EMGofArticulatoryMuscles Technique

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Electromyography of the Articulatory Muscles:Current Instrumentation and TechniqueHaj ime Hirose*Haskins Laboratories, New Haven

The part icular merit of electromyography (EMG) in speech research istha t i t can provide information about the speech gesture in i t s natural unitsand that i t d ~ r e c t l y ref lec ts the motor command from the central nervoussystem carried by neural impulses. Recent technical developments in EMG havemade possible examination of the art icula tory muscles without affecting naturalspeech performance. The present report describes a current technique used a tHaskins Laboratories for the assessment of ~ 1 G data from the human art iculatorymuscles.

ELECTRODESAt present, hooked-wire electrodes are used exclusively. The wire currently in use i s a platinum-iridium alloy (90%-10%) with polyester (Isonel)coating, the diameter of which is 0.002 in . (Consolidated Reactive M etals,P-91). This wire is ideal for these experimental purposes, since i t is lesseas i ly crimped or bent than copper wire and less springy than sta inless s tee l .

In addit ion, the wire i s possibly less i r r i t a t ive to human t i ssues than areother kinds of metal since no chemical reaction is to be expected.The electrodes are made in essent ia l ly the same way as described byprevious authors (Hirano and Ohala, 1969; Basmajian and Stecko, 1962). Aftera wire tha t i s long enough to serve as a pair 6f electrodes (50-60 em forpercutaneous inser t ion and 80-90 em for peroral insert ion) has been prepared,the two free ends are threaded into the t ip of a hypodermic needle (26 or 27

gauge and 3/4 to 2 in . in length) and pulled through the needle un t i l a smallloop remains. The loop is bent and cut with a razor blade to leave two shorthooks of approximately 1-2 mm a t the t ip of the needle. Care is taken to makethe two hooks of different lengths so as to avoid a possible short ci rcui t bycontact of the two cut ends in the muscle. The other ends of the.wire areburned in a match flame to remove the polyester coating for connection to apreamplifier of the recording system.

For peroral insert ion into the v ~ l o p h a r y n g e a l muscles, the shaft of anelectrode-bearing needle can be angulated to allow easier access to thetarget muscles.For EMG of some laryngeal muscles, a specially designed probe is usedfor peroral inser t ion by indirec t laryngoscopy. The probe consis ts of an

L-shaped metal rod and the shaf t of a 26-gauge needle cut and epoxy-bonded tothe end of the shorter arm of the rod. The hooked-wire electrodes are madeby threading the wire through the car r ier needle in the conventional mannerand also through a thin polyethylene tube bonded along the rod (Figure 1).*Also Faculty of Medicine, University of Tokyo. 73


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-...1-"'"

11~ .

An 1-shaped Probe Used for Peroral Insert ion of the Hooked-Wire Electrodesinto the Posterior Cricoarytenoid and th e Interarytenoid

Note: The shaft of a 26-gauge hypodermic needle i s epoxy-bonded to the shorterarm.


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The advantages and disadvantages of hooked-wire electrodes have beendiscussed so ful ly by previous authors (Hirano and Ohala, 1969; Harris , 1970)tha t no fur ther comment wil l be made in the present report .

GENERAL PROCEDURESSter i l iza t ion of the needle and the wire electrodes is accomplishede i the r by high-pressure heat or by ant isept ic solut ions.Before each experiment , i f i t is deemed necessary to inhibi t sa l iva t ion,

7-10 drops of Tincture of Belladonna i s administered by mouth. For peroralinser t ion of the electrode s, top ical anesthesia i s administered to the pharynxusing Cetacaine 1 spray and to the larynx, by th is same method, in the case oflaryngeal EMG. This i s followed by a gargle or ins t i l l a t ion of 2-3 ml of 2%Xylocaine.2 The percutaneous insert ions are preceded by topical administrat ionof 2% Xylocaine without epinephrin through a Panjet-70 air j e t (Panray)3 at thes i te of the needle inser t ion.

The skin i s disinfected at the s i te of inser t ion with an alcohol swab. Aground electrode (a gold earring) is at tached to the ear lobe of the subject .During electrode inser t ion, an osci l loscope and an amplif ier-speaker systemare used for monitoring the pert inent muscle act iv i ty . After inser t ion intoan appropriate s i t e , the electrode-bearing needle i s withdrawn leaving theelectrodes hooked in the ta rget muscle.

Whatever posi t ion i s taken during electrode placement and i t s ver i f ica t ion,the data recording i s made with the subject in an upright s i t t ing posi t ion.Oscilloscopic monitoring of selected EMG channels i s provided throughoutthe procedure.

INSERTION TECHNIQUES AND VERIFICATION OF ELECTRODE PLACEHENTCorrect placement of the electrodes in the target muscle is prerequisi teto the entire experimental procedure in an EMG study. The exact placement

of the electrodes is eas ier i f (1 ) the ta rget muscle is close to or imme-dia te ly beneath the covering skin or the mucosa and the insert ion i s possibleunder direct inspect ion or (2) there i s l i t t l e poss ibi l i ty of contaminationwith other muscles. In any case, ver i f ica t ion of electrode placement i sabsolutely necessary.

1cetacaine (trade name) is packaged in a 50-ml aerosol bot t le and containsthe fol lowing: ethyl aminobenzoate, 14%; butylamino-benzoate, 2%; benzalkonium chlor ide, 0.5%; cetyldimethylethyl ammonium bromide, 0.005%. A onesecond spray releases 0.1 ml of so lu t ion , an d usually three to four secondsof spray are needed to anesthet ize the oral and pharyngeal mucosa. (Gaskilan d Gil l ies , 1966).2Recent s tudies (Shipp, 1968; Zemlin, 1969) revealed no discernible ef fec tof topical anesthesia on normal laryngeal behavior.3ranjet -70 delivers approximately 0.1 ml of the anesthet ic solut ion to c i r -cumscribed intradermal depth up to 6 mm penetrat ion.

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In principle , correct placement of the electrodes i s verif ied bymonitoring the muscle act iv i ty induced by appropriate gestures that havebeen considered pert inent for the contraction of the target muscle. Fo rsome ar t icula tory muscles, however, there i s a lack of normative EMG dataon which our ver i f ica t ion ca n rely, as Shipp et a l . (1968) have pointed out.Verificat ion thus depends to a cer ta in extent on the experimenter 's empiricaljudgment based on his knowledge of anatomy and c l in ica l and experimentalpract ice . Further effor t wil l be needed to reach unanimous agreement on thenormative behavior of the art iculatory muscles, although some interindividualvar ia t ion both in anatomy and in function must always be taken into consideratioIns t r ins ic laryngeal muscles

Poster ior cricoarytenoid (PCA). The PCA is reached perorally by indirectlaryngoscopy using the L-shaped needle holder described above. Using th isapproach, one can inser t the needle para l le l to the alignment of the musclef ibers; insert ion i s performed under inspection with a laryngeal mirror.During insertion, the subject i s in a s i t t ing posi t ion and i s asked to phonatea sustained vowel so as to open his hypopharyngeal lumen for easier access tothe s i te of inser t ion, which i s i l lus t ra ted in Figure 2. The insert ion i sthus made into the belly of the muscle on the cricoid cart i lage through thehypopharyngeal mucosa. By th is approach, there is l i t t l e possibi l i ty of contamination with neighboring muscles unless the insert ion i s made to o crania l ly .

Identif ication i s made by having the subject repeat short periods ofvowel phonation interspersed with deep inspiration. The PCA i s act ive forinspiration and suppressed for the period of phonation, and this pattern i svery characterist ic .

Interarytenoid (INT). The inser t ion into the INT can be made ei therperorally or percutaneously. For peroral approach, the same technique i sused as for the PCA and inser t ion is made a t the midline between the twoarytenoid prominences (Figures 3 and 4). By the percutaneous route, thetransporting needle is inserted through the cricothyroid space, penetratingthe skin and the cricothyroid membrane at the midline. Under inspection witha laryngeal mirror, the needle i s pushed backwards and sl ight ly upwards so asto pierce the anterior wall of the interarytenoid region to reach the INT(Figures 3 and 4). Both approaches are made with the subject in a s i t t ingposi t ion. There i s almost no possibi l i ty of contamination with other musclesin this case.

Verification of the placement i s made by asking the subject to repeatshort periods of phonation. The general pattern of INT act iv i ty is almostreciprocal to PCA; there is marked act iv i ty for the period of phonation.Cricothyroid (CT). The percutanous route is always taken with thesubject in a supine posi t ion. Insert ion is made at a point above the cricoidring and approximately 1 em l a t e ra l to the midline. The needle i s directedposterolaterally and sl ight ly upwards aiming a t the lower edge of the thyroid

lamina. This i s the same technique as reported by Hirano and Ohala (1969).Verification of the correct placement is made by asking the subject toattempt an ascending scale. The CT shows marked act iv i ty for a quick r isein fundamental frequency.

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A Diagrammatic View of the Larynx During Sustained Phonation byIndirect Laryngoscopy

Fig.2

Note: A cross (x) indicates one point of needle inser t ion into the posteriorcricoarytenoid

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A Sagit tal Section of the Larynx with I l lus t rat ion of the Direction ofNeedle Inser tion to the Interarytenoid

B.

~ - - - - 1 1 - interorytenoid

A.

A. Percutaneous RouteB. Peroral Route

Fig. 3


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Indirect Laryngoscopic View of the Larynx During Quiet Respiration

Note: An arrow ( ~ ) indicates the direction of a needle inser ted percutaneouslyinto the subglotta l space towards the interarytenoid area. A cross (x)indicates one point of needle inser tion into the interarytenoid by theperoral route.

Fig.4

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There i s , however, a possibi l i ty of misplacement of the electrodesei ther in the l a t e ra l cricoarytenoid (LCA) i f the placement is too deep orin the sternohyoid (SH) i f the inser t ion is too superf ic ia l . In order todifferent ia te the CT from the LCA, the subject is asked to attempt breathholding or swallowing. These maneuvers should not give EMG act iv i ty unlessthe placement is into the LCA. For discrimination from the SH, the subjectis then asked ei ther to open his jaw by resist ing the experimenter 's handholding it or to ra ise his head from the headrest . These attempts wil le l ic i t marked act iv i ty i f the inser t ion is not deep enough and the electrodesare hooked into the SH.

Thyroarytenoid (VOC). Percutaneous inser t ion is made with the subjectin a supine posit ion attempting sustained phonation. The skin is pierced a ta point close to the midline a t the level of the cricothyroid space. Theneedle i s then directed cranial ly and sl ight ly la teral ly penetrating thecricothyroid membrane to reach the muscle from i t s infer ior surface (Figure 5).This route is s l ight ly dif fe rent from that reported by Hirano and Ohala (1969),since the needle does not pass through the subglot tal space but through thesubmucous t issues near the anter ior commissure.

For veri f icat ion, the subject attempts to produce low-frequency phonation.The VOC also shows act iv i ty during swallowing. Although there is l i t t l epossibi l i ty of contamination with other muscles, the electrodes can pick upthe mechanical vibration of the vocal fold i f the placement is made to oclose to the f ree margin of the fold. In such a case, replacement of theelectrode by another inser t ion is mandatory.

Lateral cricoarytenoid (LCA). The point of insert ion is almost thesame as for the CT. The needle is then directed la teral ly and sl ight lycrania l ly penetrating the cricothyroid membrane at a point anter ior to theinferior tuberculum of the thyroid cart i lage and deeply enough to reach theLCA. This route is similar to that reported by Hirano and Ohala (1969). (SeeFigure 5.) Contamination with the VOC can be avoided i f the direction ofinser t ion is kept l a t e ra l and less cranial so as to stay along the contourof the cr icoid r ing.

Ident if icat ion is made by having the subject attempt breath-holdingor glo t t a l stop production. These maneuvers, as well as swallowing, givemarked act iv i ty and serve to discriminate the LCA from the CT as describedabove.Strap Muscles of the Neck

Sternohyoid (SH). The contour of the SH can be palpated or even seenthrough the skin when the subject is asked to raise his head from the headres t in supine posi t ion with his head kept extended, unless the subject hasa very shor t , fa t neck. The contour is usually clear a t the level of thethyroid lamina where the insert ion i s made. This region is also preferrableto avoid possible contamination with other muscles. As the subject raiseshis head in a supine posi t ion, the needle is inserted l a t e ra l to the midlinepara l le l to the alignment of the muscle f ibers . This technique is similarto that reported by previous authors (Hirano et a l . , 1967).

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Ct:l1-'

A View of th e Larynx with the Right Thyroid Ala Removed

posteriorcricoarytenoidlateralcricoarytenoid

thyroarytenoid

B.

Fig. 5Note: Arrows indicate th e direc t ion of needle inser t ion into the thyroarytenoid (A) and intothe l a tera l cricoarytenoid (B). (This f igure is a modification of Hirano. and Ohala,Fig. 6, 1969.)


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The exact placement is verif ied i f marked act iv i ty i s observed whenthe subject ra ises his head from the supine posi t ion, opens his jaw, orproduces very low-frequency phonation.Sternothyroid (ST). The ST i s covered by the SH for almost i t s ent i recourse in the neck except for the most caudal port ion, where i t tends torun more medially than the SH, since the ST at taches to the sternum more

medially than the SH, as i l lus t ra ted in standard textbooks of anatomy.Therefore, ou r attempt a t reaching th is muscle i s made by insert ing theneedle at a level 2-3 em above the suprasternal notch and a t the anter iorborder of the sternomastoid muscle and by directing the needle crania- la tera l ly .

When the subject contracts th is muscle by holding his head up from the headre s t in a supine posit ion, we usually fee l penetration of i t s fascia followedby marked EMG act iv i ty observed on a monitor oscilloscope. The gross patternof act iv i ty of the ST i s not much dif ferent from that of the SH so thatabsolute discrimination from the SH may s t i l l be questionable, although i ti s claimed that the ST appears to be more relevant for pitch lowering thanthe SH (Simada e t a l . , in press; Hirano, pers . com.).

Thyrohyoid (TH). The TH runs direc t ly on the thyroid lamina and attachesto the l inea obliqua, where i t is covered by other strap muscles. Insert ionof the needle i s made at the level of the superior edge of the thyroid lamina,and the needle is pushed caudally and l a te ra l ly aiming a t the l inea obliquaunt i l the t ip of the needle hi t s the surface of the car t i lage . The cut endsof the electrodes should then be placed in the muscle t issue of the TH, sincethere is some distance between the hooked ends of the electrodes and the veryt ip of the beveled end of the needle touching the car t i lage .

The ffi1G act iv i ty is observed on a monitor oscilloscope when the subjectis asked to attempt quick jaw opening or re t ract ion of the tongue. Again,functional dif ferent ia t ion of the strap muscles is not possible on the basisof present knowledge, so that we must rely on anatomical expectation.Velopharyngeal Muscles

The peroral approach i s always attempted with the subject in a s i t t ingposi t ion for inser tion into the velopharyngeal muscles. The electrode-bearingneedle (usually with an angulated shaft) i s held by a pair of al l iga tor forceps.Levator palat in i (LEV). Insert ion i s made into the levator "dimple" onthe soft palate with the subject attempting sustained open vowel phonation.The t ip of the needle i s directed latero-cranio-poster ior ly approximately 10 mm

from the surface of the mucosa.Verification is made by asking the subject to repeat the production

of [s] . Marked act iv i ty can be observed for th is strong oral gesture i fthe electrodes are placed properly.

Palatoglossus (PG). The PG is the muscular component of the anteriorfaucal pi l l a r . This muscle is reached by insert ing the angulated needle intothe anterior pi l la r either cranio-caudally or in the opposite direct ion.Since the inser tion i s made under direct inspection, ver i f ica t ion is sa t i sf iedi f marked act iv i ty i s shown when the subject swallows.

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Palatopharyngeus (PP). In our EMG study, the PP is regarded as themuscular component of the poster ior faucal pi l l a r , although there has beensome controversy in the past l i t e ra tu re on i t s anatomical descr ipt ion (Bosmaand Fletcher, 1962; Fr i t ze l l , 1969).

The insert ion i s made into the posterior faucal pi l la r under directinspection. Verificat ion of correct placement i s , therefore, sat isf ied i fill1G act ivi ty is monitored during swallowing.

Superior const r ic tor (SC). The t ip of an angulated needle is directedcranial ly to reach the posterior pharyngeal wall la te ra l to the midline a tthe estimated leve l of velopharyngeal closure. The inser t ion i s made underinspection and, therefore, placement i s verif ied i f B1G act ivi ty is observedfor swallowing.Middle const r ic tor (MC). Inser t ion i s made using an angulated needledirected caudally into the poste r ior pharyngeal wall near the level of thet ip of the epiglot t i s . The tongue of the subject i s protruded and held forbet ter v isual izat ion of the s i te of inser t ion.Practically, precise discrimination of the upper portion of the middleconstr ic tor from the lower f ibers of the superior constr ictor i s d i f f icul t ,since the const r ic tor muscles of the pharynx are interlayered at the level

of t rans i t ion from on e to the other (Hollinshead, 1966). Therefore, i tshould be mentioned that what we attempt to examine as the middle constr ic tori s rather a topographical representation of the pharyngeal constr ic tor a tth is part icular level. Verif icat ion of electrode placement i s made inessent ia l ly the same way as for the SC.Suprahyoid and Tongue Muscles

These muscles are reached percutaneously with the subject in a s i t t ingor semi-Fowler posi t ion.Anterior bel ly of digastr ic (AD). The contour of the AD is palpable

i f the subject attempts to open his jaw by res is t ing the experimenter 'shand holding i t or i f he strongly pushes the t ip of his tongue on to theupper alveolar r idge with his mouth sl ight ly open. Inser t ion is made, withthe subject attempting ei ther one of the maneuvers mentioned above, a t apoint near the anterior attachment of the muscle to the mandibular ridge.The needle i s directed obliquely to the surface of the skin aiming at themuscle bel ly. Verificat ion is made by having the subject open h is jaw,a movement which should be accompanied by marked ill1G act ivi ty. There isl i t t l e possibi l i ty of contamination with other muscles.

Mylohyoid muscle ( M ~ ) . Inser t ion into the MH i s made near the ridgeof the mandible, l a t e ra l to the l a t e ra l margin of the AD and anterior tothe hyoid bone. The experimenter puts his f inger onto the f loor of themouth to palpate the t ip of the needle peroral ly. This technique is similarto that reported by Smith and Hirano (1968). (See Figure 6.) Verif icat ionis made if the EMG act iv i ty is monitored when the subject ret racts thetongue backwards or produces (k] repeatedly.

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CX>~

A Frontal Section of the Infer ior Portion of th eFace I l lust rat ing th e Direction of a NeedleInserted into th e Mylohyoid (A) and intothe Anterior Belly of Digastr ic (B)

gen iog Iossus

anterior

A Sagit tal View of th e Infer ior Portion of th eFace I l lust rat ing th e Direction of NeedleInserted into th e Genioglossus (C) andinto the Geniohyoid (D)

genioglossus

geniohyoid

A. belly of digastric c.B.Fig. 6

Note: A f ingert ip of th e experimenter is placedon the f loor of the mouth, close to thealveolar r idge , to palpate the t ip of theneedle. (This figure is a modification ofSmith and Hirano, Fig. 1, 1968.)

Fig. 7Note: A finger i s palpating to evaluate correctneedle placement in th e genioglossus.(This f igure i s a modification of Smith

and Hirano, Fig. 2, 1968.)


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This muscle i s so th in that electrode placement is not always satisfactoryin spi te of the fact that there is l i t t l e possibi l i ty of contamination withother muscles.Genioglossus (GG). A percutaneous approach is always taken, althoughthe peroral approach is possible as reported by previous authors (Sauerland

and Mitchell , 1970). The needle is inserted perpendicularly to the surfaceof the skin a t the midpoint between the hyoid bone and the mandibular ridgein the paramedian l ine . The needle i s then directed deep enough to be palpatedby the experimenter 's f inger inserted onto the floor of the mouth of thesubject . The technique employed in ou r experiment is the anterior GG placementdescribed by Smith and Hirano (1968). (See Figure 7.)

Exact placement is ver i f ied by having the subject protrude his tongue orswallow; vigorous act iv i ty should be monitored for these maneuvers. Lit t lepossibi l i ty of contamination with other muscles is expected i f the needle isdirected and palpated as described above.

Geniohyoid (GH). The needle is inserted in the paramedian l ine morecaudally than the inser t ion point for the GG, approximately 10 mm above thelevel of the hyoid bone. At th is level , the MH is almost a tendinous structurecovering the infer ior surface of the GH. The needle should not be inserted to odeeply but should be stopped af ter the penetration of that tendinous t issuewhich can usually be f e l t by the t ip of the needle. The estimated depth ofinser t ion i s approximately 2-2.5 em (Figure 7).

Veri f icat ion of the placement by observing the EMG s ignal does notseem to be straightforward since there is a conflict of opinions onthe function of th is muscle (Cunningham and Basmaj ian, 196.9). Accordingto our observation, however, there is some difference in the pattern of theEMG act ivi ty of th is muscle for swallowing and tongue protrusion of thatof the GG, with which the GH i s most l ike ly to be confused. Namely, asCunningham and Basmajian (1969) reported, GH act iv i ty follows with somedelay in time that of GG act iv i ty for the in i t i a t ion of swallowing, andfor simple tongue protrusion, the GH appears to be less active than the GG.Further investigation wil l be necessary for satisfactory EMG assessment ofth is particular muscle.

REFERENCESBasmajian, J .L. and G. Stecko. (1962) A new bipolar electrode for electro

myography. J . Appl. Physiol. 17 , 849.Bosma, J.F. and S.G. Fletcher . (1962) The upper pharynx: A review. Part I I ,Physiology. Ann. Otol. Rhinol. Laryng. 71, 134-157.Cunningham, D.P. and J.V. Basmajian. (1969) ~ l e c t r o m y o g r a p h y of genioglossusan d geniohyoid muscles during degluti t ion. Anat. Rec. 165, 401-409.

Fri tzel l , B. (1969) The velopharyngeal muscles in speech. An electromyographic and cineradiographic study. Acta Otolaryng., ~ 250, 1-81.Gaskil, J.R. and D.D. Gil l ies . (1966). Local anesthesia for peroral endoscopy. Arch. Otolaryng. 84 , 654-657.Harris, K. (1970) Physiological measures of speech movements: EMG andf iberoptic studies. Proceedings of the Workshop on Speech and theDentofacial Complex. ASHA Reports No. 5, 271-282.Hirano, M., Y. Koike an d H. van Leden. (1967) The sternohyoid muscle duringphonation: Electromyographic studies. Acta Otlaryng. 64, 500-507.

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Hirano, M. and J. Ohala. (1969) Use of hooked-wire electrodes for elect romyography of the intr ins ic laryngeal muscles. JSHR 12, 362-373.Hollinshead, V.H. (1966) Anatomy for Surgeons. (Vol. I : - Head and Neck.)New York: Harper and Row.Sauerland, E.K., and S.P. Mitchell . (1970) Electromyographic act ivi ty ofthe human genioglossus muscles in response to respirat ion and toposi t ional changes of the head. Bullet in of the Los Angeles Neurol.Soc. 35, 69-73.Shipp, T. -zl968) A technique for examination of laryngeal muscles duringphonation. Proc. 1st Int. Cong. of Electromyographic Kinesiology,Montreal, Canada, August 1968. 21-26.Shipp, T., W.W. Deatsch and K. Robertson. (1968) A technique for electromyographic assessment of deep neck muscle act ivi ty . L a r y n g o s c o p e ~ , 418-432

Simada, Z., Hirose, H., M. Sawashima and 0. Fujimura. (In press) An EMGstudy of Japanese accent patterns. Proc. for 7th International Congresson Acoustics, Budapest, 1971.Smith, T. and M. Hirano. (1968) Experimental investigation of the muscularcontrol of the tongue in speech. Working Papers in Phonetics UCLA.

10 , 145-155.Zemlin, W.R. (1969) The effect of topical anesthesia on internal laryngealbehavior. Acta Otolaryng. 68, 196-176.

EMGofArticulatoryMuscles Technique

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