ARTICULATORY DYNAMICS IN STUTTERING

DEVI T.R 2nd MSc SLP

• Among the varied views regarding etiology of stuttering, few of them consider stuttering as an articulatory disorder.

• Evidence for this view comes from many studies that have found many articulatory abnormalities and errors in stutterers.

• Models have been proposed in this regard which try to explain stuttering as an articulatory disorder.

Zimmerman’s model of Breakdown: the Interaction of Information and Action

Zimmerman (1980) suggested that stuttering should be regarded as a disorder of movement and that the principles of motoric behavior be brought to bear on the problem.

The focus on parameters such as velocity, displacement and duration of movement and the coordination and timing between articulatory events was motivated by the possibility of relating these events to underlying neurophysiologic processes

Disfluent events are associated with particular patterns that preceded and followed them.

These findings led to the speculation about the association between disfluent events and aberrant activation of brainstem pathways that physiologically link the articulators.

Specifically, it was suggested that lower velocities and displacements and longer durations in the movements of stutterers are associated with processes that keep activation of BS pathways below “threshold” level during perceptually fluent speech.

Bernstein (1967) proposed that the onset of any movement is preceded by preliminary tuning of the excitability of all participating sensory and motor elements.

Tuning or biasing facilitates or inhibits the excitability of certain pools of motor neurons and thereby alters the relationships among groups of muscles and determines the kind of behavior they will promote.

Inco-ordination may occur when either tuning or triggering inputs are aberrant.

The excessive tension noted in some stutterers prior to speech, the aberrant position of articulators preceding oscillatory or tonic activity of the articulators and the fact that most stuttering occurs on initial gestures indicate that the period before speech movements may be a time in which aberrant inputs are likely to occur in stutterers.

The central commands for speech might exist as spatially coded targets, auditory targets or some hybrid.

Whatever the representation of the code, the commands must be executed to achieve the critical spatial temporal relationship necessary for intelligible speech. Temporal and spatial relationships of the articulators must be achieved through out a speech gesture and that the fluent movement patterns are dependent on such relationships.

These must be accomplished by the proper neuromotor input via the cranial nerve nuclei and motoneuron pools to proper muscles or muscle system at the proper time.

The movements involved in achieving these goals, the contacts made and the positions achieved results in stimulation of many intraoral and perioral receptor sites.

It is posited that when a person speaks, he usually operates the respiratory laryngeal and supralaryngeal systems within certain ranges of variability i.e. he usually stays within certain limits in velocities, displacements, accelerations and inter articulatory spatial and temporal relationships.

For e.g. though the lower lip and jaw move more or less simultaneously toward given targets, (some normal variation occurs in lip jaw synchrony). When these normal ranges are exceeded the afferent nerve impulses generated are presumed to increase the gains at associated brainstem reflex pathways.

• If excitation reaches a “threshold level”, then oscillation or tonic behaviors occurs.

• Such reflex connections have been shown to disrupt the ongoing pattern behavior by altering afferent input and changing muscle length and tension which affect the gains and phases of these pathways.

If the velocity and displacement and the spatial relationships remain below “threshold levels” of variability so as not to increase reflex affects, fluent production occurs, the stability and integrity of the system is maintained, the visual feedback mechanisms are employed and the speech processes continue.

Stuttering as a defect in a coarticulatory timing (Van Riper):

Van Riper (1971) defined a stuttering behavior as a “word improperly patterned in time and the speakers’ reaction thereto”.

Van Riper hypothesized that the stability of motor patterns which maintain the integrity of syllables is somehow lacking in stutterers due in part to over-reliance on auditory feedback for speech control instead of appropriate monitoring via tactile kinesthetic proprioceptive feedback.

In addition, stutterers are thought to be deficient in their ability to “time” or integrate long motor sequences. Such “timing” is said to involve the imposition of higher order integration to achieve the proper serial order of a large number of discrete motor sequences.

A dominant movement, such as stressed syllable, is what typically “times” a speech sequence up to phrase in length. Stutterers are intermittently unable to achieve such “timing” thereby producing sequences within appropriate co articulation.

Van Riper also ruled out organic deficiencies in this speech related functions (underlying physiological difficulties). So, stuttering, he held is the result of deficiencies in:

• The stability of motor patterns for syllables• The ability to integrate a large number of

discrete events in correct temporal order and • Speech related respirations, phonation and

articulation

The combined result of these short comings is fractured syllables characterized by improper coarticulatory transitions between sounds.

For e.g. early stuttered repetitions of CV syllables often contain the schwa vowel instead of the target vowel (e.g. /s∂-s∂- - sop/.)

In such repetitions, it appears that the stutterer is searching for the appropriate coarticulatory features for the sound(s) he is attempting to say.

When the correct features are achieved, the stuttering is terminated

In other stuttering movements, precise timing of transitional events between sound is often lost due to breaks in airflow, excessive tension and inappropriate postures.

Agnello also said that “the primary feature of stuttering is essentially within the articulatory transition from phone to phone.

Reason for these lacks of transitions lie somewhere higher in the vocal tract resulting in excessive supraglottal air pressure and causes phonatory difficulties.

Van Riper’s model or stuttering as a defect of co-articulatory timing is not concerned with most of linguistic determinants.

Van Riper’s model i.e. a defect in timing may explain some of the problems stutterers have in maintaining rhythmic repetitions of various speech and non-speech tasks.

Articulatory Errors:

It can be studied under 2 broad headings.

A. Temporal errors:

B. Spatial errors:

A. Temporal errors: • Longer phoneme durations• Shorter phoneme durations• No significant difference• Longer durations between articulatory events• Inaccurate timing

B. Spatial errors:• Spatially restricted movements • Inappropriate articulatory placements• Excessive articulatory movements• Static positioning of articulators • Forceful articulatory patterns• Low velocities of articulators• Reverse muscle movements• Difficulty in stabilizing the articulatory movements

Temporal Errors:

Longer Phoneme Duration:

Several studies have revealed increased phoneme duration in stutterers.

Disimoni (1974)

• 6 stutterers with age Ranging from 18 to 39.

• Stutterers had significantly greater absolute vowel and consonant durations than the non-stutterers (NS).

Montgomery and Cooke (1974) • Studied part word repetitions in the speech of

adult stutterers using Spectrography• Results indicate that longer consonant duration in

the initials segment of Stuttered word.

Prosek & Runyan (1982) • Measured duration of stressed vowels;

extracted from connected speech using Spectrography.

• Results indicate that stuttering group spoke with more pauses and with longer average pause and vowel duration than Non-stutterers. Stuttering Group total duration of stressed vowel = 170.6 msec. Non-stuttering group total duration of stressed vowel = 144.1 msec.

Kalveram & Jancke (1989) Studied vowel duration under DAF condition Longer vowel duration in stuttering group reported.

Revathi (1989)• 2 normally nonfluent and 2 stuttering children

using spectrographic analysis for vowel duration .• Results indicate that stuttering group children had

significantly longer vowel duration than normal nonfluent group.

Shorter phoneme duration: A few authors have reported contradicting

results compared to the previously quoted studies.

1.Reimann (1976) studied context dependence of vowel duration in German words.

• Results:• Stuttering group had shorter vowels than

controls. Also stuttering group altered the vowel duration depending on the consonant that followed (similar to normals).

2. Production of vowels by stuttering children and teenagers.

Howell, Williams & Young (1991)

Purpose:• To analyze the acoustic properties of vowels in

children’s syllable repetition to establish whether there are differences between children and adults which might be indicative of the early characteristic and progress of the disorder.

Method:• 24 children and 8 teenage stutters• Recorded 10 min duration sample• From instances of syllable repetition – those which

started with voiced plosives and where final repetition included a part of the vowel was chosen.

Acoustic analysis of speech waveforms for – • Formant frequency• Duration • Intensity• Excitation source information

Results:• No marked differences between the formant

frequency between 2 groups, indicating that both groups position the supra glottal articulators in an equivalent positioning order to produce the intended vowel, whether spoken fluently or dysfluently.

• Duration of children’s stuttered vowels are short in comparison with those of fluent vowels of teenagers.

• No difference in intensities for fluent Vs. dysfluent vowels in children, but in teenagers, fluent vowels were higher in intensity than the dysfluent vowels.

•

• Marked differences between excitation applied to VT between dysfluent and fluent vowels between both age groups.

• They suggest a thorough appreciation of the properties of this component of vocalization may be important in understanding how stuttering develops.

No significant differences:

A few authors have reported no significant differences between stuttering group and non-stuttering group in phoneme duration.

1)Spectrographic Study of Vowels in Stutterers' Fluent Speech.

• Richard J. Klich Gaylene M. May; Journal of Speech and Hearing Research Vol.25 364-370 September 1982.

Method: • Measurements were made of the formant

frequencies and formant transitions associated with the vowels/i/,/æ/ and /u/ produced by seven moderate-to-severe stutterers when they read fluently in a control (normal) condition and under four experimental conditions: masking noise, delayed auditory feedback, rhythmic pacing, and whispering.

Result: • The first and second formant frequencies in an

isolated/hVd/context were more centralized than those reported for nonstutterers. The formant frequencies were centralized even more in reading, but varied little across conditions despite

changes in fluency, speaking rates, and vowel duration. Duration and rate of formant transitions also were essentially the same across conditions.

Conclusion:• These findings indicate that stutterers' vowel

production is more restricted, spatially and temporally, than nonstutterers'.

2) Acoustic Measures of Stutterers' and Nonstutterers' Fluency in Two Speech Contexts

E. Charles Healey., Peter R. Ramig; Journal of Speech and Hearing Research Vol.29 325-331 September 1986.

Aim: • The purpose of this study was to compare

stutterers' and nonstutterers' fluency during multiple productions of two dissimilar speech

contexts. Twenty-two adult stutterers were matched within 1 year of age to 22 nonstutterers.

Method:• Spectrographic analyses were performed on

subjects' five consecutively fluent productions of a simple isolated phrase and a phrase extracted from an oral reading passage. Measures of fluent voice onset time (VOT), and vowel, consonant, and total phrase durations were calculated from the five repetitions of each phrase.

From the isolated phrase, there were a total of five fluent durational measures (i.e., one VOT, two vowel, one consonant, & one phrase duration). For the phrase taken from the oral reading passage, six fluent measures were obtained (i.e., one VOT, three vowel, one consonant, & one phrase duration).

Results: • Results demonstrated that only one of the five

measurements taken during the isolated phrase condition was significantly different between the groups. Three of the six measures obtained from the phrase taken from the oral reading condition revealed significant between-group differences. No group differences were associated with the repetitions of either phrase for any of the dependent measures for both groups.

Conclusion: • These findings suggest that the length and

complexity of the speech tasks used to obtain acoustic measures of stutterers' fluency play an important role in the discovery of differences between the fluency of the two groups.

•

Longer duration between articulatory events:

• It is the period of inactivity between two consecutive articulatory gestures. Adams et al. (1975)

• Healy et al. (1976) reports of longer duration between articulatory events in stutterers.

Inaccurate timing:’

Timing Control Accuracy in Normal Speakers and Stutterers. Margaret H. Cooper; George D. Allen., Journal of Speech and Hearing Research Vol.20 55-71 March 1977.

• Cooper & Allen (1977) studied speech timing control accuracy of S and NS group during speech and non-speech activities.

Purpose:• This study attempted to assess the abilities of

10 normal speakers, five stutterers in therapy, and five stutterers no longer in therapy, to control the time program of repeated utterances.

Method:• The speech sample comprised of repeated

sentences, paragraphs, and nursery rhymes. • Temporal accuracy was measured.

Results: Results suggest that

• (1) there is a wide range of timing abilities, even among the normal speakers, with considerable overlap between the different groups of speakers;

• (2) on most of the experimental tasks, normal

speakers are more accurate timers than are stutterers;

• (3) stutterers released from therapy are more accurate timers than are stutterers still in therapy, whenever these groups differ.

Spatial errors:

Spatial errors investigated are:• Spatially restricted movements • Inappropriate articulatory placements• Excessive articulatory movements• Static positioning of articulators• Forceful articulatory patterns• Lower velocities of articulators• Reverse muscle movements• Difficulty in stabilizing the articulatory movements

Spatially restricted movements:

It has been reported that the stutterer’s articulatory movements are spatially restricted with the velocity and the direction of movement altered.

Zimmerman (1980)• Used high speech cineradiography to describe

kinematics and spatial and temporal organization of the perceptually fluent speech gestures for 6 stutterers and 7 non stutterers. He analyzed movements of lower lip and jaw in CVC /mam/, /pap/, /bab/.

• Results revealed that Even in perceptually fluent utterances, the organization of events necessary for speech production differs between groups of stutterers and nonstutterers.

Klich & May (1982)• Studied formant frequency and rate of formant

transitions of vowels in adult stutterers• Results revealed temporally and spatially

restricted vowel production.

Inappropriate articulatory placements:• Studies done by the following authors reveal

that the articulatory movements in stuttering groups are inappropriate.

Zimmerman • Used high speed cineradiography to describe

kinematics and spatial and temporal organization of the perceptually fluent speech gestures for 6 stutterers and 7 non stutterers. He analyzed movements of lower lip and jaw in CVC /mam/, /pap/, /bab/.

• He found stutterers having Asymmetry between lip and jaw movements leading to inappropriate articulation.

Van Riper (1982)• Stuttering as a temporal disruption of the

simultaneous and successive programming of muscular movements required to produce a speech sound or its link to the next sound in a word.

• Based on spectrographic and cineflourographic analysis, he suggested that during repetitions, highly inappropriate articulatory postures may be used; both in voiced and unvoiced sounds.

Mohan Murthy (1988) • Studied acoustic aerodynamic and laryngeal

correlates of stuttering.• Spectrographic analysis indicated articulatory

fixations followed by inspiratory frication.

Excessive articulatory movements:

Shapiro (1980) did an extensive study and measured EMG activity of Orbicularis Oris, superior longitudinal and intrinsic laryngeal muscles of fluent and dysfluent speech of stutterers.

Results:• Excessive muscle activity during production of

fluent as well as non-fluent utterances.• Inappropriate bursts of activity before and during

periods of silence in both fluent and dysfluent utterance.

• Lack of muscle coordination during periods of blocks, whose normal function is reciprocal action.

These findings strongly suggest that stutterers while speaking, experience many movements of disruption of normal coordination.

Depending on number of factors including its nature, intensity, duration and timing of disruption its effect may or may not result in audible or perceptible stuttering.

In some cases, disruption occurring at the onset of a word may simply result in

• a slight delay in word initiation or• a pause, too brief to be identified as dysfluency

In some other cases, the only result may be a

• shift in F0

• a voicing break• fry phonation, or• abnormally long onset time

Static Positioning of Articulators:

Zimmerman (1980) & Pindzola (1987)• Stutterers articulator stay in static position during

the production of a phoneme.

Zimmerman (1980)• Used high speed cineflurographic technique to

record articulatory movements during fluent and dysfluent speech from 4 stutterers and control utterances from one normal speaker.

• Interarticulator positions occurring in both perceptually fluent and dysfluent utterances of stutterers were unlike those in fluent utterance of a normal speaker. Aberrant interarticulator positions preceded repetitive movements and static posturing.

Pindzola (1987)• Reported that stutterers spend longer time

in static articulatory position. In other words, the duration of steady state formant was found to be longer in stutterers.

Forceful articulatory patterns:

• Webster (1974) suggested that stutterers use articulatory patterns that are too forceful and coarticulatory movements that are too rapid.

Lower velocities of articulators:

Studies done by various authors (Adams et al. 1975), Healy et al. (1976) & Zimmerman (1980) have revealed lower velocities of articulators in stutterers.

• Zimmerman (1980) used high speed cineradiography to describe the kinematics and spatial and temporal organization of perceptually fluent utterances of 6 stutterers and 17 normal speakers.

• Results: Lower peak velocities of articulators in stutterers.

•

Correlation of stuttering severity and kinematics of lip closure

• Michael D., McClean., Kroll., Loffus, (1991)

Stutterers and nonstutterers differ in orofacial movements associated with perceptually fluent speech, however inconsistent results have been obtained in this area.

Presence of some evidence that parameters of stutterers fluent speech are associated with stuttering severity, encourages one to use correlation or regression analyses as approaches to understanding anomalies in the movement characteristics of stutterer’s fluent speech.

Aim:

• To evaluate possible relationship between stuttering severity and parameters of lip and jaw movement associated with lip closure in fluent speech.

Method:• 17 adult stutterers (17-44 years); no speech

therapy since last 3 years of the time of testing.

Severity rating: By SLPs perceptually through 285 word passage and conversation. Also, % words stuttered, and average duration of the 3 longest dysfluencies (reading and conversation samples).

Movement recording and analysis:• Head mounted strain system was used to

transduce upper lip (UL), lower lip (LL) and jaw displacement. Word “Sapapple” ws stimulus

Results:

• Parameters analyzed: velocity, duration, displacement

• Tendency for more severe stutterers to show: – Longer movement durations– Reduced movement velocities

Because the fluent utterances were judged, interpretation is that the more severe stutterers achieved their fluency by executing motor compensations similar to those acquired during speech therapy. This may have involved adjustments in movement duration and/ or velocity.

Reverse muscle movements:

Study done by Guitar et al. (1988) details the muscle activity of 2 muscles depressor anguli oris (DAO) and depressor labii inferioris (DLI).

Method:• Examined lip muscle activity during the speech

production of stutterers and normal fluent speakers.

• Action of the above muscles were recorded using hooked were EMG.

• Word “peck”, “puck”, “puch”

Result: • EMG records indicated nonstutterers activated

DAO prior to DLI for the production of initial /p/, whereas, stutterers reversed the sequence of onset, particularly when they stuttered.

Conclusion:• This onset reversal in stutterers supports the view

of stuttering as a disorder of timing. As these reversed onsets are disruptions of the succession of DAO and DLI. The release of the sound may be delayed until the DAO activity is predominantly over DLI activity and hence it depicts an error that leads to a delay in the production of the sound.

•

Difficulty in stabilizing the articulatory movements:

Jansen et al. (1983) Investigated the difference between stutterers and normal speakers in phonatory and articulatory timing during the initiation of fluent utterances of monosyllabic words. EMG recordings of 4 articulatory muscles – glottal vibration recordings.

Subjects: 155 S and 17 NS

Parameters analyzed• Average interval between voice onset and onset of

EMG activity• Onset of EMG activity in each articulator • Intrasubject variability of above measures

Results: • No significant difference between S and NS in

average interval times and that stutterers in general were significantly more variable in their speech onset timing.

Conclusion:• Stutterers may have difficulty in stabilizing the

articulatory movements and the act of speaking results in fluctuations in the speech of production of sounds and sound sequences.

Rate and Rhythm of voluntary articulatory movement:

• A number of early studies investigated stutterers’ abilities to produce rapid speech or speech muscle movements (diadochokinesis) or rhythmic speech movements (rhythmokinesia).

Spriesterabach (1940) found no statistically significant differences between stuttering and nonstuttering subjects in maximum rate of jaw opening, tongue protrusion, and lip closure. Experimental subjects were slightly superior in jaw and tongue movements but slightly inferior in lip movements.

Strother & Kriegman (1943) also found stutterers’ diadochokinetic rates slightly (but insignificantly) higher for jaw openings, repeated /i/ productions (tongue tip to alveolar ridge), and lip closures. By contrast, Rickenberg (1956) found that stutterers were significantly slower than controls in repeatedly uttering consonant vowel (CV) syllables (/pa, ba, ma, ta, da, na, ka, ga, na/).

Rhythmic execution of jaw, tongue and lip movements was investigated by Blackburn (1931), and Seth (1934) (except tongue movements). These three investigations showed significant differences favoring nonstutterers.

Studies by Wolff (1935), Strother & Kriegman (1944), however found no significant differences between stutterers and nonstutterers on these tasks. Uttering repetitive /pataka/ sequences.

Zaleski (1965) found stuttering children deviated significantly more from a prior metronomic stimulus than nonstuttering children.

Bloodstein (1944) & Johnson (1961) reported slower than normal reading rates in adult stutterers, an unsurprising result considering the fact that it takes time to stutter.

Johnson & Rosen (1937) found that instructing stutterers to read faster than normal resulted in more stuttering and slower than usual in less stuttering.

Fransella (1965) also found that stuttering was reduced when subjects were asked to reduce their reading rates.

Ingham, Martin & Kuhl (1974) assessed the effects on stuttering in spontaneous speech of speaking slower and faster than normal in three adults stutterers. By means of a series of lights, subjects were given feedback every minute regarding how successful they were in either speaking more slowly or more rapidly than baseline rates. The procedures were effective in reducing speech rate in all three subjects.

• Zinkin (1968) studied cineflurographic films of the pharynx taken during stuttering and reported considerable lack of coordination between pharyngeal and other articulatory movements. Instances were observed in which pharyngeal movements were relatively fixed while other articulators moved. The converse was also observed, that is, examples of static articulatory gestures were observed during periods of pharyngeal movement.

•

Coarticulatory Errors:

• A number of studies have focused upon coarticulatory characteristics of stuttered speech co articulation refers to the normal phenomenon during speech hereby the production of a given sound is influenced by other sounds which occur before and after the sound in an utterance. Abnormal transitional movements first described by Stromsta (1965).

• Various studied are:….

Abnormal formant transition:• Presence of abnormal formant transitions

has been indicated in several studies.• Stromsta (1965) demonstrated that the

spectrogram of stuttered speech revealed a lack of usual falling or rising transitions seen in the spectrograms of normal speakers. The juncture formants were either absent or different.

•

• He also added that these children whose dysfluencies showed anomalies in co articulation failed to outgrow their stuttering, and those children whose spectrograms showed normal juncture formants had become fluent in the ten years span since the original recordings were made.

Adams & Reis (1971)• Investigated the difference in the frequency of

dysfluencies of voiced and voiceless phonemes in stutterers.

• Stated that increased stuttering is more likely to occur during voiceless voiced phonation transition than voiced voiceless transitions. They hypothesized that if the larynx was an important site in the break down of fluency, then conditions requiring increased laryngeal adjustment would create an increased frequency of stuttering.

Angdlox et al. (1974)• Analyzed spectrograms of the stutterer’s speech• He concluded that stuttering dysfluencies did not

show the normal downward shift of the 2nd formant associated with normal articulatory positioning.

Webster (1974)• Compared stutterers and non stutterers• Stutterers use rapid coarticulatory movements.

• Montgomery & Cooke (1976)• Analyzed perceptually and acoustically carefully

selected set of part word repetitions from the speech of adult stutterers.

• Spectrographic analysis revealed the abnormal or formant transitions characterized the initial segment of the stuttered word and the remainder of the word was identical to its fluently produced counterpart. From this they have concluded that if the articulatory breakdown was confined to the initial consonant and it was likely that abnormal formant transitions from initial consonant to vowel, when present were due to deviant formation of consonant rather than to faulty transition dynamics.

Manning & Cautal (1987)

• Investigated the dysfluencies during voiced – voiced, voiced-voiceless, voiceless-voiceless phoneme to phoneme phonatory transitions. Speech of 11 adult stutterers and a matched group of non-stutterers were studied.

• Both stutterers and non stutterers group demonstrated a lower percentage of dysfluencies during voiced-voiced transitions than during voiced-voiceless, voiceless-voiced and voiceless-voiceless phonatory transitions.

Revathi (1989)

• Studied acoustic temporal parameters in the speech of two normally nonfluent and two stuttering children.

• Spectrographic analysis revealed that transition duration of F2 and speed of transition of F1 showed a significant difference between stutterers and non-stutterers.

2 Extent of formant transition Suchithra (1985)

• Studied coarticulatory effects influent utterances of stutterers and compared it with the normal speakers.

• Results indicated that though the rising and falling trend of the formant frequency transition was the same in the speech of stutterers, as it is in normal speech. The extent is different in two groups i.e. articulatory configuration for the production of a phoneme in question was not fully achieved (stutterers are slowest in completing the transition)

Other errors observed were: (by Raghunath, 1992)

a) Lack of formant transition• The spectrogram of some dysfluent

utterances were characterized by absence of formant transition. This indicates stutterers are unable to transit or move from one phoneme to another.

b) Longer transition duration• The transition duration of F2 was longer for

dysfluent utterances than the corresponding fluent utterances. This implies that the time lapse between the movement of articulator from one target to another is long (explains prolongation).

c) Shorter transition durations• I.e. shorter time lapse between movement

of articulators from one target to another (repetitions

No Significant difference in VOT:• Some studies have indicated no significant

difference between stutterers and non-stutterers for VOT value.

• Brenner et al. (1972)• Metz et al. (1979) spectrographic analysis• Borden et al. (1985) EGG and acoustic analysis• Zebrowski et al. (1985) acoustically analyzed• Revathi (1989) acoustic temporal parameters in

the speech of 2 normally fluent and 2 stuttering children. Spectrographic analysis revealed no significant difference between stutterers and normally nonfluent for VOT.

Acoustic analysis of young stutterers and non-stutterer’s disfluencies (Healey & Bernstein)

Aim:• To identify and describe the acoustic features

of the disfluencies of preschool age children that represent excessive tension of laryngeal behavior.

• To compare vocal FO patterns of similar disfluencies (i.e. phrase, whole word and part word repetitions) between preschool age children who were diagnosed as ‘stutterers’ by an SLP and those who were considered normally fluent by parents and a clinician.

Method:• Subjects – 2 groups • 1 group 5 male stutterers (2.8 and 4.9 years)• 2 group 4 male children (3 – 4.9 years)• Tested and classified as normally nonfluent• Sample recording “free play”• Random sample of similar fluencies were

taken for analysis – PW, whole word and phrase repetition.

• Fed into computer for acoustic analysis• Intonational plots as well as print out of the

individual F0 values were obtained. F0 mean, SD and range in Hz and semitones were calculated.

Results:• Reveal that there are no significant differences

between stutterers and non stutterers F0 mean and F0 variability for disfluent segments within a part word, while word or phrase repetition. The same was found for perceptually fluent segments.

Conclusion:• These findings support the notion that the

speech disfluencies of young stutterers and normally fluent children are not categorically different, at least, in terms of the vocal frequencies and accessibility exhibited ruing a disfluent movement.

• Moreover, the disfluent segments within the PW, WW and PR did into alter the phonatory features of the perceptually fluent words adjacent to those disfluent utterances.

•

Kinematic Studies: • There are some studies which examines the

kinematic correlates in stuttering.

Zimmerman & Hanley (1983)• Examined the effects of fluency enhancing

procedure, the adaptation effect produced by repeated reading of a passage in three adults who stutter using EMMA.

• They found no evidence to support the hypothesis that reduced amplitude and velocities of articulatory movement were characteristics of fluent speech of adults who stutter.

Story Alphonso and Harris in 1996• Assessed Articulatory dynamics using EMMA in

three adults who stutter pre and post treatment with the Holliens precision fluency-shaping program

• The fluent speech of these adults post treatment was produced with lower displacements and velocities compared to pre-treatment measures.

Caruso, Abbs & Gracco in 1988• Sequencing of peak velocity of upper lip lowerlip

and jaw movement was reduced in adults who stutter compared to normally fluent speakers. But later studies by DeNeil, 1995; McClean, Kroll & Loftus in 1990 failed to replicate this findings.

McClean et al. 1990• Fluent speech of stuttering and non stuttering

adults did not differ on any of 15 movement parameters, though stuttering adults who had been on an intensive treatment program did show longer duration between events.

McClean, Levandow Ski & Cord in 1994. • Also reported the absence of systematic

relationships between kinematics parameters and stuttering severity

Ward 1997

Ward employed a phase portrait analysis• Also failed to find differences between stuttering

adults on relative timing of articulatory peak velocity sequences and further reported that even at faster rates, adults who stutter did not show unusual sequencing patterns and phase angle variability was consistently greater in the stuttering group and that the greatest phase angle variability was observed at fast articulatory rates and when altered stress patterns were required.

Formant Frequency Fluctuation In Stuttering And Nonstuttering Adults

Michael Robb, Michael Blomgren, And Yang Chen

Inferences were made regarding the vocal tract stability of stutterers’ and nonstutterers’ fluent speech through the examination of formant frequency fluctuation (FFF).

Fifteen adult males served as subjects comprising separate groups of untreated stutterers, stutterers enrolled in a fluency-shaping treatment program, and nonstuttering controls.

The steady-state portion of formant 2 (F2) was examined in the production of various CVC tokens and evaluated by examining the absolute Hz difference in F2 across consecutive glottal periods.

Results of the acoustic analysis indicated a trend in FFF across the three groups.

The untreated stutterers displayed the greatest FFF, followed by the control group, with the treated stutterers displaying the most F2 stability.

• Data regarding formant transitions in the dysfluent speech of children and adults indicate that the pattern of second formant (F2) transitions is variable.

• The F2 transitions are sometimes absent or atypical (Howell & Vause, 1986;Stromsta, 1986; Yaruss & Conture, 1993), and when they are appropriate they tend to be short in duration (Yaruss & Conture, 1993).

Abnormal F2 transitions have also been observed in the perceptually fluent speech of stutterers (Howell & Vause, 1986; Robb & Blomgren, 1997, Zimmermann, 1980).

Although past studies vary with regard to analysis methods and speech samples,they seem to confirm that individuals who stutter experience difficulty transitioning from one speech sound to the next.

In accord with these findings, treatment approaches that address smooth, deliberate articulatory transitions have shown improvements in speech fluency (e.g., Webster, 1975).

The authors found clear differences between groups for cycle-to-cycle variations in both frequency (jitter) and amplitude (shimmer).

The differences in F0 perturbation were thought to reflect difficulty by the stutterers in maintaining a fixed laryngeal posture during vowel steady-state production.

The Newman et al. (1989) findings concerning differences between stutterers and nonstutterers in the laryngeal behavior (i.e., F0 perturbation) of their steady-state productions would suggest that differences may also be apparent in the supralaryngeal (e.g., formant frequency) behavior characterizing vowel steady-states.

• The purpose of this study was to use a relatively unknown acoustic metric, formant frequency fluctuation (FFF), to inferentially evaluate vocal tract stability in the steady-state vowel productions of normally fluent and dysfluent adults.

• The measure is based on the premise that a change in vocal tract configuration can be measured as a temporal change in formant frequency.

• It was hypothesized that persons who stutter would differ from normally fluent speakers in the F2 stability of their vowel steady-state productions as a result of disordered motor steadiness within the vocal tract.

• To the extent that FFF serves as a measure of vocal tract stability, the present findings indicate that disordered articulation is also manifest in the steady-state portion of vowels.

Using refined methods of acoustic analysis such as FFF, it is becoming increasingly clear that the fluent speech of stutterers is more different than similar to that of normally fluent individuals.

Some Spectral and Acoustic Correlates of Stuttering: A pre- post Therapy Comparison

Santosh. M., AIISH., 2006.

This study investigated the efficacy of non-programmed prolonged speech technique in persons with stuttering. Subject’s reading, spontaneous speech/ conversation were recorded before and after and 6 months after non- programmed prolonged speech therapy. Percentage dysfluencies, type of dysfluencies, rate of reading and mean naturalness score, and temporal and spectral acoustic parameters were measured. Aerodynamic, laryngeal, and articulatory errors were also identified and classified as visualized on wide band spectrograms.

Results showed a significant decrease in percentage dysfluencies and rate of reading and significant increase in mean naturalness score from pre therapy to post therapy conditions in both age groups.

Speech Production Errors:• Different types of errors were identified and

classified as visible on wide-band spectrograms as respiratory errors, laryngeal errors articulatory errors and multiple errors.

Aerodynamic errors:• Production of aspirated for unaspirated phoneme:• Production of unaspirated for aspirated phoneme:• Inspiratory intake (II): represented by the noise

energy as aperiodic vertical striations in all freqs• Expiration: it was present between words starting

with retroflex stops and nasals depicted as noise energy spread all over frequencies

Laryngeal errors:• Production of unvoiced phonemes for voiced

phoneme:• Production of voiced phoneme instead of partially

voiced phonemes:• Substitution of partially voiced phoneme for voiced

phoneme or addition of partially voiced phoneme:• Cessation of voicing: characterized by complete

cessation of voicing depicted as absence of voice bars on the baseline of the spectrogram and indicates an open glottal gesture.

• Prolonged voicing:• Substitution of voiced phoneme by voiced

murmured phoneme for voiced phoneme.•

Articulatory errors:• Addition errors:• Addition of /a/ , /i/ , and Click

Place errors:• included substitution errors

Manner errors:• observed in initial syllable of dysfluent and fluent

utterances. Includes deletion of nasal, substitution of nasals for nonnasals and others

• Absence of F2 transition: absence of transition depicts inability to move smoothly from one phoneme to other.

• Prolongation• Cluster reduction: by addition of vowels between

the consonants

Multiple errors:• Manner + voicing error:• Substitution of unvoiced phoneme for voiced and

absence of F2 transition: • Manner error and absence of F2 transition: • Substitution of unvoiced phoneme for voiced

phoneme and cluster reduction: • Inspiratory intake + /a/ + absence of F2 transition.

Some acoustical, aerodynamic and laryngeal correlates of stuttering: pre-post therapy comparison.Mohan.Murthy.G, AIISH (1988)

A single case study on a 17 year old male stutterer. Speech dynamics during pre and post therapy utterances were studied and compared. Totally 29 dysfluent words were analyzed.

Perceptually dysfluencies were of 5 types.• Intra word audible pause• Intra word silent pause• Whole word repetition• Intra word repetition• Phoneme repetition and prolongation.

Wide band bar type spectrograms with average amplitude function were taken for the audio recordings. Segment duration and formant transitions were measured at the apparently disrupted instances.

Results revealed;• Inhalation frication of varying duration(50-260ms)

and spectral characteristics were present• Atypical CV and VC transitions of vocal fold cycles

were observed• Some paradoxical observations where larynx

tracing & voice bars on spectrogram did not correlate

• Inappropriate timing of voicing.• A clear pattern of longer or shorter post therapy

segmental durations were not evident.• Articulatory fixation during inhalatory frication• Abnormal articulatory constrictions for fricatives

were observed.

• Investigating speech motor practice and learning in people who stutter.

• Namasivayam AK, van Lieshout P.• Journal of Fluency Disorders. 2008

• In this exploratory study, authors investigated whether or not people who stutter (PWS) show motor practice and learning changes similar to those of people who do not stutter (PNS).

• To this end, five PWS and five PNS repeated a set of non-words at two different rates (normal and fast) across three test sessions (T1, T2 on the same day and T3 on a separate day, at least 1 week apart).

The results indicated that PWS and PNS may resemble each other on a number of performance variables (such as movement amplitude and duration), but they differ in terms of practice and learning on variables that relate to movement stability and strength of coordination patterns.

These findings are interpreted in support of recent claims about speech motor skill limitations in PWS.

Bite-block perturbation in people who stutter: immediate compensatory and delayed adaptive processes.

Namasivayam AK, van Lieshout P, De Nil L.

Journal of Communication Disorders. 2008

• This exploratory study investigated sensory-motor mechanisms in five people who stutter (PWS) and five people who do not (PNS).

• Lip kinematic and coordination data were recorded as they produced bi-syllabic nonwords at two rates (normal and fast) in three conditions (jaw-free, immediately after insertion of a bite-block, and after a 10-min accommodation period).

At normal speech rates, effects of bite-blocks on lip kinematics were similar for both PWS and PNS speakers showing larger amplitudes, peak velocities, shorter durations and more stable movement cycle patterns. However, at fast speech rates upper lip responses of PWS exhibited larger amplitudes and peak velocities. was found at normal speech rates.

At both speech rates, the presence of a bite-block changed movement coordination patterns only for PNS.

However, at fast speech rates bite-blocks decreased variability of coordination patterns for both groups.

No adaptive changes in movement stability were found for either group, but a practice-related increase in lower lip peak velocity

• These findings indicate that bite-block perturbation did not exacerbate any hypothesized limitation or difficulty in controlling individual articulatory movements or their coordination in PWS.

• The results also support the position that specific motor control strategies are used by PWS as compared to PNS to compensate for bite-block perturbations under increased speech rate demands.

Speech production in people who stutter: testing the motor plan assembly hypothesis.

• van Lieshout PH, Hulstijn W, Peters HF.• Journal of Speech and Hearing Research. 1996

The main purpose of the present study was to test the hypothesis that persons who stutter, when compared to persons who do not stutter, are less able to assemble abstract motor plans for short verbal responses.

Subjects were adult males who stutter and age- and sex-matched control speakers, who were tested on naming pictures and words, using a choice-reaction time paradigm for both tasks. Words varied in the number of syllables (1, 2, and 3 syllables) and, for the bisyllabic words, also in the number of consonants (one or more) at the onset of the second syllable.

Measurements consisted of speech reaction times, word durations, and measures of relative timing of specific motor events in the respiratory, phonatory, and articulatory subsystems.

Results indicated that, in spite of longer speech reaction times for persons who stutter in comparison to control speakers, there was no interaction with word size, a finding that does not lend support to the abovementioned hypothesis. Word durations were found to be longer for persons who stutter, and, in addition, there was an interaction of group with word size. Both findings were associated with longer delays for persons who stutter in the onset of upper lip integrated electromyographic (IEMG) activity and thoracic compression, and a group effect on the order of upper lip and lower lip IEMG onset.

• Findings are taken to suggest the possibility that persons who stutter may use different motor control strategies to compensate for a reduced verbal motor skill, and although the nature of this reduced skill is unknown, it is speculated that it relates to the processes involved in the integration of sensory-motor information.

Gestural overlap in consonant clusters: effects on the fluent speech of stuttering and non-stuttering subjects.

• Huinck WJ, van Lieshout PH, Peters HF, Hulstijn W

• Journal of Fluency Disorders. 2004

This study was designed to investigate if persons who stutter differ from persons who do not stutter in the coproduction of different types of consonant clusters, as measured in the number of dysfluencies and incorrect speech productions, in speech reaction times and in word durations.

Based on the Gestural Phonology Model of Browman and Goldstein, two types of consonant clusters were formed: homorganic and heterorganic clusters, both intra-syllabic (CVCC) and inter-syllabic (CVC#CVC).

Overall, the results indicated that homorganic clusters elicited more incorrect speech productions and longer reaction times than the heterorganic clusters, but there was no difference between the homorganic and the heterorganic clusters in the word duration data.

Persons who stutter showed a higher percentage dysfluencies and a higher percentage incorrect speech production than PWNS but there were no main group effects in reaction times and word durations.

However, there was a significant three-way interaction effect between group, cluster type and cluster place: homorganic clusters elicited longer reaction times than heterorganic clusters, but only in the inter-syllabic condition and only for persons who stutter.

• results suggest that the production of two consonants with the same place of articulation across a syllable boundary puts higher demands on motor planning and/or initiation than producing the same cluster at the end of a syllable, in particular for PWS.

Adaptation of stuttering frequency during repeated readings: associated changes in acoustic parameters of perceptually fluent speech.

• Max L, Caruso AJ.• Journal of Speech Language and Hearing

Research. 1998

This study is part of a series investigating the hypothesis that stuttering adaptation is a result of motor learning. Previous investigations indicate that nonspeech motor learning typically is associated with an increase in speed of performance. Previous investigations of stuttering, on the other hand, indicate that improvements in fluency during most fluency-enhancing conditions or after stuttering treatment tend to be associated with decreased speech rate, increased duration of specific acoustic segments, and decreased vowel duration variability.

The present acoustic findings, obtained from 8 individuals who stutter, reveal that speech adjustments occurring during adaptation differ from those reported for other fluency-enhancing conditions or stuttering treatment. Instead, the observed changes are consistent with those occurring during skill improvements for nonspeech motor tasks and, thus, with a motor learning hypothesis of stuttering adaptation.

• During the last of 6 repeated readings, a statistically significant increase in articulation rate was observed, together with a decrease in word duration, vowel duration, and consonant-vowel (CV) transition extent.

• Other adjustments showing relatively consistent trends across individual subjects included decreased CV transition rate and duration, and increased variability of both CV transition extent and vowel duration.

Speech motor correlates of treatment-related changes in stuttering severity and speech naturalness.

• Tasko SM, McClean MD, Runyan CM.• Journal of Communication Disorders. 2007

Participants of stuttering treatment programs provide an opportunity to evaluate persons who stutter as they demonstrate varying levels of fluency. Identifying physiologic correlates of altered fluency levels may lead to insights about mechanisms of speech disfluency.

This study examined respiratory, orofacial kinematic and acoustic measures in 35 persons who stutter prior to and as they were completing a 1-month intensive stuttering treatment program

Participants showed a marked reduction in stuttering severity as they completed the treatment program. Coincident with reduced stuttering severity, participants increased the amplitude and duration of speech breaths, reduced the rate of lung volume change during inspiration, reduced the amplitude and speed of lip movements early in the test utterance, increased lip and jaw movement durations, and reduced syllable rate. A multiple regression model that included two respiratory measures and one orofacial kinematic measure accounted for 62% of the variance in changes in stuttering severity.

Finally, there was a weak but significant tendency for speech of participants with the largest reductions in stuttering severity to be rated as more unnatural as they completed the treatment program.

Influences of length and syntactic complexity on the speech motor stability of the fluent speech of adults who stutter.

• Kleinow J, Smith A.• Journal of Speech Language and Hearing

Research. 2000

The purpose of the present study was to investigate the impact of utterance length and syntactic complexity on the speech motor stability of adults who stutter.

Lower lip movement was recorded from 8 adults who stutter and 8 normally fluent controls.

They produced a target phrase in isolation (baseline condition) and the same phrase embedded in utterances of increased length and/or increased syntactic complexity.

The spatiotemporal index (STI) was used to quantify the stability of lower lip movements across multiple repetitions of the target phrase.

Results indicated: (a) Adults who stutter demonstrated higher overall STI values than normally fluent adults across all experimental conditions, indicating decreased speech motor stability;

(b) the speech motor stability of normally fluent adults was not affected by increasing syntactic complexity, but the speech motor stability of adults who stutter decreased when the stimuli were more complex;

(c) increasing the length of the target utterance (without increasing syntactic complexity) did not affect the speech motor stability of either speaker group.

• These results indicate that language formulation processes may affect speech production processes and that the speech motor systems of adults who stutter may be especially susceptible to the linguistic demands required to produce a more complex utterance.

• The present findings, therefore, support the hypothesis that linguistic complexity is one factor that contributes to the disruptions of speech motor stability characteristic of stuttering.

From planning to articulation in speech production: what differentiates a person who stutters from a person who does not stutter?

• van Lieshout PH, Hulstijn W, Peters HF.• Journal of Speech and Hearing Research. 1996

The main purpose of the study was to differentiate between people who stutter and control speakers regarding their ability to assemble motor plans and to prepare (and execute) muscle commands.

Adult males, who stutter, matched for age, gender, and educational level with a group of control speakers, were tested on naming words and symbols. Group differences in muscle command preparation were assessed from electromyographic recordings of upper lip and lower lip.

Results indicated that they were significantly different in the timing of peak amplitudes in the integrated electromyographic signals of upper lip and lower lip (IEMG peak latency).

• Findings question the claim that people who stutter have problems in creating abstract motor plans for speech. In addition, it is argued that the group differences in IEMG peak latency that were found in the present study might be better understood in terms of motor control strategies than in terms of motor control deficits.

Jaw-phonatory coordination in chronic developmental stuttering.

• Loucks TM, De Nil LF, Sasisekaran J• Journal of Communication Disorders. 2007

A deficiency in sensorimotor integration in a person who stutters may be a factor in the pathophysiology of developmental stuttering. To test oral sensorimotor function in adults who stutter, authors used a task that requires the coordination of a jaw-opening movement with phonation onset. The task was adapted from previous limb coordination studies, which show that movement coordination depends on intact proprioception. They hypothesized that adult stutterers would show deficient jaw-phonatory coordination relative to control participants.

The task required initiation of phonation as a jaw-opening movement passed through a narrow spatial target. Target amplitude and jaw movement speed were varied.

The stuttering group showed significantly higher movement error and spatial variability in jaw-phonatory coordination compared to the control group, but group differences in movement velocity or duration were not found.

The aberrant jaw-phonatory coordination of the stuttering participants suggests that stuttering is associated with an oral proprioceptive limitation, although, the findings are also consistent with a motor control deficit.

Variations in the relative speeds of orofacial structures with stuttering severity.

• McClean MD, Runyan CM• J Speech Lang Hear Res. 2000

Stuttering can be characterized in part as a disorder in the coordination of different muscle systems. In light of basic aspects of orofacial physiology and development, the speeds of the lips and tongue relative to the jaw may be an important dimension for evaluating motor coordination among persons who stutter (PWS).

To test this idea, an electromagnetic system was used to obtain measures of lip, tongue, and jaw speed in 38 adults (29 PWS and 9 normally fluent speakers, NFS) as they repeated a simple speech utterance at a normal rate.

Using categorical ratings of stuttering severity, ratios of tongue speed to jaw speed were significantly greater in PWS rated as severe, compared to NFS and other PWS.

Significant increases in lower lip-to-jaw and tongue-to-jaw speed ratios with stuttering severity were also reflected in correlation analyses relating speed ratios to a continuous measure of stuttering severity.

These trends in speed ratio were related to increases in lower lip and tongue speed and decreases in jaw speed with stuttering severity.