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A kinematic description of the temporal characteristics of jaw motion for early chewing: Preliminary findings

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Purpose: The purpose of this investigation was to describe age-and consistency-related changes in the temporal characteristics of chewing in typically developing children between the ages of 4 and 35 months and adults using high-resolution optically
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  University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Special Education and Communication DisordersFaculty PublicationsDepartment of Special Education andCommunication Disorders1-1-2012  A Kinematic Description of the TemporalCharacteristics of Jaw Motion for Early Chewing:Preliminary Findings Erin M. Wilson University of Wisconsin-Madison  , emhillman@wisc.edu  Jordan R. Green University of Nebraska-Lincoln  , jgreen4@unl.edu Gary Weismer University of Wisconsin - Madison  , gweismer@wisc.edu Follow this and additional works at:hp://digitalcommons.unl.edu/specedfacpubPart of theSpecial Education and Teaching Commons is Article is brought to you for free and open access by the Department of Special Education and Communication Disorders atDigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Special Education and Communication Disorders Faculty Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.  Wilson, Erin M.; Green, Jordan R.; and Weismer, Gary, "A Kinematic Description of the Temporal Characteristics of Jaw Motion forEarly Chewing: Preliminary Findings" (2012). Special Education and Communication Disorders Faculty Publications. Paper 71.hp://digitalcommons.unl.edu/specedfacpub/71  S uccessful oral feeding depends on the temporal co-ordination of multiple oral and pharyngeal struc-tures. The coordination for suckling, one of theearliest-appearing oral-feeding behaviors, seems to berelatively well established at birth (Finan & Barlow,1998). For example, Bosma (1986) described oral andpharyngeal movements during the early stages of suck-ling development as already rhythmic, a suggestion that has been conrmed by a number of investigators (Arvedson, Rogers, & Brodsky, 1993; Morris & Klein,2000). Morris and Klein suggest that “rhythm is themost consistent characteristic of feeding patterns during the rst 3 months of life” (2000, p. 67). These descrip -tions might be interpreted to suggest that the basic tem-poral organization of feeding patterns is relatively wellestablished in early infancy.Although the basic rhythmical structure of oralmovements during feeding may be well establishedduring infancy, empirically derived knowledge aboutthe development of mandibular control for early chew-ing is very limited. To date, only a small number ofquantitative studies have been conducted (Ahlgren, 1966; Gisel, 1988, 1991; Green et al., 1997; Schwaab, Ni - man, & Gisel, 1986; Schwartz, Niman, & Gisel, 1984;Steeve, Moore, Green, Reilly, & Ruark McMurtrey, 2008), and even fewer investigations have targetedchewing at its earliest developmental stages (Gisel, 1991; Steeve et al., 2008; Steeve & Moore, 2009; Wil -son & Green, 2009). Moreover, many of these studieshave not accounted for the developmental progres-sion in food consistency (i.e., progression from soft to hard food); in contrast, the signicant effects of bo -lus consistency on chewing rate is well documentedin the adult literature (Anderson, Throckmorton, Bus-chang, & Hayasaki, 2002; Arizumi, 1989; Filipic & Ke-ros, 2002; Horio & Kawamura, 1989; Karkazis, 2002; Published in  Journal of Speech, Language, and Hearing Research 55 (April 2012), pp. 626–638; doi:10.1044/1092-4388(2011/10-0236)Copyright © 2012 American Speech-Language-Hearing Association. Used by permission.Submitted August 26, 2010, revised February 4, 2011; accepted August 30, 2011; published online January 5, 2012. A Kinematic Description of the Temporal Characteristicsof Jaw Motion for Early Chewing:Preliminary Findings Erin M. Wilson, 1 Jordan R. Green, 2 and Gary Weismer 3   1. Waisman Center, University of Wisconsin—Madison2. University of Nebraska—Lincoln3. University of Wisconsin—Madison Corresponding author  — Erin M. Wilson,emhillman@wisc.edu Abstract Purpose: The purpose of this investigation was to describe age- and consistency-related changes in the temporal characteristics of chewing in typically developing children between the ages of 4 and 35 months and adults using high-resolution optically basedmotion capture technology. Method: Data were collected from 60 participants (48 children, 12 adults) across 5 age ranges (beginners, 7 months, 12 months, 35months, and adults); each age group included 12 participants. Three different food consistencies were trialed as appropriate. Thedata were analyzed to assess changes in chewing rate, chewing sequence duration, and estimated number of chewing cycles. Results: The results revealed both age- and consistency-related changes in chewing rate, sequence duration, and estimated num-ber of chewing cycles, with consistency differences affecting masticatory timing in children as young as 7 months of age. Chew-ing rate varied as a function of age and consistency, and chewing sequence duration was shorter for adults than for children re-gardless of consistency type. In addition, the results from the estimated number of chewing cycles measure suggest that chewingeffectiveness increased with age; this measure was also dependent on consistency type. Conclusions: The ndings suggest that the different temporal chewing variables follow distinct developmental trajectories and are consistency dependent in children as young as 7 months of age. Clinical implications are detailed. Keywords: chewing, kinematics, development, consistency, timing 626  K inematic D escription   of   the t emporal c haracteristics   of J aw m otion   for e arly c hewing 627 Karkazis & Kossioni, 1997, 1998; Lundeen & Gibbs,1982; Mioche & Peyron, 1995; Peyron & Mioche, 1994;Peyron, Mioche, & Culioli, 1994; Peyron, Mioche, Re - non, & Abouelkaram, 1996; Steiner, Michman, & Lit - man, 1974). Gisel and colleagues reported that chewing timing is also affected by bolus consistency in children (Gisel, 1988; Schwaab et al., 1986; Schwartz et al., 1984) even as young as 6 months of age (Gisel, 1991). There-fore, an improved understanding of chewing devel- opment will require consistency-specic descriptions of age-related changes in mandibular control. Ideally,these descriptions will begin with the earliest stagesof chewing to describe the transition from primitivemunching to mature chewing (Morris & Klein, 2000). Chewing Rate The frequency of jaw oscillation during chewing (i.e.,chewing rate) is one of the few variables that has beenstudied during development (Ahlgren, 1966; Gisel, 1988; Green et al., 1997; Schwaab et al., 1986; Schwartzet al., 1984; Sheppard & Mysak, 1984; Steeve et al.,2008). The ndings from this research for both children and adults are summarized in Table 1. Despite differ-ences across investigations in participant ages, bolus consistencies, and methodologies, the ndings are re -markably similar, suggesting that variation in chew- ing rate across age is relatively small. Will kinematic representations of chewing-like behavior yield similarresults? Chewing Sequence Duration Chewing sequence duration is commonly reported inthe pediatric literature and provides normative infor-mation about the amount of time required to manipu-late a bolus in preparation for swallow; however, the ndings from studies on age-related changes in the du -ration of chewing sequences (i.e., the amount of timerequired to break down a bolus) have been mixed. Sheppard and Mysak (1984) observed an increase inchewing duration with age in young infants (age ≤35 weeks), whereas Gisel and colleagues reported a de-crease in chewing duration in children from 6 monthsto 2 years of age (Gisel, 1991), from 2 to 5 years of age (Schwaab et al., 1986), and from 2 to 8 years of age(Gisel, 1988); however, there was no signicant differ - ence in chewing duration in children between 4 and 5years of age (Schwartz et al., 1984). Chewing Effectiveness Temporal measures of chewing have also been usedto document changes in chewing effectiveness withage. For example, Gisel (1988, 1991) reported a de-crease in both the chewing sequence duration and thenumber of chewing cycles required to chew and swal-low a bolus. Results from other investigations, how- ever, suggest that age does not inuence measures ofchewing effectiveness at certain age intervals (Schwaabet al., 1986; Schwartz et al., 1984). Electromyographic studies of mandibular muscle activation patterns haveprovided perhaps the strongest evidence of increased chewing effectiveness with age (Green et al., 1997;Steeve et al., 2008). For example, older children ex -hibit the same chewing frequency as younger childrenbut with shorter bursts of muscle activity (Green et al., 1997). Relevance to Current Models of Feeding Development: The Role of Central PatternPenerators The oral motor coordination for chewing develops in the context of signicant neurologic, neuromotor, and anatomic change. Therefore, kinematic-based observa-tions have the potential to provide new insights intothe driving forces for change and/or behavioral sta-bility in chewing performance across age. Many ofthe current models of feeding assign a primary role tobrainstem central pattern generators (CPGs) for regu-lating coordination among oral muscles for early suck- ing and chewing (Agrawal & Lucas, 2002; Barlow &Estep, 2006; Dellow & Lund, 1971; Finan & Barlow,1996, 1998; Lund, 1991; Lund, Appenteng, & Seguin,1982; Lund & Kolta, 2006). The CPG, which has beenconrmed in nonhuman animal models, acts as an in -ternal rhythm regulator and is affected by both periph-eral and central input. The CPG sends alternating acti-vation signals to antagonistic muscle pairs to producethe rhythmic jaw-opening and -closing pattern char- acteristic of chewing (Agrawal & Lucas, 2002; Lund,1991). The observation of signicant developmental change in the temporal characteristics of chewing pat- Table 1. Chewing rates from previous investigations.Age group Lead author (year) Chewing rateAdults Möller (1966) 1.46–1.73 HzAdults Steiner et al. (1974) 0.60–1.80 HzChildren Ahlgren (1966) 1.73 HzChildren Schwartz 0.8 ± 0.2–et al. (1984) 1.3 ± 0.5 s/cycleChildren Sheppardand Mysak (1984) 0.36–1.1 HzChildren Schwaab (1986) 0.62–1.25 HzChildren Gisel (1988) 0.71–1.25 HzChildren Green (1997) 0.88–2.11 Hz(12–38 months)Children (9 months) Steeve (2008) 1.23–1.99 Hz  628 w ilson , g reen , & w eismer   in    J  ournal   of  S peech   , l  anguage  ,  and h  earing r eSearch  55 (2012)   terns may provide a better understanding of how CPGmechanisms are gradually tuned through experience to accommodate signicant developmental changes in chewing anatomy and neuromuscular function. Alter-natively, the observation that chewing rate does notchange with age might be interpreted to support therobust nature of the masticatory CPG, because, for ex-ample, the rate of chewing might be expected to de-crease with age as mandibular structures become moremassive with growth. Relevance to Current TherapeuticApproaches Some clinical descriptions of disordered feeding have noted irregularities in the temporal characteristics ofchewing movements. Consequently, certain early feed-ing therapies have focused on facilitating the rhythmic-ity, for example, of early feeding movements (Morris &Klein, 2000). Because many aspects of chewing coordi-nation change with age, quantitative information aboutthe temporal aspects of early chewing development isneeded to establish (a) empirically sound benchmarksfor gauging the presence and severity of early feedingdisorders and (b) developmentally appropriate thera-peutic goals.  Purpose A more current account of the development of temporalcharacteristics for chewing is warranted with the recentadvent of methods for noninvasively tracking jaw mo-tion in young children. The aim of this investigation wasto describe age-related changes in the temporal charac-teristics of chewing in typically developing children be- tween the ages of 4 and 35 months and in adults using high-resolution, optically based motion capture tech-nology. The following three aspects of chewing timingwere investigated cross-sectionally: (a) chewing rate, (b)chewing sequence duration, and (c) estimated numberof chewing cycles. The effects of consistency on the age-related changes of these variables were also examined.  Method  Participants The investigational protocol was approved by the Uni- versity of Wisconsin’s Institutional Review Board. Fol -lowing approval, data were collected from 60 partic- ipants (48 children, 12 adults) across ve age ranges(beginners, 7 months, 12 months, 35 months, and adults); each age group included 12 participants. The age ranges were selected to reect documented stages in the development of mastication (Arvedson, 1993; Arvedson & Lefton-Greif, 1996; Arvedson et al., 1993; Bosma, 1986; Morris & Klein, 2000; Pinder & Faherty, 1999; Pridham, 1990; Sheppard & Mysak, 1984). Morespecically, ndings from this literature suggest that at7 months of age, the chewing pattern is emerging; at 12 months of age, the basic chewing pattern has been es-tablished; and at 35 months, the basic chewing pattern has become considerably rened. Because parents in -troduce spoon-feeding at a variety of ages, the “begin- ner” age group comprised children ranging from 4 to 6 months of age, all of whom had approximately 2 weeksof experience with foodstuff prior to the data collectionsession. It is during this beginner age range that chew-ing is a novel behavior, and the basic chewing pattern istypically not well established. The data from the adultsubjects provided a theoretical end point for jaw perfor-mance during chewing.Participants were judged to be typically developingbased on (a) an informal developmental questionnaireadministered during an initial telephone call and (b) use of the Ages & Stages Questionnaire (ASQ)—Second Edi - tion (Squires & Bricker, 1999), which is a parental reportscreener that assesses development across ve domains,including ne- and gross-motor control, communica -tion, problem-solving, and personal-social skills. Par- ents were asked to complete the ASQ within one month of completing the data collection session and approxi-mately six months after the session to ensure the partic-ipants continued to demonstrate typical development.Data from one beginner participant were excluded fromthe data corpus because of a developmental delay that was identied within six months of participating. Materials and Procedure Three-dimensional motion capture system. Adults wereseated in a chair, and child participants were placedin an infant seat on a chair and secured with lap andshoulder straps. Data were collected using a three-di-mensional motion capture system (Vicon, 250). The sys- tem consisted of ve cameras that registered jaw motion at 60 frames per second and a computer workstation that used the ve cameras to derive the three-dimen -sional position of markers strategically located on thechin during chewing.  Marker system. The small reective markers (approx -imately two millimeters) were placed on seven faciallandmarks. One marker was placed on the gnathion(JC), two were placed 2 cm to the right (JR) and left of the gnathion (JL), and a marker array was placed on the forehead (see Figure 1). The forehead marker array de- ned an anatomically based coordinate system (Wilson & Green, 2009). Although three markers were placedon the chin to ensure optimal tracking, movement fromonly one chin marker per chewing trial was selected for  K inematic D escription   of   the t emporal c haracteristics   of J aw m otion   for e arly c hewing 629 analysis. Whenever possible, the JL or JR markers were selected for analysis because movement of the markersto the right and left of the gnathion more accurately rep- resent motion of the mandible (Green, Wilson, Wang,& Moore, 2007). However, timing is well preserved re -gardless of which marker is selected (Chmielewski, Feine, Maskawi, & Lund, 1994; Green et al., 2007; Hägg - man-Henrikson, Eriksson, Nordh, & Zafar, 1998; Jemt &Hedgård, 1982; Zafar, Nordh, & Eriksson, 2002). Food. Food was provided by the family or investi-gators. Because food selections and consistencies were based on each child’s typical diet, we were unable toadminister the same foodstuff to each participant. Wetherefore required that the food t into three different food consistency categories:  puree,   semisolid, and solid . Consistency classication was carefully judged by the primary investigator and was based on the criteria of the National Dysphagia Diet (2002). Because the abil -ity to manage different consistencies is a learned behav-ior, the participants were asked to trial each consistencyonly if they had approximately two weeks of experience with a specic consistency classication. The beginner age group, therefore, was only capable of trialing a pu-ree-consistency food. The caregivers and/or primary in-vestigator fed each child, and the size of each food bitewas consistent across trials and participants (i.e., 1 tea-spoon). The adult participants fed themselves, but bolussize was the same as for the children, and administra-tion was closely monitored by the primary investigator. As appropriate, attempts were made to administer ve trials of each consistency type to every participant, al-though because of developmental level and/or compli- ance, not every participant accepted all ve trials (seeTables 3 & 4).  Missing data. Missing data occurred if the marker wasnot captured in view of at least two cameras. Data were only included in the nal data corpus if at least 75% of the chewing sequence was present for one of the jaw markers; 7.01% (37/528) of the sequences in the nalcorpus had <25% missing data. To maximize the yieldfrom the data set for the rate analysis, each le with missing data was further parsed to include the greatestportion of continuous data while excluding the missingsegment; however, only complete sequences were an-alyzed for the measures of chewing sequence durationand estimated number of chewing cycles. Finally, a re-quirement that each chewing sequence had to contain atleast 1.5 cycles of chewing (i.e., jaw at minimal displace-ment, maximum displacement, minimum displacement,and maximum displacement) was established. This cri-terion was established to ensure that all sequences con-tained actual chewing motion because participants wereoccasionally observed to almost immediately swallow certain consistency boluses. Sixty-one trials were ex -cluded as a result of this criterion (see Table 2). Data editing. Movement data were parsed into chew-ing sequences based on the continuous digital video re-cordings. A chewing sequence began at the point ofmaximal jaw closure after  the spoon had been removedfrom the mouth and ended approximately at the point Figure 1. Marker array. Panel A: Marker placement on infant. Panel B: Corresponding marker representation in three-dimensionalspace.
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