Adult Patients in the Field of Severity of Primary Dysfunction

The normative functioning of the stomatognathic system and masticatory apparatus requires specific coordination between several structures such as teeth with good occlusion, tongue without ankyloglossia or thrusting, and well-balanced facial muscles. This study aimed to evaluate the influence of non-normative primary functions such as breathing, swallowing, biting and chewing on the consonant pronunciation outcome in adults affected with facial skeletal deformities. Moreover, the authors would like to promote a new kind of speech therapy-orthognathic speech therapy. A total of 181 adults affected by skeletal class II and III malocclusion were included, along with the relationship between the malocclusion, speech deficiency (20 phonemes tested) and primary function disorders, in the subjects before and after surgical correction. The impact of surgery on pronunciation and primary function improvement and types of Polish phonemes most often misarticulated by Polish adults were also examined. Patients underwent combined treatment and received a full speech pathology examination. The treatment improved speech (p < 0.05), and primary functions (p < 0.05). Palatal, alveolar (p < 0.05), fricatives (p < 0.05), and labiodental consonant pronunciation (p < 0.05) improved. The surgical correction of malocclusion leads to better oral motor control and articulation of Polish consonants in adults.

Visual feedback of the tongue influences speech adaptation to a physical modification of the oral cavity.

Studies examining sensorimotor adaptation of speech to changing sensory conditions have demonstrated a central role for both auditory and somatosensory feedback in speech motor learning. The potential influence of visual feedback of oral articulators, which is not typically available during speech production but may nonetheless enhance oral motor control, remains poorly understood. The present study explores the influence of ultrasound visual feedback of the tongue on adaptation of speech production (focusing on the sound /s/) to a physical perturbation of the oral articulators (prosthesis altering the shape of the hard palate). Two visual feedback groups were tested that differed in the two-dimensional plane being imaged (coronal or sagittal) during practice producing /s/ words, along with a no-visual-feedback control group. Participants in the coronal condition were found to adapt their speech production across a broader range of acoustic spectral moments and syllable contexts than the no-feedback controls. In contrast, the sagittal group showed reduced adaptation compared to no-feedback controls. The results indicate that real-time visual feedback of the tongue is spontaneously integrated during speech motor adaptation, with effects that can enhance or interfere with oral motor learning depending on compatibility of the visual articulatory information with requirements of the speaking task.

Oral Fine Motor Control of Teeth Treated with Endodontic Microsurgery: A Single-Blinded Case-control Study

IntroductionPeriodontal mechanoreceptors (PMRs) are refined neural receptors present in abundance at the root apex and have a pivotal role in oral fine motor control. This case-control study aimed to evaluate the oral fine motor control of teeth treated with endodontic microsurgery (EMS) in comparison with the control teeth using a standardized behavioral biting task. MethodsFourteen eligible participants performed 5 trials of an oral fine motor control task that involved holding and splitting half of a peanut positioned on a force transducer with their EMS treated tooth and its contralateral control incisor tooth (28 teeth in total). The outcome variables were the mean food holding force, intra- and intertrial variability of the holding force, food splitting force, splitting duration, and the frequency of the stepwise splitting phase. The data were analyzed with parametric and nonparametric tests. ResultsThe results showed no statistically significant differences in the holding force, inter- and intratrial variability of the holding force, splitting force, or splitting duration between the teeth treated with EMS and the control (P > .05). However, there was a significantly higher frequency of stepwise ramp increase during the splitting phase with EMS treated teeth compared with the control (48% and 37%, respectively; P < .05). ConclusionsEMS treated teeth showed similar force regulation and oral fine motor control as the contralateral control. The findings of this study suggest that EMS treatment does not perturb the sensory information of PMRs and maintains the force regulation and oral fine motor control of the teeth.

Comparative study on the effect of oral motor intervention protocols on oral motor skills of preterm infants from tertiary care hospital in metropolitan city: pilot study

Background: Premature infants often have feeding difficulties leading to morbidity or developmental co-morbidities. Premature infant oral motor intervention (PIOMI), has shown the positive effects on feeding progression of the premature infants. PIOMI with the massage technique, may help in improving oral motor activity, weight gain in preterm infants along with better neurobehavioral organization. The study was done to analyse effect of this combined protocol on achieving oral motor control and Neurobehavioral state regulation and evaluate its efficacy against PIOMI.Methods: A total 72 clinically stable infants admitted in premature care unit, fulfilling inclusion criterion were enrolled. They were allocated in control and experimental group. Infants from control group received PIOMI and experimental group received PIOMI with massage therapy (M technique), for 10 minutes each day. Data was collected for oral motor abilities, behavioural assessment, weight and day of achieving full feeds.Results: Gestational age at full feeds was 33.65 weeks and 32.89 weeks in control and experimental groups respectively with ‘p’ value 0.002. The number of days of full feed in experimental group was 3.7 days earlier (p=0.04). Infants from experimental group showed higher oral motor score and more weight gain with significant difference The behavioral regulation in infants of both the groups improved after 8 day.Conclusions: PIOMI with M technique was well tolerated by preterm infants. The modified protocol has resulted in achieving early oral feeds and reducing hospital stay. It has also shown the benefit of behavioural regulation along with better oral motor control.

Developmental and age-related changes in sensorimotor regulation of biting maneuvers in humans

Previous studies indicated distinct differences in biting and chewing behaviors between children and adults. However, these studies used different methodologies and failed to study age-related changes in the fine motor control of biting from childhood to adulthood. Therefore, this study aimed to investigate age-related changes in oral fine motor control in healthy children in comparison to adults. Sixty-five healthy children (3–17 years) were equally divided into five age-groups based on their dental eruption stages. Each participant was asked to hold half a peanut rested on a force transducer between two opposing anterior teeth for 3–4 s before splitting it. The force applied on the transducer was continuously monitored and recorded during food holding and splitting. The data obtained from the children subgroups were compared to an adult group (18–35 years). Results showed that the force regulation during food manipulation was higher and more variable in children with primary to early-permanent dentition stages compared to adults. Additionally, children with primary and early-mixed dentition showed longer food splitting duration than adults and exhibited a predominantly step-wise ramp-increase of force. The results of the present study showed age-related changes in fine motor control of food biting maneuvers. The results of the study also suggested that younger children with primary dentition show signs of immature oral fine motor control. However, with an increase in age and the accompanying structural changes, the oral fine motor control eventually transits to a more matured “adult-like” biting maneuvers.

Tongue function and swallowing in individuals with temporomandibular disorders.

The tongue participates in the oral phase of swallowing by pushing the food bolus toward the oropharynx. This relationship between tongue function and swallowing is little addressed addressed in individuals with temporomandibular dysfunction (TMD).Objective:To analyze the association of functional tongue conditions on swallowing in individuals with TMD.Methodology:After approval by the Institutional Review Board, the study was conducted on 30 individuals of both sexes, aged 18 to 28 years, with TMD, and not treated for the disorder. Tongue function was assessed as to the mobility, pressure, and oral motor control. Swallowing was analyzed by clinical assessment during ingestion of solid (wafer biscuit) and liquid (water). Data regarding mobility and swallowing were collected using the orofacial myofunctional evaluation protocol. Tongue pressure was measured by the Iowa Oral Performance Instrument, during elevation, protrusion, swallowing, and resistance test. The oral motor control was assessed by the oral diadochokinesis (DDK) test by rapid and repeated emissions of syllables “ta” and “ka”. Data were statistically analyzed by the Spearman correlation coefficient, at a significance level of 5%.Results:Relationships were found between tongue function and swallowing for the following aspects: mobility (r=0.741), pressure in protrusion (r=-0.366), swallowing of saliva (r=-0.499), mean DDK rate in emissions “ta” (r=-0.424) and “ka” (r=-0.446), and mean DDK period in emissions “ta” (r=0.424) and “ka” (r=0.446). Thus, the greater the change in tongue mobility, the lower the tongue pressure in protrusion and swallowing of saliva, the lower the emissions per second, the longer the mean time between vocalizations, and the worse the swallowing of individuals with TMD.Conclusion:The functional conditions of the tongue regarding mobility, pressure, and oral DDK were associated with swallowing in individuals with TMD.

Premature infant oral motor intervention (PIOMI) with and without massage therapy on social emotional development in preterm infants

Background: Feeding functions are generally affected in preterm infants. This has long-term impact on emotional development, social learning, and health. Occupational therapists use a variety of interventions such as premature infant oral motor intervention (PIOMI), Infant massage (IM) for improving oral motor control and neuro-behavioral status of preterm infant. PIOMI has positive effects on oral motor functions. IM is recognized as a developmentally supportive intervention aimed at decreasing infant stress and optimizing the infant's sensory experience on long-term development. The current study intends to observe the effect of PIOMI and combined effect of PIOMI with IM on social and emotional development of preterm infants. Objective: The aim was to evaluate the effect of PIOMI and combined effect of PIOMI with IM on social-emotional development of preterm infants. Study Design: Prospective, experimental, design was chosen for this research. Methods: Preterm infants (32–36 weeks) who were hemodynamically stable and satisfying the inclusion criteria were allocated into Group A and Group B randomly divided into 30 subjects in each group. Group A received PIOMI of 10 min session, twice a day. Group B received PIOMI along with IM therapy (IM) of 10 min session twice a day, till they achieved full oral feeds. The infants were evaluated at 2 and 6 months of corrected age on Ages and Stages Questionnaire Social Emotional-2 (ASQ: SE-2) scale to evaluate the long-term effect of intervention on social-emotional development of preterm infants. Results: Thirty infants from Group A enrolled for study, 25 infants followed up at 2 months of corrected age. On social emotional-2 (ASQ: SE-2), they scored mean score of 30.4 ± standard deviation (SD) 7.4, 95% confidence interval CI: (27.66, 33.14), On follow-up at 6 months of corrected age, there was an increase in mean scores to 46.2 ± SD 11.2, 95% CI: (41.7, 50.7). Out of thirty infants, the twenty-eight infants from Group B followed up at 2 months of corrected age. On ASQ: SE-2 they scored as mean 18.4 ± SD 4.5, 95% CI: (16.66, 20.14).This group also showed increase of mean scores at 6 months of corrected age to 28.2 ± SD 8.14, 95% CI: (25.04, 30.36). Infants receiving PIOMI with IM showed better social-emotional development in preterm infants as compared to those received only PIOMI at 2 and 6 months. The marked improvement was seen in components such as social interaction, self-regulation, and communication. Conclusion: Preterm infants from both the groups showed good social emotional development, whereas preterm infants who received PIOMI along with IM therapy showed better self-regulation and interaction due to graded tactile stimulations received during therapy, which also enhanced interaction with caregivers.

Effects of Chronic and Experimental Acute Masseter Pain on Precision Biting Behavior in Humans.

Chronic pain in the orofacial region is common worldwide. Pain seems to affect the jaw motor control. Hence, temporomandibular disorders (TMD) are often accompanied by pain upon chewing, restricted mouth opening and impaired maximal bite forces. However, little is known on the effects of pain, in particular the effects of chronic jaw muscle pain on precision biting. The aim of the study was to investigate the effect of chronic and acute jaw muscle pain on oral motor control during precision biting in humans. Eighteen patients with chronic masseter muscle pain and 18 healthy participants completed the experiment. All participants were examined according to the Diagnostic Criteria for TMD. Experimental acute pain was induced by bilateral, simultaneous sterile hypertonic saline infusions into the healthy masseter muscles. A standardized hold and split biting task was used to assess the precision biting. The data was analyzed with non-parametric statistical tests. The results showed no significant differences in the hold forces, split forces, durations of split or peak split rates within or between the pain and pain-free conditions. The mean split rate increased significantly compared to baseline values both in the chronic patients and the pain-free condition. However, this increase was not evident in the experimental acute pain condition. Further, there were no significant differences in the mean split rates between the conditions. The data suggest that jaw muscle pain does not seem to alter precision biting in humans, however, the possibility that a nociceptive modulation of spindle afferent activity might have occurred but compensated for cannot be ruled out.

Vibratory stimulus to the masseter muscle impairs the oral fine motor control during biting tasks

PurposeTo investigated the effect of vibratory stimulus on masseter muscles during oral fine motor biting tasks. MethodsSixteen healthy individuals (age: 24.5 ± 2.4 years) participated in experiment I during which the participants were asked to “hold and split” half a roasted peanut placed on a force transducer with their front teeth. The participant performed ten series with ten trials of the “hold and split” behavioral task while vibratory stimulus was applied on the masseter muscle every alternate series. Further, fourteen participants participated (age: 25.2 ± 4.8 years) in experiment II during which they performed a series each of the behavioral task at baseline, an adjusted baseline without and with vibration as well as with and without visual feedback. Hold and split forces along with the variability of hold force and duration and force rate during the split were measured. ResultsThe results of the study showed an increase in the magnitude of the hold force (P = 0.002), force rate during the split (P < 0.001) and a significant decrease in the duration of split (P < 0.001) due to the vibratory stimulus. However, there was no significant effect of the vibratory stimulus on the variability of hold forces (P = 0.879) or mean split force (P = 0.683) during the “hold and split” behavioral task. The results of experiment II also showed an increase in hold force due to the vibratory stimulus (P < 0.001). ConclusionsVibratory stimulus to the masseter muscles impairs the oral force control during a standardized biting task and provide further insight into the sensorimotor regulation of the masticatory system.

Can muscle vibration be the future in the treatment of cerebral palsy-related drooling? A feasibility study.

Background: Drooling is an involuntary loss of saliva from the mouth, and it is a common problem for children with cerebral palsy (CP). The treatment may be pharmacological, surgical, or speech-related. Repeated Muscle Vibration (rMV) is a proprioceptive impulse that activates fibers Ia reaching the somatosensory and motor cortex. Aim: The aim of the study is to evaluate the effectiveness of rMV in the treatment of drooling in CP. Design, setting and population: This was a rater blinded prospective feasibility study, performed at the “Gli Angeli di Padre Pio” Foundation, Rehabilitation Centers (Foggia, Italy), involving twenty-two CP patients affected by drooling (aged 5-15, mean 9,28 ± 3,62). Children were evaluated at baseline (T0), 10 days (T1), 1 month (T2) and 3 months (T3) after the treatment. Methods: The degree and impact of drooling was assessed by using the Drooling Impact Scale (DIS), the Drooling Frequency and Severity Scale (DFSS), Visual Analogue Scale (VAS) and Drooling Quotient (DQ). An rMV stimulus under the chin symphysis was applied with a 30 min protocol for 3 consecutive days. Results: The statistical analysis shows that DIS, DFSS, VAS, DQ improved with significant differences in the multiple comparisons between T1 vs T2, T1 vs T3 and T1 vs T4 (p≤0.001). Conclusion This study demonstrates that rMV might be a safe and effective tool in reducing drooling in patients with CP. The vibrations can improve the swallowing mechanisms and favor the acquisition of the maturity of the oral motor control in children with CP.

Outpatient Treatment Based on Self-Management Strategies for Chronic Drooling in Two Children

Drooling is a distressing condition, which is often caused by reduced oral motor control associated with a neurological disorder. It has significant medical, practical and psychosocial impact on children or youth and their families. Therefore, treatment is necessary. Although behavioural therapy for drooling shows promising results, it is generally time- and cost-intensive. For this reason, alternative ways to provide behavioural treatment for chronic drooling need to be explored. In a pair of case studies, the feasibility and potential of an outpatient variant of a behavioural treatment programme for drooling based on self-management strategies was researched with two children with oral motor difficulties. In a three week programme, these children were taught to perform a self-management routine in order to achieve saliva control during regular visits to the child rehabilitation centre. In addition, their parents and teachers were taught to prompt the self-management routine and instructed to provide additional practice at home and at school. In doing so, they were offered support by means of telehealth and personal contact. At the end of the treatment programme, both children showed a significant decrease in drooling severity. Their parents and teachers were satisfied with the treatment effect. Although the present treatment programme showed promising results, further adaptions are necessary to make the treatment programme more widely accessible.

Coupling dynamics in speech gestures: amplitude and rate influences

Speech is a complex oral motor function that involves multiple articulators that need to be coordinated in space and time at relatively high movement speeds. How this is accomplished remains an important and largely unresolved empirical question. From a coordination dynamics perspective, coordination involves the assembly of coordinative units that are characterized by inherently stable coupling patterns that act as attractor states for task-specific actions. In the motor control literature, one particular model formulated by Haken et al. (Biol Cybern 51(5):347-356, 1985) or HKB has received considerable attention in the way it can account for changes in the nature and stability of specific coordination patterns between limbs or between limbs and external stimuli. In this model (and related versions), movement amplitude is considered a critical factor in the formation of these patterns. Several studies have demonstrated its role for bimanual coordination and similar types of tasks, but for speech motor control such studies are lacking. The current study describes a systematic approach to evaluate the impact of movement amplitude and movement duration on coordination stability in the production of bilabial and tongue body gestures for specific vowel-consonant-vowel strings. The vowel combinations that were used induced a natural contrast in movement amplitude at three speaking rate conditions (slow, habitual, fast). Data were collected on ten young adults using electromagnetic articulography, recording movement data from lips and tongue with high temporal and spatial precision. The results showed that with small movement amplitudes there is a decrease in coordination stability, independent from movement duration. These findings were found to be robust across all individuals and are interpreted as further evidence that principles of coupling dynamics operate in the oral motor control system similar to other motor systems and can be explained in terms of coupling mechanisms between neural oscillators (organized in networks) and effector systems. The relevance of these findings for understanding motor control issues in people with speech disorders is discussed as well.

Perturbed oral motor control due to anesthesia during intraoral manipulation of food

Sensory information from periodontal mechanoreceptors (PMRs) surrounding the roots of natural teeth is important for optimizing the positioning of food and adjustment of force vectors during precision biting. The present experiment was designed to test the hypothesis; that reduction of afferent inputs from the PMRs, by anesthesia, perturbs the oral fine motor control and related jaw movements during intraoral manipulation of morsels of food. Thirty healthy volunteers with a natural dentition were equally divided into experimental and control groups. The participants in both groups were asked to manipulate and split a spherical candy into two equal halves with the front teeth. An intervention was made by anesthetizing the upper and lower incisors of the experimental group while the control group performed the task without intervention. Performance of the split was evaluated and the jaw movement recorded. The experimental group demonstrated a significant decrease in measures of performance following local anesthesia. However, there was no significant changes in the duration or position of the jaw during movements in the experimental and control group. In conclusion, transient deprivation of sensory information from PMRs perturbs oral fine motor control during intraoral manipulation of food, however, no significant alterations in duration or positions of the jaw during movements can be observed.

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.