Dept. for Speech, Music and Hearing

Quarterly Progress andStatus Report

Stuttering explained as aphysiological tremor

Fibiger, S.

journal: STL-QPSRvolume: 12number: 2-3year: 1971pages: 001-023

http://www.speech.kth.se/qpsr

STL-QPSR 2-3/197 1 1.

I. COMMUNICATION DISORDERS

A. STUTTERING EXPLAINED AS A PHYSIOLOGICAL TREMOR*

S. Fibiger

Definition

Stuttering is a communication disorder character ized by excessive in-

voluntary disruptions o r blockings in the flow of speech, par t icular ly when

such disruptions consist of repetitions o r prolongations of a sound o r a

syllable, and when they a r e accompanied by avoidance struggle behavior I

( f rom the Speech Foundation of America, 1970).

E tyrnology

The t e r m stuttering is a n onomatopoeia; so a l so the corresponding terms

in mos t of the other languages. One of the mos t onomatopoetic word for

stuttering i s "kohindahindal' which occurs in the Bantu language.

The Greek t e r m flbattarismos" i s , according to Hunt (1861), derived , f rom Battos. Herodotus (484 B. C. ) says that the Therean Battos, who had

been a s tut terer f rom his youth, consulted the orac le a t Delphi. The orac le

said: "Battos, thou come s t on account of thy speech, but King Phcebus

Appollo sends thee to Libya, in the land of sheep to dwell". After having

founded the colony Cyrene, he was, according to Pausanias (born 175 A. C. ),

cured of stuttering by the unexpected sight of a lion.

Introduction 1 Since the days of Moses** (The Holy Bible, Exodus, Chapter IV, verse

10) man has been writing about the speech disorder called "stutteringf1,

which is the mos t complicated and integrated speech disorder we know. I t

has been the subject of much wonder and r e sea rch since the t ime of Hippo-

k ra t e s (dead 377 B.C.) , but we still know very little about the nature of this

phenomenon.

* This work i s supported by grants f rom the Nordic Cooperation Council for Medical Resea rch (Nordiska Samarbetsnamnden fijr Medicinsk Forsk - ning) and by the Swedish Institute, and aided in p a r t by the Information Center for Hearing, Speech, and Disorders of Human Communication, The Johns Hopkins Medical Institutions, Baltimore, Maryland. The In- formation Center is a p a r t of the Neurological Information Network of the National Institute .of Neurological Diseases and Stroke and is sup- ported by contract No. PH 43-65-23.

"$6 Moses was a s tut terer himself.

STL-QPSR 2-3/1971 2.

In non-disordered communication, i. e . normal speech, there i s the

potential fo r the individual to be relatively f ree and consciously aware of

his feelings and thoughts a s they relate to his environment. This fluent

freedom of expression gives r i s e to the feeling of the unity and autonomy

of the self, thus facilitating the ability to communicate freely with others.

The s tut terer lacks this feeling of freeaom in the speech situation prec ise-

l y because stuttering i s a functional disorder in the communication situa-

tion. Therefore, stuttering provides one cf the mos t socially disabling

afflictions to which a human being can be subject. I

There a r e qui te a number of theories about the nature and origin of

stuttering, explaining this defect f r o m different points of view, but the au-

thor of this study i s anxious to point out that stuttering i s not only a medic-

a l problem, not only a phonetic problem, and not only a psychological

problem, but a problem which involves a l l branche s of knowledge with r e l a -

tion to the human being. Many different theories about the physiology and

psychology of stuttering have been elaborated. Without derogating these 1 dedicated and quite bril l iant stuttering r e sea rch workers , the author of this

study does not believe that they have a s yet come up with the answer of the

problems of stuttering and most of them have not taken into account that

stuttering is an integrative whole and cannot be studied in pa r t s a s the

blind men in the s tory studied the elephant.

Examinations about s tu t te rers ' muscle coordination, laterali ty, and

cerebra l dominance have 'been done throughout this century, but according

to my impression the conclusion i s that s tu t te rers do not significantly

differ f rom the normal population organically, although some interesting

observations have been made on that one percent of the human population

who a r e s tut terers . However, no one will deny that the speech performance

i s acoustically different in s tu t te rers versus normal spezkers. Because a l l I speech generated by man i s a resu l t of muscle activity coordinated in time

and space, the muscle activity must a l so be different in s tu t te rers and in

narxnal speakers. But when the stutterer does not stutter.'?, the speech pe r - formance i s very like - if not identical to - the speech performance of a

normal speaker.

+c Most s tu t te rers do not stutter when they a r e talking to themselves, speaking in chorus, o r singing (von Wiechrnann and Richter (1966) and ~ o r j v e l c and ~angovzt ( 1967)).

STL-QPSR 2-3/197 1 3.

How can we progress in s h t t e r i n g r e s e a r c h ? We can, for example, t r y

to c r o s s traditional vocational boundaries and knowing that the overt symp-

tom of stuttering often changes, when the social environment o r the psycho-

logical factors a r e changed, any hypothesized mechanism of stuttering mus t

be shown to vary with emotional states. Hence we can a s k ourselves:

"Which physiological phenomena can undergo changes when the psychological

factors a r e changed ?"

Physiological t remor ------------

One physiological phenomenon which undergoes change under s t r e ss i s

the physiological tremor++ (Lippold, Redfearn, and V U ~ O (1959); Graham

(1945); Clare and Bishop ( 1949); Sugano and Inanaga (1960); Dossytchev, I

Vojava, and Nemtchine (1967)).

Under a variety of circumstances, normal o r pathological, motor activity

may take the form of periodic pulses of contraction instead of the normal

smooth tetanus. In normal persons i t is often seen in connection with fatigue

o r excitement (Bishop, Clare , and P r i c e (1948)). They have a lso noted that

under the influence of adrenalire o r fatigue, t remor may be mere ly eas i e r to

elict , o r involuntarily present and even difficult to suppress. T remors

mos t commonly found can be divided into two groups: those in which opposing

muscles contract in alternate bursts , of which Parkinsonian t remor i s the

classical example, and those in which the burs t s a r e synchronous in opposing

muscles . The la t ter type shows increasing amplitude under condition of ne r - vous tension. These two types of t r emors appear overtly a s "coarse" and

"fine", respectively, although various complications of pattern, frequency,

and intensity confuse this correlation. All normal subjects can induce an

alterning, o r clonic, t remor of the a r in by clenching a r m and shoulder

muscles and voluntarily initiating a reciprocating movement. Many normal

subjects can induce a synchronous t r emor , par t icular ly in fo rea rm muscles ,

by simple clenching without voluntary movement, and under certain situations

they may show involuntary t remor.

It i s a common experience that fatigue, prolonged s t r e s s , either physical

o r emotional, and cer tain drugs induce o r accentuate t remor . F o r instance, Clare and Bishop (1949), note that an involuntary t remor appeared a t i r r e g -

u lar intervals, during r e s t or with minimal contraction of muscles in a

9 Also called: normal t remor , minor t r emor , micro- t remor , micro-movement, mic ro -vibration, o r body-vibration.

STL-QPSR 2-3/197 1 4.

normal subject, a student, who served a s a t e s t subject, shortly af ter a

final examination, In another subject, examined 24 hours af ter a tennis

game, when the a r m felt fatigued and uncomfortable, such a t remor appeared.

Physiological t r emor of voluntary contraction l imi ts our' f inesse of motor

control a s , for instance, i s apparent when we attempt to thread a needle o r

wield a soldering i ron, and it has been recognized and recorded since 1886

(Schafer, Canney, and Tuns ta l l (188 6 ) ) , Despite many investigations, how-

eve r , the mechanisms producing this t remor a r e sti l l uncertain, but we know

a t a l l events that they a r e involuntary movements resulting f rom the synchro-

nous contraction of muscle groups (Awazu (1965)) which produce rhythmic o r

alternating movements with a m-ain frequency a t 8 - 12 Hz. T remor var ies

considerably in different subjects and in the same subject a t different times.

Experimental studies on t remor mus t take into account such normal variations.

The phenomenon of physiological t r emor can be broken down into a num-

ber of physiological fac tors , o r components, of which the principal ones a r e

the periodic action and inaction in a given muscle involving mutual facilitation

of motor units; synchronous innervation of the adjacent and opposing muscles.

These factors can be detected in the activity pat tern of many normal subjects

who show varying degrees of tendency toward t r emor , especially under ne r -

vous t e ~ s i o n , s t r e s s , excitement, o r fatigue, o r during considerable effort.

T remors tend to manifest themselves a t the s t a r t and particularly during the

relaxation of effort, especially if relaxation i s ca r r i ed out gradually (Clare

and Bishop (1949)). T remor of the skeletal muscles i s only one of the rhyth-

mic, cyclic phenomena which occur in the human organism. Biologic osci l -

lation may be mechanical, a s in the case of the cardiac ilnpulse, o r bio-

e lectr ic , a s the m-rhythm of the cerebra l cortex. It may be extremely rapid,

a s in the electroinyograrn, o r quite slow, a s in the menstrual cycle of the

human feinal e.

Physiological t r emor a t r e s t i s invisiblc to the nalced eye, l i e s entirely

in the micron range, and mus t be detected and alrlplified electronicaily for

study. Physiological trenlor on intcntioli+t i s likewise difficult to see but i s

grossly apparent ill such s tates a s anxiety and llypertllyroidism. Brumlik 1 (1962) defines the physiological t r emor a t r e s t in the 3 to 80 IJ, range and

physiological t remor on intention a s ranging f rom 100 to 1000 y. There i s

it Intention: The ac t o r an instance of determining mentally upon some action o r result .

STL-QPSR 2-3/197 1 5 .

considerable evidence that the increased tension of the skeletal muscles con-

stitutes one of the important physiological manifestations of emotion, and the

association of t r emor and emotion has long been recognized. P h r a s e s such

a s "shaking with fear f : and "trembling with emotion" a r e familiar in every-

day life. The occurrence of t r emor a s a resu l t of exertion o r physiological

fatigue i s also frequently observed clinically. Graham (1945), Clare and

Bishop (1949), Friedlander (1956), Lippold, Redfearn, and ~ u ' c o (1959), and

Dossytchev, Vojava, and Nemtchine ( 1967) have s t r e s sed that the amplitude

of the physiological t remor - which, a s previously noted, seldom i s visible

with the naked eye under optimal psychological conditions - increases in con-

nection with the following factors: s t r e s s , clnxic t y , nervousness, mental ef-

fort , physi cal exertion, pain, and respiration. According to Eagles , Halliday,

and Redfearn (1953) the medium frequency band of the t remor (6-12 HZ) is the

band which i s chiefly influenced by emotion and fluctuating "nervous tensiont'.

Lippold, Redfearn, and ~ u c ' o (1959) have shown that the t r emor in s t r e s s situa-

tions - in casu: when normal subjects were anticipating the entrance inter - view to Medical School - i s very alike the t r emor in anxiety patients, which

means that the t r emor frequency i s the same a s in normal subjects but that

the amplitude of the t r emor is greatly increased.

Many investigators have drawn the conclusion that s tu t te rers have a high

degree of anxiety, shyness, and insecurity (~an tos t e fano (1960) loc. cit. ), and

Santostefano (1960) say that stuttering and being a s tut terer places an individ-

ual ir, a fa ir ly constant state of s t r e s s because of actual and continually im-

minent negative reactions by the environment and because of the s tu t t e re r ' s

own evaluation and interpretation of the handicap in t e r m s of his self-esteem,

security, and identity. Also van Riper (1963) wri tes about s t r e s s and stut-

tering and Edgren, Lennderson, and Levi (1969 and 1970), and Edgren (1969)

point out that stuttering i s precisely a fo rm of "speech stress". Wilson Jr. I and Icunkle (1953), Wright, Keele, Neil, and Jepson ( 1965), Foley, Marsden,

and Owen (1967), Mar sden, Foley, Owen, and Mcf'illis te r ( 1967), Mar sden

and Owen (1967). and Marsden and Meadows (1968) have shown that the ampli-

tude of the physiological t r emor increases to a concentration of 1-10 pg/l

after ad rena l i~e has been injected into the blood, and i t has been calculated

right, Keele, Neil, and Jepson (1965)) that under s t r e s s the adrenal medulla

pezrctes adrenaline a t a ra te of about 10 pg pe r minute, which according to

STL-QPSR 2-3/197 1 6 .

Foley, Marsden, and Owen (1967) i s the optimal quantity for raising the

amplitude of the physiological t remor. Fur thermore , Leander son and Levi

(1967) and Edgren, Leanderson, and Levi (1969) have found that the speech

situation for s tu t te rers i s accompanied by a r i s e in the excreation of adrena-

line by almost 300 70. Confronted with a l l these facts about stuttering, s t r e s s ,

adrenaline, and physiological tremofi, an examination of the motor speech

apparatus of s tu t te rers in a speech situation with respect to physiological

t e rmor would be motivated.

Methods and Materials

The physiological t remor can be recorded in different ways. The method

applied in this study i s the electromyography (EMG). In this technique the

action potentials of nluscle f ibers - which originate a t the motor end-plates

and a r e triggered by incoming nerve impulses a t the myoneural junction - a r e amplified and can be registrated on cathode - ray oscilloscope, film, tape,

and/or paper.

EMG-studies of the activity in the motor speech apparatus a r e of grea t in-

t e r e s t to persons who stutter, inasmuch a s ora l speech consists of sequences

of muscle contractions which a r e highly integrated in tirne and space, and

which likely a r e effectuated by means of a coordination between phone tic ru les

and usual neurophysiological activities. The sequence s of activity in the

speech apparatus must be much m o r e exact than any other voluntary action,

and for this reason i t i s very easy to disrupt this sequence. This circum-

stance gives the speech scientist the possibility of making reproducible r e - cordings of very complex sequences of human voluntary act ivi t ies , a s well

a s the possibility of recording and analyzing the muscular dyscoordination

when a person is stuttering.

The EMG-technique used in this study i s close to the method described by

ohman, Leanderson, and Pe r s son (1965 and 1966), ohman (1967), Leanderson,

ohman, and Per s son (1967)~ Per s son , ahman, and Leanderson (1965 and 1968),

Pe r s son , Leanderson, and Ohman (1969), Leanderson, Pe r s son , and Ohman

(1930), and Fibiger (197 lb). The EMG-amplifiers a r e constructed by J. Li l-

jencrants a t this laboratory. In most cases a 60 dB EMG-preamplifier was

used in combination with a Grass Polygraph D. C. Driver Amplifier, model

Van Riper ( 1963) wri tes a b m t something he calls the "Stuttering Tremor t t when he describes the "Third Stage of the Development of StutteringfJ.

I Fig. I-A- 1. Muscles of facial expression.

Fig. I-A-2. Electrode positions.

STL-QPSR 2-3/1971 8.

examinations of the ar t iculatory facial muscles a r e appropriate. But these

muscles a r e by no means the l eas t interesting ones; they t ransmi t a g rea t

deal of phonetic and linguistic information, which i s of especially grea t value

for deaf persons with some degree of hearing loss .

The co r rec t placement of the needle electrode in the muscle i s controlled

by a cathode - r ay oscilloscope o r a Mingograph. In this connection i t i s worth-

while to emphasize that the needle electrode does not cause pain af ter the skin

i s penetrated, and the cannula can be moved in and out of the muscle with no

reaction a t all. If necessary, the skin surface i s anaesthetized with lidocain-

aerosol. The speech signals a r e recorded using a Sennheiser microphone,

model MD 421, a t a distance f rom the subject of ca.25 cm, and the FM-tape

recorder . In one subject the speech signals were also recorded with a con-

tact microphone, developed a t the Department of Speech Communication f rom

the sub-minor earphone SM-HA, made by Danavox Internationa1,Denmark.

This microphone was attached on the outside of larynx with an adhesive disc ,

S o r m a s c a l 1500, made by 3M Company, Minnesota, U. S. A.

During the experiment the subject \-/as sitting a s comfortable a s possible.

The subject read words f rom the dictionary of the Swedish Acade,my ( ~ v e n s k a

~l l rademiens Ordbok), connected text, o r he spoke spontnneously. It was con-

sidered important, to employ meaningful words instead of nonsense-words to

s e c u r e a m o r e n a t u r a l s p e e c h s i t u a t i o n . Each tes t sess ion las tedaboutone ,

hour. Recordings fronz four s tu t te rers were studied in detail. All of them

were adult ma les between the ages of twenty and thirty; the youngest one, a

s tu t te rer , was 23 yea r s old. All the subjects had suffered f rom stuttering

since childhood and had received logopcdic therapy - with poor therapeut ic

resu l t s - during long periods. 1\11 of the subjects belong to the P-Club, a

lay association of chronic s tut terers .

Resul ts I The electrornyograms (EMG) hzve been studied in every detail and no

neuro-pathological deviations have been observed. But i t i s obvious from the

EMG-recordings that the ~ l lusc lc activity in the facial muscles during stut-

tering i s an activity which a r i s e s f rom a physiological t r emor with exagger - ated n~nplitude (Fig. I-A-3); thus the EMG-activity i s of the same intensity

during physiological t remor a s i t is when producing ar t iculatory movements.

Rut i t i s a l s o obvious that no t r emor i s seen in s tu t te rersdur ing fluent speech

STL-QPSR 2-3/197 1 9.

nor in normal speakers ( ~ i g s . I-A-4 and I-A-5). The main frequency band

in the subjects studied he re was 7-10 Hz, with the main frequency 8 Hz, and

the synchronous activity in the antagonists was very well established. How-

ever , the t r emor activity often s t a r t s in only one o r some of the muscles

and then af ter some activity-bur s t s in these muscles a l l of the muscles in

consideration - in casu four muscles - a r e involved in the t r emor activity

(Fig. I-ii-6). In the subjects examined he re , the t r emor activity in the

symmetr ical pa i r s of muscles i s synchronous (Fig. I-A-7). It i s , however,

often the case that the muscle on one side s t s r t s one burst ea r l i e r than in

the symmetr ical one ( r ig . I -LL8) , but no general statement about the p r e -

dominating side can be made.

Inspection of the electromyograms can sometimes reveal that only every

second of the synchronous t remor bursts i s seen o r that every second burs t

has a lower intensity. This phenomenon i s especially prevalent during

phonation, and because of this, a careful investigation of the interaction

between t r emor activity and phonation was made. Inspections of the electro-

myograms give r i s e to the a s sumption that the t r emor often l i e s latent but

i s suppressed o r interacted upon by phonation. The interaction between

t remor and phonation i s sometimes manifested in that the phonation only

suppresses the t r emor in some of the muscles , while the t r emor i s s t i l l

recognized in the other muscles (Fig. I-A-9).

As stated by ~ a n g o v j (1967), ~ o r j v e k and ~ a n g o v h (1967), and Wingate

(1967) the main problem of stuttering i s the initial tonus o r the prephonation,

This i s a lso seen in this study; the t r emor activity i s much more marked

and frequent under prcphonation (Fig. 1-11-6 and I-A-10).

But how does the t r emor decrease and cease, and how does normal a r -

ticulation s t a r t ? Analysis of the e l e c t r i i ~ l y o g r a ~ x ~ s shows that here the

phonatory attenzpts a r e very in~pos tant , because the acoustic output (anscc-

cessfully articlllated spec,ch elenlents) suppresses the tren?or activity in

the ~ x u s c l e s . The recordings show that about 100 m s e c without trelnor ac -

tivity nus t precede before normal articl~lati,:n can talie place (Figs. I-lAi-8

a d 1 - 0 ) It thus seems that the condition fo r norr~la l art iculated speech

i s that there i s no t r emor activity during the time before the acoustic onset

of a phoneme, where muscle act ivi ty in the articulatory apparatus i s ne-

ces sa ry for nornlxl fluent speech. A f : l iov~ing cource of events i s seen in

the EMG: The t r emor activity stops and the normal muscle activity for the

STL-QPSR 2 -3/197 1 10.

articulation s t a r t s , but before the acoustic onset, a new t r emor in the facial

art iculatory muscles has s tar ted, the articulatory muscle activity ceases ,

and the stuttering continues (Fig. I-A- 11).

An activity of t r emor burs t s starting under normal articulated phonation

influences the intensity of the phonation which is decreased o r ceased depend-

ing on the intensity of the t remor and the intensity of the phonation. This ef-

fect on the speech i s effectuated with a delay of about 50-100 m s e c af ter the

f i r s t t r emor burst , depending on the amplitude of the t r e m o r ( ~ i g . I-A- 12).

Generally, phonation of low intensity i s eas i e r to interrupt than one of

grea ter intensity. It can be noted that if an articulated phonatory attempt

coincides with a t remor burst , the phonation will decrease in intensity o r

cease 50- 100 m s e c af ter the t r emor burst has s tar ted, depending on the

amplitude of the t r emor ( ~ i g . I-A- 13).

One of the subjects (LSA) t r ied to modify his stuttering symptom in a

way described by Sheehan (1970). This modification of the stuttering syrnp-

tom involves inter alia a smooth syllable prolongation and i s called a "slide".

On the electromyograms recorded f rom LSA i t was seen that the amplitude

of the t r emor activity was suppressed under continuous phonation (Fig.

I-A-14). In the recordings of the other subjects i t was a l so seen that the

phonation or the phonatory attempts suppress the activity of the t remor ; in

other words, if the s tu t te rer can maintain an acoustic output the t r e m o r a c -

tivity wi l l very soon cease.

It i s difficult to observe the correlation between the suppression of the

t r emor amplitude and the sound frequency of the acoustic output of the

stutterers, because the intensity of high-frequency consonants of the unsuc-

cessfully articulated speech elements i s very low, but i t i s obvious that there

exis ts some kind of proportionality between the suppression of the t r emor

and the intensity of the acoustic output f rom the subjects.

General discussion

Redfearn (1957) found that the t remor amplitude i s greatly increased

- especially in the 8-10 Hz band - in morbidly anxious persons, and Lippold,

Redfearn, and VUZO (1959) stated that this was a l so the case in normal sub-

jects under s t ress .++ Car r i e (1967b) found that the t r emor of anxious subjects

.u A s noted under t'Physiological t remor" also hyperthyrodism elevate s the t remor amplitude (Brumlik (1962)). This fact i s of special interest because Gordon (1928) has shown that stuttering m a y be produced by I

thyroid medication. I

STL-QPSR 2-3/19? 1

Text to figures I-A-3 to I-A-I4

Fig. I-A-3. Mingogram. Stuttering on C f 1 in the Swedish word

lrsj l lsfr id" - LX9r :ls, fri:dl * (peace of mind) under the

fir st reading trial. The tremor frequency is ' about 8 Hz.

Fig. I-A-4. Mingogram. Normal fluency on [f f in the Swedish word

rlsj$ilsfridlf - [X$ ~: l s , f r i : d l (peace of mind) under the 60th

reading trial. This mingogram is taken from the same

recording a s in F ig . I-A-3 and the subject and the elec-

trode placement are unchanged. The adaptatiolrmc is

well established.

Fig. I-A-5. E ~ ~ / s ~ e e c h oscillogram - polygram from a normal

subject. No tremor activity i s seen. With the kind and

most generous permission from Ohman (1967).

Fig. I-A-6. Mingogram. Stuttering on the initial consonant [ 5 1 in

the Swedish word lr&llsfridfr [ 6 E :ls, fri:dl (peace of J

mind) under the f i rs t reading trial. Note that the tremor

activity s tar ts successively in M. depressor labii in-

ferioris, M. orbicularis or is inferior, M. orbicularis

or is superior, and M, levator labii superioris.

Fig. I-A-7. Mingogram. Stuttering on [ 4 1 in the Swedish word Y

Irfrack&6rtlt cXfrak, 5ce t ](tail of the tails). Note

that the tremor activity in symmetrical pairs of

muscles is synchronous.

4C This subject i s from Gothenburg, where the C i s more 5 frequency than [ r 1. In Stockholm [ f I i s more frequent

J than [ 5 1.

** Adaptation: The reduction in frequency or severity of stuttering

a s a function of repeated utterances in a relatively constant speak-

ing situation; the stutterer ' s measured reaction to a constant

situation. Adaptation is often measured in terms of the observed

frequency of stuttering during successive readings of the same

passage (from the Speech Foundation of America, 1370).

STL-QPSR 2-3/19? 1 12.

Fig. I-A-8. Mingogram of spontaneous speech. Note e specially that

the t remor activity s t a r t s in M. depressor labii infer ior is d.

In the next period the activity is a l so seen in the two syrn-

met r ica l muscles , M. orbicular is o r i s inferior d. & 1.. In

the third period the t r emor activity is seen in a l l four mus -

cles. Note also that about 100 m s e c without t remor activity

must precede the vowel which opens a passage with fluent

speech, i

Fig. I-A-9. ~ i n ~ o g r a m . Stuttering on E: 3 in the Swedish

word "*lsfridtt [Xfi E :1s, of mind). Note J

that the intensity wax and wane in relation to the acoustic

output f rom the subject in such a way that only every second

t remor bur s t - especially in M. levator labii superior is d.

and M, orbicular is o r i s superior d. - i s seen.

Fig. I-A- 10. Mingogram of spontaneous speech. Note especially the ~ t remor activity under prephonation. Note a l so that about

100 m s e c without t remor activity must precede the vowel

which opens a passage with fluent speech.

Fig. I-A-11. Mingogram. Stuttering on [ f ]in the Swedish word

"sjalsfridl ' - r5 E :ls, fri:d ] (peace of mind). Note that I

the articulatory muscle activity in M. depressor labii in-

fe r ior i s d. twice is interrupted by t remor activity before

the acoustic onset of [ ri:d 1 . Fig. I-A- 12. Mingogram of spontaneous speech. Note that the phonation

is inhibited by the t remor activity.

Fig. I-A-13. Mingograrn. Stut ter ingon [ $ I and [ t r 1 in the non-fluent

Swedish word ttsjllvskird"* - rX5 ~ l ~ , 5 i:d I . Note that the

t remor which s t a r t s simultaneously with a phonatory attempt

of C E I inhibits the phonation totally about 100 m s e c af ter

the s t a r t of the t remor burst.

Fig. I-A-14. Mingogram of "slidingt' spontaneous speech. Note the in-

hibition of exagerated t r emor activity in connection with the

smooth syllable prolongation.

Y " sjalvskird (or sjaivskirad) honung": an old Swedish t e rm fo r "selfdrained honeytt.

SPEECH OSCILLOGRAM f f f

Me DEPRESSOR LAB11 INF. D*

i . -- - M. ORBICULARIS ORIS INFO D.

f 1 S E C

4 Fig. I-A-3.

SPEECH OSCILLOGRAM . . . . . .

M, LEVATOR LABII SUP. D.

M. DEPRESSOR LABII INF. D. . Q

M. ORBICU LARIS ORIS SUP. D.

M. ORBICULARIS ORFMF. D.

t 1 S E C 1 Fig. I-A-4.

M. DEPRESSOR LAB11 INF. D.

. i ' 3 ' '

Me ORBICULARIS ORIS SUP. -D.

-- 1 S E C

Fig. I-A-6.

t

M. DEPRESSO~ LABII NF. D.

1. 100 MSEC

.. . .

Fig. I-A-7.

.. . --. . --

CONTACT MIC.

6 L

. M. ORBICULARISORIS INF. D.

M. DEPRESSOR LABII INF. D

k

)I--------------.J. ' 100 MSEC

Me LEVATOR LABII SUP. D. .. I

. . Fig. I-A-9.

- - .

100 MSEC Fig* I-A-10.

.-

CONTACT MIC. , . :.

I !

Me ORBICULARIS ORIS INF. D,

t

I

i . 8 ' M. ORBICULARIS ORIS INF. L,

I 5

1

1 .

- 100 MSEC

Fig. I-A-12, . .... .. .

?.

M, ORBICULARIS ORIS SUP. D.

- - - - ~ h ~ u ~ ~ ~ . L w * ~ ~ b w ~ r v r \ + M. ORBICU LARIS ORIS INF. D.

Fig. I-A-13.

. - . .. . - . .

M. DEPRESSOR LAB11 MF; D, ., , .. 100 MSEC

M. ORBICU LARIS O R E INF, D.

M, DEPRESSOR LABII INF. D.

'v'+wi-A*'+ 4+ru~.wryi. .i/';+; M, ORBICULARIS O R B INF, L.

--

)----------------i 100 MSEC Fig. I-A- 14. Thir figure continue e on next page. M, DEPRESSOR LAB11 INF. L,

3. .-. r 1 3'- -s.zi--z

. . .s-.--. --=x..7-::-.. -.=i--

-----.

3- .,. -- s.--- .SEE*. . - - SL --

-..---;, - . .- .--=.c-=_ ----. - . 2--

. . - 3 .. ....,--- . - -.. --. .- I----

%--. 2zz--. .- - , ---- 2c-.m- -.

___---- "-&- .- .a- -.-

-SF-- . ..-=: .= .--,- .-. -

3e-- ;=P - - - - -"- .&= -- .--*.--

.-% . .-a- -.. - *:--- --

%

37- -e:. -. .z.... s%=&. ->- . e.. ..:-:.

3- --- - e. . . . . . . - . >iE,- .

...... =$= - . .- . . - . . -- :.. . LL .

-2E- --.-A,-- /--... --

--.-. -- 2- >& --. ..

---- -.- . . . . .> . <-

. .--. -. cb.-- -

.- ---:-=-. -.

-- - ---.. - - --:-rC -. -- - --?- .-

uz4 -t-- u

-=='Y.--- -A=-. - --.- xi. - - -- - a,

=LA-

-.&-<-. -- -- 7.F.- - . - -.

-. ..- -' - .. d- -- &-: ry?>..' =..-

---z*-- -- - -. . -- - SL--. 2- ---I+ ,-.-.

-LC7=,. %

---.- .- -. -----_

STL-QPSR 2 -3/197 1 13.

differs from that of the controls in that I ) there was a greater average

amplitude, and 2) the 7-10 cps components were relatively more prominent

than other components in the 4- 12 cps range. The frequency found in those

studies coincides very well with the t r emor frequency which i s found in this

study, and the author therefore concludes that the overt symptom of stut-

tering i s precisely a physiological t remor in the motor speech apparatus

with an exaggerated amplitude, induced indirectly because the speech situa-

tion i s a s t r e s s situation f o r the s tut terer , and more directly by the in-

creased adrenaline excretion.

The number of subjects in this study i s too small to convincing prove

that the stuttering symptom manifests itself more readily a t the 8 Hz t remor

frequency than a t the 10 Hz frequency which is the mean frequency of physio-

logical t r emor in normal adult subjects. This hypothesis, however, i s of

considerable interest . F i r s t of a l l , i t i s important to point out that a t r emor

frequency of 8 Hz i s within the normal range of 8-12 Hz. Fur thermore , the

t r emor frequency in children - where stuttering generally i s more f r equene - i s according to Marshall (1959) 5-6 Hz and increases abruptly about the 10th

yea r , and Zdunkiewicz and Gorynski (1968) found that the physiological

t remor decreased a s age increased, particularly f rom the 15th year . The

fact that many children recover from the stuttering symptom may also be

seen in the general connection that children a r e apparently clumsy in p e r -

forming fine movements, which may be related to the more random nature

of their motor activity. It i s well known that normal fluent speech involves

a very fine motor coordination in time and space with a s many a s 10,000 to

15,000 neuromuscular events per minute (Lenneberg (1967))) which only

Homo sapiens can perform in spite of the fact that most mammalians have

lungs, larynx, tongue, l ips, and all other anatomical details which a r e nec-

e s s a r y for production of sounds. The nature of the neural pathways respon-

sible for adult motor finesse i s unknown.

Graham (1945)) Friedlander (1956)) and Marsden, Meadows, Lange, and

Watson (1969) point out that the shape of the physiological t remor spectrum

is very character is t ic and rather constant for an individual, but that i t var ies

in different subjects in the same way a s voice and the stuttering symptom do.

* There i s a great spontaneous recovery from stuttering - according to Sheehan and Martyn (1970): 80 Oib - mainly in the two periods of life, 11-14 yea r s and 18-22 years .

STL-QPSR 2 -3/197 1 14.

Only the amplitude var ies within grea t ranges, accentuated by s t r e s s , an-

xiety, fatigue, hunger, and senility. The predominating frequency found

he re (8 Hz) may also be seen in connection with the fact that there i s an

inverse relationship between frequency and amplitude. Graham (1945) and

Friedlander (1956), and Lippold, Redfearn, and V U ~ U ( 1959) note that the

most striking feature of physiological t remor i s the fact that i t has com-

ponents in a l l the frequencies a t leas t up to 30 Hz, and that under isometr ic

recordings the amplitude i s large in low frequencies, gradually diminishing

as the frequency increases .

Brumlik (1962) has remarked that the peak frequency of the t r emor is

elevated f rom 7-8 Hz to 7-10 Hz when the muscles a r e activated maximally,

which i s in accordance with a tendency noted in this study. According to

Clare and Bishop (1949) the physiological t r emor , typically synchronous in

antagonistic muscles does not build up in amplitude a s the contraction con-

tinue s , a s i s often observed in the Parkinsonian t r emor , in which g ross

movement is adequate to se t up reciprocal s t retch stimuli reinforcing the

initial periodicity. If antagonists a r e involved synchronously a t a higher

frequency than 10 Hz, no visible t r emor movement may result .

The observation made in this study, that the overt symptom of stuttering

i s established with a t r emor frequency of about 8 Hz, and not with the mean

frequency for physiological t r emor , 10 Hz, may a lso be viewed in light of

the fac t that stuttering often i s a repetition of syllables. But how can the

t remor frequency in the articulatory apparatus be effected by the repet i -

tion f syllables ? To answer this question we mus t keep in mind the ra te

of repetition of syllables o r the d iado~hokine t id ' s~eed , since the syllable

i s the ' 'true basic unit" in speech (Stetson (1951)) and because the physio-

logical correlate to the syllable is the breath pulse. Lenneberg (1967) and

Lehtonen (197 1) have stated that the diadochokine tic speed normally i s about

6 syllables pe r second and that i t can increase to about 8 syllables pe r

second, and occasionally even 9 syllables per second for the duration of a

few seconds. Also Hudgins and Stetson (1937) found that the relative speed

of articulatory movements l i e s in the interval 5.7 to 7.7 pe r second. Len-

neberg (1967) a l so stated that a temporal unit of 160 m s e c f 20 m s e c

(-J 1 7 .'1 Hz, 5.5 Hz [: ) appears to play a role in general psychological

.re Diadochocine sis is making of repe Wive alternating muscular move - ments , such a s tapping the foot, tapping the finger, ra is ing and lower- ing the brows, and opening and closing the jaw.

STL-QPSR 2-

and neurophysiological processes . This correlated to the previously men-

tioned fact that the phonatory attempts influence the t remor burs t s and may

lead to the assumption that the frequency of the t r emor i s established a t the

c-Aaxirr,urri ra te of repetition of syllablcs. The fact that this i s the maximum

ra te of repetition of syllables may have a connection with the well -known

fact that stuttering often appears in connection with cluttering, where the

ra te of repetition of syllables i s higher than with normal speech (von Seeman

and ~ o v h k (1 963)).

As noted previously sometimes the left muscle has the grea tes t amplitude

and sometimes i t i s the (symmetr ical) r ight muscle. It m a y be a consequence

of the placement of the electrode, but Brumlik (1962) notes that the ampli-

tude of the t remor of the lef t upper l imb was of grea ter magnitude than the

right one in some of the subjects he studicd, but in others , the t r emor of

both the upper l imps were of the same amplitude. Zdunkiewicz and ~ o r ~ A s k i

(1968) r epor t that in al l right-handed children examined, the left hand was

found to have grea ter t r emor than the right one, and the opposite was true in

left -handed children.

As noted under "Results"al1 the subjects exarnined in this study have s im-

i la r frequency on both s ides of the face, which m a y be seen in connection

with the findings of van Buskirk (1962) which indicates that when comparing

the two sides of the subjects, 34 OJo had frequencies differing f rom one side

to the other.

It has been postulated by many authors that the electroencephalogram

(EEG) of s tu t te rers is not fully normal in every aspect. F o r a review: see

Langov& and MorLvek (1966) and Beech and Franse l la (1968). The E E G

changes in s tu t te rers a r e mainly diffuse and unspecific. Some authors pos - tulate a slower a -rhythm (e. g. Fr i tze l l , pe ters&, and ~ e l l d h n (1965), and

~ a n ~ o v & and MorLvek (1966)), and luiorjvek and ~ ~ n g c v ~ (1962) say that

s tu t te rers have a grea ter amplitude of the CY -rhythm. These two attributes

of the CY -rhythm in s tu t te rers a r e the same attributes a s we find in the phy-

siological t r emor of s tu t te rers . Therefore the relations between physiolog-

ical t r emor and EEG a r e of considerable interest .

Ozaki, Sato, Awazu, Mimura, Honda, Teramota, and Kitajima ( 1962)

s t r e s s the correlation between the t r emor and EEG, and according to Lippold

(1970), and Lippold and Novotny (1970), the CY -rhythm in the EEG i s an a r t e -

fact, generated by the physiological t remor. Lippold and Novotny have a l so

STL-QPSR 2 -3/197 1 16.

stated that curves for t r emor frequency against age and a-frequency against

age coincide. They a lso mention that fatigue and a grea ter t r emor ampli-

tude of the extraocular muscles can be produced experimentally by asking

the subject to follow a moving object with his eyes; af ter some time the I

amount and amplitude of the a-rhythm increases . The control experiment I !

which involves a steady fixation of an obje ct while the background is moved

(in that way producing the same retinal stimulation) does not resu l t in an in-

c rease of a-rhythm. I

These fac ts a r e well in accordance with the above-mentioned changes of

EEG in s tu t te rers and also the assumption of Sheehan (1970) that the stutter-

ing symptom i s improved when the s tut terer has eye-contact with the inter-

locutor. I t i s normally very difficult for a stuttering person to have eye - contact with the communicated subject; normally the s tu t te rer ave r t s and

roves his eyes under speech communication situations. But if the s tu t te rer

concentrates on visually fixating on the inter locutor 's eyes, h i s eyes can

be a t r e s t , the t r emor amplitude decreases , and the stuttering symptom is

improved to some degree.

Exaggerated t r emor amplitude in the speech apparatus of a s tut terer in

a speech situation may be seen in conilection to the well-known fact that the

proportion of male s tu t te rers to female s tu t te rers is about 4 to 1. Car r i e

(1967a) has shown that the amplitude of the t r emor in anxious ma les is the

double of the tremor xinplitude in anxious feillales, and as previously noted,

Lippold, Redfearn, and VUEO (1959) have stated that the t r emor in s t r e s s

situations i s very alike the t r emor in anxiety patients.

As de scribed under f 'Results" phonation and phonatory atteinpts diminish

the t remor. It i s well-known f rom stuttering therapy that a change in the

acoustic stimulus a l t e r s the stuttering symptom, a s i s seen during a

o r in experiments with delayed auditory feedback (DAF), whik noise stimula-

tion o r when singing o r speaking in chorus. This fact only underlines the

well established phenolnenon that auditory feedback and other acoustic phe - nomena produce changes in the pe r fo r~nance of different types of motor a c -

tivity (Chase, Sutton, and Rapin (1961)). According to Awazu (1965) rhyth-

mic visual and acoustic stil~lulatioiis increase the physiological t r emor ,

whereas i r regular stimulation causes depression of the physiological t remor.

- -

$5 ''Slide" means a smooth syllable prolongation (Sheehan (1970)).

STL-QPSR 2 -3/1971 17. I i i I

It may be of interest to study this problem in more details, and we will 1 f i r s t examine singing. In relating speech and singing, it i s important to note

I I

that the speech melody of stutterers i s generally inflexible. The stutterers

speak monotonously (von W eichmann and Richter ( 19 66)), exhibit a poorer

rate of speaking, speak with greater force o r straine, and a r e judged to use I

l e s s rhythmical speech than the nonstutterers (Wendahl and Cole (196 l)),

whereas in singing vowels a r e prolonged and the phonation more continuous.

Accordingly, the movements of the articulatory muscles be come slower and

easier to control. The more continuous phonation when speaking in chorus,

singing, or "slidingW is, according to the author of this study, the cause of

the improvement of the stuttering symptom in these situations. I The effects of DAF and white noise will now be discussed in more detail.

I

According to many authors (see e. g. Stromsta (1956), stensland (1966), I

Beech and Fransella ( 1968), and Burke (197 1)) , which have investigated the

effect of DAF on normal speakers and stutterers, stutterers have an auditory

central nervous system disorder. But the results which have led to that hypo-

thesis a r e not very significant and the hypothesis i s strongly rejected by

many other authors, e. g. Gregory (1964) and ~ a n g o v 5 and ~ o r 6 v e k (1969).

In connection with the view that the cause of stuttering is anxiety, i t i s rele-

vant to note, that Dinner stein and Lowenthal (1 966) mentioned that one pos - sible way in which anxiety disrupts a mode of normal behavior should be the

producing of an increased latency in the perceptual systems which govern

that behavior. According to my opinion i t i s likely that the effect of DAF

and white noise can be explained a s an effect on the tremor amplitude, but

further inve stigations in this field a r e needed.

But how can we explain this interaction be tween stuttering, auditory

stimulation, and t remor? The mechanisms determining the amplitude of

physiological tremor a r e obscure. However, these mechanisms may in-

clude a common pathway through which the changes in tremor characteristics,

due to s t ress and auditory effects, a re mediated. A great deal of the stut-

tering therapy which is given today is psychologically oriented. In this con-

nection i t i s important to underline that emotional manife stations a r e thought

to initiate in the hypothalamus. Psychologically oriented therapy could ac - cordingly affect the hypothalamic areas , providing a connection link between

neurological and psychological fields (Kraft (1969)). The exaggerated ex-

cre tion of adrenaline could be caused by the emotional stimulation of the

INPUT STIMULUS

A B -Tertiary projection area for auditory input

(not st imulus specific)

Emotions Environment e sensations /' o v i s i o n I \ Secondary projection area

for auditory input (Brodmann's areo no.42;

Cortex stimulus specific )

It Primary projecting area for auditory input (Brodmann's area no. 41; stimulus specific)

Abstrqction (Censor )

50 ms \- K\nes*eii~ o p p ~ O t U s e

of

1 ects and Toctud ,t the m OW 'peec<p~eticular formation orient~tifln Dorsal and ventral cochlear \ nuclei; f i r s t synapse

I ' I Medulla oblongata ;-."I - Cronial n e r d s

---------- 4' & ~ d k n a l medulla Motor s ~ e e c h a ~ ~ a r a t u s

+-------' Auditory nerve 'I'

Muscles . .

4' Bone conduction 3 Cochlea S pe e c h ------------- Air conduction ?' , Outer ear

Fig. I -A-15. Feedback model of the speech production. (Based in part on Calby ( 1970) and Fibiger ( 1971a). )

Normal fluent speech production .I)--- ----.I---- & Stutte ring

STL-QPSR 2 -3/197 1

It i s hoped that this paper may add to a better understanding of the nature

of stuttering. However, much m o r e r e search i s needed, especially with r e - spect to the interaction between t remor and auditory stimulation. A better

understanding of the nature of stuttering i s of basic importance for an im-

proved stuttering therapy. One possible outcome of this study i s that the

r e sea rch of therapy of the overt symptom of stuttering may be concentrated

within the r e sea rch field of the t reatment of t remor .

Summary

The facial muscle s a r e studied ele ctr omyographically in speech situa-

tions a t s tut terers . It has been found that during stuttering there i s a physio-

logical (normal) t r emor with an exaggerated amplitude in the articulatory

muscles . It has further been found that phonation o r phonatory attempts in-

hibit the t remor . The author concludes that the overt symptom of stuttering

i s precisely a physiological t remor in the motor speech apparatus with an

exaggerated amplitude, induced indirectly because the speech situation i s a

s t r e s s situation for the s tu t te rer , and more directly by the increased ad-

renaline excreation. The findings a r e discussed generally, inter alia in

connection with neurophysiology, adrenaline secretion, and emotional s t r e s s .

Acknowledgments

The author i s deeply indebted to Prof. G. Fant and Dr . R. Leander son

for valuable advice, to Tekn. lic. J. Liljencrants for the construction of the

EMG-amplifiers, to the Central Neurophysiological Laboratory (head: Prof .

L. ~ i d k n ) a t Karolinska Sjukhuse t for applying the EMG-ele ctrode s , and

finally to the Laboratory for Clinical S t r e s s Research (head: Dr . L. Levi)

for applying a Grass Polygraph.

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1

STL-QPSR 2 -3/197 1 21.

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