Jaw Cycle Research Articles

Segmental and Syllabic Articulations: A Descriptive Approach.

This article reports on jaw articulation, in connection with the segmental articulations of tongue tip and lips. The jaw is considered a syllable articulator as it opens and closes for each syllable, and the amount of jaw opening is related to syllable strength, given the same phonemic vowel. Here, we investigate the syllabic and the segmental articulations relationships to the acoustic segments. We analyze electromagnetic articulography data of 18 Southern Swedish speakers by testing hypotheses based on the Descriptive Approach to Segmental Articulations. In this approach, articulatory movements are divided into fast intervals and steady states, and the crucial ("primary") articulators' deceleration and acceleration peaks align with the acoustic segment boundaries. Previous findings on the lips and the tongue tip are confirmed. New results are the jaw as noncrucial ("nonprimary") does not align with the acoustic segment boundaries: Its steady states are shorter than consonant and vowel segments. Moreover, place of articulation of the coda affects the jaw cycle, while syllable type only affects jaw closing. No such effects are found on the edges of the jaw cycle, instead only gender affects jaw deceleration at syllable onset. The jaw is not crucial for the timing of the acoustic segment boundaries; also, syllable borders seem to not be affected by place of segmental articulation. The results strengthen the view of the jaw as syllable articulator providing a frame and the other articulators (e.g., lips and tongue tip) as the segmental articulators providing the content.

3D hyoid and tongue kinematics reveal mechanism of tongue base retraction during swallowing in Didelphis virginiana

In anthropoid primates, tongue base retraction (TBR) is a key event for airway protection and bolus propulsion during swallowing. In macaques, hyoid protraction and elevation during swallowing reduce the oral volume and squeeze the tongue base to retract. This novel hyoid-powered hydraulic TBR mechanism implies that the morphology and position of the hyoid are functionally relevant for TBR performance. However, macaque’s highly derived craniofacial and hyoid morphology precludes inference on the evolutionary history and driving mechanism of TBR across mammal phylogeny at large. Here we use biplanar videoradiography and the XROMM workflow to infer TBR mechanism in Didelphis virginiana through high-resolution 3D hyolingual kinematics. Similar to macaques, Didelphis has an incomplete hyoid cornu, which would enable a large hyoid range of motion that facilitates oral volume reduction. Unlike macaques, Didelphis hyoid has a more posteriorly resting hyoid position. We predict that TBR will occur in Didelphis through a similar hyoid-powered hydraulic mechanism. We find Didelphis deploys TBR during the first opening (O1) phase (liquid) or slow-open phase (solid) of jaw cycle with retraction and elevation of midline posterior tongue markers. Minimal retraction occurs in lateral tongue markers where extrinsic lingual muscles insert. The tongue base and posterior tongue are lengthening, narrowing and increasing in height during TBR, consistent with predictions based on muscular hydrostat model. The tongue base was not isovolumetric during TBR, but the volume change was orders of magnitude smaller than that observed in macaques. Hyoid protraction and elevation occur before and continue throughout TBR, which strongly suggest concurrent reduction of oral volume as well. Our preliminary data suggest the TBR mechanism in opossums may differ in important ways from that utilized by macaques, where opossums could employ a combination of hydrostatic deformation and hydraulic mechanism to drive retraction of tongue base. We provide novel insights into the conservation of TBR across therian mammals and extend our understanding on the form-function relationships between the hyolingual apparatus and swallowing biomechanics. Hinds Fund, University of Chicago This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

An ultrasound study of contextual and syllabic effects in consonant sequences produced under heavy articulatory constraint conditions

The present ultrasound study investigates lingual coarticulatory resistance and differences in tongue configuration and contextual variability for consonants in syllable onset vs coda position in Catalan /iC#Ci/ sequences. In agreement with comparable ultrasound data for /aC#Ca/ sequences reported in an earlier study, coarticulatory resistance turned out to be less for /r/ (which is realized as a trill in onset position and exhibits a more tap-like realization in coda position), /l/ (which is not strongly dark), /s/ and the alveolopalatal /ɲ/ than for /p, t, n, k/. As expected, contextual variability was less for /iC#Ci/ than for /aC#Ca/ sequences due to the highly demanding requirements put on the tongue body by the high front vowel. Regarding the syllable-position-dependent differences, consonants were often longer but not less variable articulatorily in syllable initial than syllable final position. Syllable-position differences in lingual configuration could be ascribed to either a trend for consonants to be more prominent in onset vs coda position or to prominent coarticulatory effects from flanking /i/ rather than from the contextual consonant in the cluster. The conclusion is drawn that the reason why consonants may sound more reduced in coda vs onset position in heterosyllabic clusters is due less to their actual lingual configuration than to their being manifestly shorter and to specific production characteristics which depend not only on the upper articulators but on the jaw cycle as well.

Videofluoroscopic Validation of a Translational Murine Model of Presbyphagia.

Presbyphagia affects approximately 40% of otherwise healthy people over 60 years of age. Hence, it is a condition of primary aging rather than a consequence of primary disease. This distinction warrants systematic investigations to understand the causal mechanisms of aging versus disease specifically on the structure and function of the swallowing mechanism. Toward this goal, we have been studying healthy aging C57BL/6 mice (also called B6), the most popular laboratory rodent for biomedical research. The goal of this study was to validate this strain as a model of presbyphagia for translational research purposes. We tested two age groups of B6 mice: young (4-7 months; n = 16) and old (18-21 months; n = 11). Mice underwent a freely behaving videofluoroscopic swallow study (VFSS) protocol developed in our lab. VFSS videos (recorded at 30 frames per second) were analyzed frame-by-frame to quantify 15 swallow metrics. Six of the 15 swallow metrics were significantly different between young and old mice. Compared to young mice, old mice had significantly longer pharyngeal and esophageal transit times (p = 0.038 and p = 0.022, respectively), swallowed larger boluses (p = 0.032), and had a significantly higher percentage of ineffective primary esophageal swallows (p = 0.0405). In addition, lick rate was significantly slower for old mice, measured using tongue cycle rate (p = 0.0034) and jaw cycle rate (p = 0.0020). This study provides novel evidence that otherwise healthy aging B6 mice indeed develop age-related changes in swallow function resembling presbyphagia in humans. Specifically, aging B6 mice have a generally slow swallow that spans all stages of swallowing: oral, pharyngeal, and esophageal. The next step is to build upon this foundational work by exploring the responsible mechanisms of presbyphagia in B6 mice.

Stress distribution in the temporo-mandibular joint discs during jaw closing: a high-resolution three-dimensional finite-element model analysis

This study aims at analysing the stresses distribution in the temporomandibular joint (TMJ) using a complete high-resolution finite element model (FE Model). This model is used here to analyse the stresses distribution in the discs during a closing jaw cycle. In the end, this model enables the prediction of the stress evolution in the TMJ disc submitted to various loadings induced by mandibular trauma, surgery or parafunction. The geometric data for the model were obtained from MRI and CT scans images of a healthy male patient. Surface and volume meshes were successively obtained using a 3D image segmentation software (AMIRA(®)). Bone components of skull and mandible, both of joint discs, temporomandibular capsules and ligaments and dental arches were meshed as separate bodies. The volume meshes were transferred to the FE analysis software (FORGE(®)). Material properties were assigned for each region. Boundary conditions for closing jaw simulations were represented by different load directions of jaws muscles. The von Mises stresses distribution in both joint discs during closing conditions was analyzed. The pattern of von Mises stresses in the TMJ discs is non-symmetric and changed continuously during jaw movement. Maximal stress is reached on the surface disc in areas in contact with others bodies. The three-dimension finite element model of masticatory system will make it possible to simulate different conditions that appear to be important in the cascade of events leading to joint damage.

Scaling of chew cycle duration in primates

The biomechanical determinants of the scaling of chew cycle duration are important components of models of primate feeding systems at all levels, from the neuromechanical to the ecological. Chew cycle durations were estimated in 35 species of primates and analyzed in conjunction with data on morphological variables of the feeding system estimating moment of inertia of the mandible and force production capacity of the chewing muscles. Data on scaling of primate chew cycle duration were compared with the predictions of simple pendulum and forced mass-spring system models of the feeding system. The gravity-driven pendulum model best predicts the observed cycle duration scaling but is rejected as biomechanically unrealistic. The forced mass-spring model predicts larger increases in chew cycle duration with size than observed, but provides reasonable predictions of cycle duration scaling. We hypothesize that intrinsic properties of the muscles predict spring-like behavior of the jaw elevator muscles during opening and fast close phases of the jaw cycle and that modulation of stiffness by the central nervous system leads to spring-like properties during the slow close/power stroke phase. Strepsirrhines show no predictable relationship between chew cycle duration and jaw length. Anthropoids have longer chew cycle durations than nonprimate mammals with similar mandible lengths, possibly due to their enlarged symphyses, which increase the moment of inertia of the mandible. Deviations from general scaling trends suggest that both scaling of the jaw muscles and the inertial properties of the mandible are important in determining the scaling of chew cycle duration in primates.

Kinematic analysis of an appetitive food-handling behavior: the functional morphology of Syrian hamster cheek pouches

Prodigious food hoarding in Syrian hamsters Mesocricetus auratus Waterhouse is strongly linked to appetite and is made possible by large internal cheek pouches. We provide a functional analysis of the cheek pouch and its associated retractor muscle. Frame-by-frame analysis of videotaped pouch-filling behavior revealed multiple jaw cycles for each food item pouched and the use of more jaw cycles to pouch large food items ( approximately 2.5 g chow pellets) than small (corn kernels or sunflower seed with husks). These results stand in contrast to previously reported pouching kinematics in the externally pouched Dipodomys deserti, which uses only one jaw cycle per pouching event. Comparison of pouching and mastication in the same individuals also suggests that in Syrian hamsters, feeding jaw cycles are modulated to accommodate pouch filling primarily by the addition of a pause between fast open and fast close phases, which we call ;gape phase'. Contrary to previous assertions, the retractor muscle does not merely provide structural support for the full pouch during locomotion. Video analysis of ten hamsters with unilaterally denervated retractor muscles and electrophysiological study of an anaesthetized subject confirmed that retractor muscle activity during pouch filling increases pouching efficiency for food items subsequent to the first.

An articulatory basis for the labial-to-coronal effect: /pata/ seems a more stable articulatory pattern than /tapa/

This paper investigates the coordination between the jaw, the tongue tip, and the lower lip during repetition with rate increase of labial-to-coronal (L(a)C(o)) consonant-vowel-consonant-vowel disyllables (e.g., /pata/) and coronal-to-labial (C(o)L(a)) ones (e.g., /tapa/) by French speakers. For the two types of disyllables: (1) the speeding process induces a shift from two jaw cycles per disyllable to a single cycle; (2) this shift modifies the coordination between the jaw and the constrictors, and (3) comes with a progression toward either a L(a)C(o) attractor [e.g., (/pata/ or /tapa/) --> /patá/ --> /ptá/] or a C(o)L(a) one (e.g., /pata/ or /tapa/ --> /tapá/ --> /tpá/). Yet, (4) the L(a)C(o) attractor is clearly favored regardless of the initial sequencing. These results are interpreted as evidence that a L(a)C(o) CVCV disyllable could be a more stable coordinative pattern for the lip-tongue-jaw motor system than a C(o)L(a) one. They are discussed in relation with the so-called LC effect that is the preference for L(a)C(o) associations rather than C(o)L(a) ones in CV.CV disyllables in both world languages and infants' first words.

Cyclic Motion of the Soft Palate in Feeding

The soft palate moves rhythmically during feeding, but the timing and frequency of this motion are not known. We tested the hypothesis that cyclic soft palate motion is temporally linked to cyclic jaw movement. Nine healthy, asymptomatic human subjects with normal dentition ate solid food coated with barium. Videofluorographic recordings showed that rhythmic motions of the soft palate during mastication were linked temporally to jaw motion. Soft palate motion occurred in every recording but not in every jaw cycle. The soft palate moved upward as the jaw opened, but the nasopharynx was not sealed. During swallowing, however, the soft palate invariably elevated during the intercuspal phase of jaw motion, sealing the nasopharynx. The frequency of soft palate cycles was lowest early in a feeding sequence and gradually increased as the sequence progressed from ingestion to swallowing. We conclude that cyclic movement of the soft palate in feeding is temporally linked to jaw motion.

Segment sequencing and the jaw cycle

The open–close jaw cycle established in running speech often spans the articulation of several segments. Moreover, the extremes of the cycle are associated with opposing segment types, consonants and vowels, which form higher-level linguistic units, syllables, when grouped. The present study sought to determine how the syllable is related to the cycle. A partial relationship may imply that the jaw moves linearly from one segment to another. An isomorphic relationship that jaw movement is planned over the articulation of a group of segments, regardless of segment sequencing within the group. Five speakers repeated one of five syllable types (CV, VC, CVC, CCV, VCC) continuously for several seconds, producing an unbroken sequence of consonants and vowels. Jaw movement and acoustic data were recorded simultaneously and used to determine the temporal boundaries of the cycles and syllables, respectively. Cycle boundaries were defined by the points of maximum closure preceding and following an opening gesture, and syllable boundaries according to changes in frequency and amplitude corresponding to the onset of the initial and final segments in the syllable. A comparison of the relative boundary locations suggested an isomorphic relationship between cycles and syllables that interacted with segment type, syllable shape, and speaker.

Correlation between intraoral pressures and tongue movements in the suckling pig

The objective was to clarify the relationship between tongue movements during suckling and the pressures in different parts of the oral cavity. A modified teat allowed a miniature pressure transducer to be passed through into the mouth. Intraoral pressures were recorded in piglets suckling on the teat attached (1) to a non-vented bottle or (2) to an automated milk delivery system. The movements of the tongue, of the milk and the transducer position were recorded by cine-radiography. In both modes of feeding, waves of elevation on the tongue moved in a pharyngeal direction and rose to contact the mid-posterior palate. Each wave corresponded to a jaw (suck) cycle in which milk was moved into and through the oral cavity. After each wave passed the transducer in the anterior part of the mouth, cyclical negative pressures were recorded. In bottle feeding, the intraoral pressure fluctuations (±2 mmHg) occurred against a background of a gradually developing negative pressure but, when feeding on the automatic delivery system, the same or smaller fluctuations occurred as changes from atmospheric pressure. Where the elevations contacted the mid-posterior palate in each cycle, a seal was formed (contact pressure >40 mmHg), so producing two functional antero-posterior compartments within the mouth; in these compartments pressures were generated independently. With the transducer in the valleculae, no general increase in pressure was recorded as milk accumulated there in each suck cycle but large positive pressures were recorded during the less frequent cycles when the vallecular space was emptied.

Functional morphology of the temporal region in the Rhynchocephalia

Study of the functional morphology of the temporal region of the Rhynchocephalia by means of the analysis of jaw musculature and bone structures in living lepidosaurians suggests that the streptostyly of the quadrate is a derived state in the Lepidosauria and that its origin may have been coupled with the loss of the M. pterygoideus atypicus. Further, this analysis supports the view that the retention of a fixed quadrate in early rhynchocephalians with an incomplete lower temporal bar may have been required for precise tooth occlusion and suggests that a solid lower temporal bar in later rhynchocephalians may have served as a brace to support the lateral side of the quadrate condyle and thus prevent it from twisting anteriorly rather than posteriorly during the jaw cycle. It is hypothesized that a common ancestor shared by the Rhynchocephalia and Squamata had a skull with an incomplete lower temporal bar but a rigid quadrate. It is also hypothesized that the presence of the anterior portion of the M. pterygoideus (MPT) is a primitive state, and that the size of the pterygoid flange may have been a good indicator of the presence of the anterior portion of the MPT in fossil reptiles. As in Sphenodon, if the mandible is able to move anteroposteriorly, it must retract first during the jaw cycle in those reptiles in which a pterygoid flange is retained.

Articulatory control of vowel length for contiguous jaw cycles: the effects of speaking rate and phonetic context.

The current study examined contiguous cycles of jaw movement in order to determine if select suprasegmental manipulations operate globally across the entire utterance, while phonetic changes are more locally administered. Specifically, articulatory kinematics were examined to determine if intra- and inter-articulatory spatial and temporal organization across manipulations of speaking rate was maintained for both jaw cycles while differing between the two cycles for phonetic changes (i.e., in coda composition) specific to the second jaw cycle. Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in the carrier phrase, "Now say again," using slow, normal, and fast speaking rates. Measures were made of the magnitude of jaw opening peak velocity and time to peak velocity, as well as of coarticulatory overlap and interarticulator timing, for the first jaw cycle (jaw lowering for /eI/ in "say" to the first /p/) and the second jaw cycle (jaw lowering for /ae/ to the second /p/). The current data indicate that, for intra-articulatory kinematics, the manipulation of phonetic context resulted in localized adjustments, whereas the manipulation of speaking rate was applied globally across the utterance. Conversely, for inter-articulatory kinematics, the upper lip-jaw synergy was reconfigured across the utterance for manipulations of speaking rate, whereas this synergy was maintained for localized manipulations in phonetic context. Results are discussed with respect to motor strategies being flexibly implemented as a result of contextual variation and speech rate.

Stability of intra- and inter-articulatory timing for contiguous jaw cycles

The current study compared how contiguous cycles of jaw movement, composed of different phonetic contexts, were impacted by global changes across the entire utterance and by more local, phonetic changes. Specifically, articulatory kinematics were examined to determine if patterns of intra- and inter-articulatory timing across manipulations of speaking rate were maintained for both jaw cycles, while being reorganized for phonetic changes (i.e., in coda composition) specific to the second jaw cycle. Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in the carrier phrase, ‘‘Now say —- again,’’ using slow, normal, and fast speaking rates. Changes in speaking rate impacted the utterance globally, with both jaw cycles evidencing similar patterns of kinematic change. Conversely, changes in coda composition for the second jaw cycle resulted in local changes to that cycle only, without impacting the first cycle. Individual speakers demonstrated distinct, but systematic patterns of intra- and interarticulatory timing as a function of coda composition and speaking rate. While functional groupings of articulators may be broken apart and reconfigured for subsequent movements, global suprasegmental changes result in timing patterns which are consistent across these reorganized functional groupings. [Work supported by CRDF–University of Pittsburgh and NSERC.]

Feeding kinematics ofphelsuma madagascariensis(Reptilia: gekkonidae): testing differences between iguania and scleroglossa

ABSTRACTThe kinematics of feeding in the gekkotan lizard Phelsuma madagascariensis (Scleroglossa) was investigated using high-speed cinematography (200–300 frames s−1 ) and X-ray films (64 frames s−1 ). Qualitative kinematic analysis of the head and jaw displacement of the prey to (capture) and within (reduction, transport, swallowing, licking) the buccal cavity are compared for two types of prey (crickets and mealworms) in 30 feeding sequences from four individuals. Maximal displacement of structures and timing of events are compared statistically to assess the differences among the phases and the prey using analysis of variance. P. madagascariensis uses its jaws only to capture the two types of prey item, and the capture jaw cycle is divided into fast-opening (FO), fast-closing (FC) and slow-closing (SC) stages only. As in iguanians and other scleroglossans, the reduction and transport cycles always involve a slow opening (SOI and SOII) stage before the FO stage, followed by FC and SC stages: this last stage was not easily identified in all feeding phase. Transport of the prey was followed by a large number of licking cycles. Our data show (i) that the capture profile in gekkotans is similar to that observed for other scleroglossans and different from that described for iguanians (e.g. the absence of an SO stage); (ii) that the kinematics of jaw and related hyo-lingual cycles of intraoral manipulation (reduction and transport) are similar in lizards with a very different hyo-lingual system (Iguania, Gekkota and Scincomorpha), suggesting a basic mechanism of feeding cycles in squamates, transformed in varanids and snakes; and (iii) that prey type affects the kinematics of capture and manipulation, although the high level of variation among lizards suggests a possible individual modulation of feeding mechanism. A principal components analysis was performed to compare capture and transport cycles in this study of P. madagascariensis (Gekkota) and a previous study of Oplurus cuvieri (Iguania). This analysis separated the capture cycle of each species, but the transport cycles were not completely separated. These results demonstrate the complexity of the modulation and evolution of feeding process in squamates.

The effect of food consistency upon jaw movement in the macaque: a cineradiographic study.

Variation in the form of masticatory cycles in individuals is often assumed to be limited. The contrary hypothesis, that jaw cycles vary widely but systematically with food consistency, was tested in macaques fed similarsized pieces of monkey chow, apple, and banana. With the animals under general anesthesia, radiopaque markers were inserted into the jaw, tongue, and hyoid. Oral movements were recorded by cineradiography at 100 frames/sec in lateral projection synchronously with frontal view cinephotography (50 frames/sec). The films were examined for the events that subdivide each jaw movement cycle into its constituent phases (fast closing, slow closing, intercuspal, slow or early opening, final opening). The frame numbers at which these events occurred were used to define phase durations. The numbers of cycles preceding a swallow increased with the hardness of the ingested food item. Regardless of the test food, every feeding sequence (initial ingestion to final clearance of mouth) contained multiple swallows, each of which defined the end of a sub-sequences when the animals were feeding on chow, the sub-sequences were initially long (20 cycles or more), but when they were feeding on banana, the sub-sequences were short (10 cycles or fewer). Although the form of individual cycles (defined by phase durations) was often unrelated to that of neighboring cycles, the general cycle characteristics in a sub-sequence typified a particular food. Chow feeding cycles were characterized by slow-closing (SC) phases of long duration with slow-opening (SO) phases of short duration; the characteristics of banana feeding cycles were the reverse. SC duration correlated directly and SO duration correlated inversely with food hardness (p < 0.001). The evidence supports the view that the centrally generated pattern of movement is highly dependent upon intra-oral sensory feedback.

Patterns of tongue and jaw movement in a cinefluorographic study of feeding in the macaque

Tongue movements in three female Macaca fascicularis, with radio-opaque markers in the tongue, teeth and hyoid, feeding on apple, banana and monkey chow, were recorded using lateral projection cineradiography (± 100 f.p.s.) with synchronized frontal view cinephotography (50 f.p.s.). Marker positions were digitized and the resultant Cartesian coordinates manipulated: (a) to establish the gape time profile; (b) anteroposterior and dorsoventral movements of tongue and hyoid markers relative to an upper occlusal/palatal reference plane; and (c) expansion and contraction of tongue segments in selected sections of complete sequences. The relative timing of tongue and jaw movement events was established using interval analysis. In simple transport cycles (semisolid food), all parts of the tongue moved in synchrony, travelling forwards and expanding during early opening, and backwards and contracting during late opening and closing. In contrast, in simple chewing cycles with a power stroke (SC phase): (a) the tongue markers reached their most backward position before or at the beginning of the SC phase, travelling forwards until the teeth approached intercuspation, then paused until after the teeth had reached centric occlusion; (b) the markers moved asynchronously, so that the relation between each marker and jaw movement changed; (c) expansion and contraction was largely confined to the middle tongue segment. In complex chewing cycles, jaw movement in opening was linked to the behaviour of the anterior tongue segment: reversal from forward to backward movement of the anterior tongue marker occurred within 30 ms of the rate change at the SO (slow open)-FO (fast open) transition: the greater the amplitude of forward movement, the longer the SO phase. Hyoid (tongue base) movement occurred throughout masticatory sequences. A backward drift of the hyoid and posterior part of the tongue occurred in cycles preceding swallows. Linkages between tongue and jaw movements in feeding in macaques are more complex than those reported for non-primate mammals, as they change between successive jaw cycles. The changes observed during sequences, and between different foods, suggest that the effector systems involved are continuously modulated, and the jaw-movement profile during opening may be dependent on the pattern of tongue movement.

The electromyographic activities of jaw and hyoid musculature in different ingestive behaviours in the cat

Electromyographic (EMG) activity in the muscles moving the jaw, hyoid and tongue of the cat was recorded during the intake of solid and liquid foods; the nature of the movements of the jaw, hyoid, tongue and food were recorded and identified cineradiographically. Synergy was evident in muscles with similar anatomical orientation. However, most muscles were activated more than once during each jaw cycle and some of these additional periods of activation occurred at times not predicted by the anatomical arrangement of the muscles. The pattern of EMG activity was the same during all lapping cycles (excluding lap/swallow cycles) but was characteristically different from that occurring during the ingestion of solid food. With solid food the EMG pattern changed during the course of the ingestive sequence and was characteristic for each of the four successively different types of jaw cycle, i.e. transport cycles moving food back from the front of the mouth to the cheek teeth, chewing cycles, transport cycles moving food through the fauces and, following the accumulation of a bolus in the vallecula, swallowing cycles. In these data, provided that the EMG activities of a complete ingestive sequence were available (from food pick-up to swallow), the cycle type could be identified from the intracycle timings and amplitudes of the bursts of EMG activity occurring in the fibres of temporal, posterior digastric and geniohyoid muscles alone. Two variable components of the cyclical EMG pattern could be identified, one relating to tongue movement, the other to jaw movement.

Kinematics of Feeding Behaviour in Oplurus Cuvieri (Reptilia: Iguanidae)

ABSTRACT The kinematics of prey capture, reduction and transport to the oesophagus by the iguanian lizard Oplurus cuvieri were investigated using high-speed cinematography (100-200 frames s∼’) and cineradiography (60 frames s’1). Thirty feeding sequences from four individuals were analysed. Feeding sequences were divided into four phases: capture, reduction, transport to the oesophagus and cleaning. Quantified kinematic profiles of the head, jaws, hyoid-tongue complex and displacements of the prey to (capture) and within (other phases) the buccal cavity are presented from cinematographic frames. Twenty additional variables, depicting maximal displacements and the timing of events, were calculated from the profiles. Variables documenting gape cycles were used in a first principal component analysis for studying the kinematic relationships between the phases. Markers were placed in the tongue of two individuals for cineradiographic study to illustrate displacements of the tongue. During prey capture, the jaw cycle is divided into slow opening (SO I and SO II), fast opening (FO) and fast closing (FC) stages. During the reduction phase, jaw cycles do not always involve an SO stage and the first reduction cycle never exhibits an SO stage. During transport, the duration of the SO stages is highly variable. During reduction and transport of the prey, the cyclic tongue movements are very similar. Gape opening during cleaning is not divided into two successive stages. We conclude (1) that the capture, reduction and cleaning cycles may be derived from the transport cycle, (2) that the SO stage is determined by tongue displacements in all the phases, (3) that, in the extensive intraoral food processing, related cyclic tongue-jaw displacements are not different, (4) that gape cycles do not always follow the Bramble and Wake model, and (5) that the evolutionary features proposed for Amniota by Reilly and Lauder are present.

Different phase-stable relationships of the upper lip and jaw for production of vowels and diphthongs

Relational invariants have been reported in the timing of articulatory gestures across suprasegmental changes, such as rate and stress. In the current study, the relative timing of the upper lip and jaw was investigated across changes in both suprasegmental and segmental characteristics of speech. The onset of upper lip movement relative to the vowel-to-vowel jaw cycle during intervocalic bilabial production was represented as a phase angle, and analyzed across changes in stress, vowel height, and vowel/diphthong identity. Results indicated that the relative timing of the upper lip and jaw varied systematically with changes in stress and vowel/diphthong identity, while remaining constant across changes in vowel height. It appears that modifications in relative timing may be due to adjustments in the jaw cycle as a result of the compound nature of jaw movement for diphthongs as compared to vowels, with further modifications due to the effect of stress on these compound movements.