stuttering and auditory functions .pdf / kunnampallil gejo

STUTTERING AND AUDITORY FUNCTIONS

KUNNAMPALLIL GEJO JOHN, BASLP, MASLP

KUNNAMPALLIL GEJO JOHN,MASLP

INTRODUCTION

What is stuttering?

Stuttering is the involuntary disruption of

a continuing attempt to produce a

spoken utterance.

PERKINS 1990


What is Auditory processing?

is the term used to describe the recognition &interpretation of a sound by the brain .

Learning to speak involves

. motor process of speaking

.sensory process of feeling .hearing oneself ,


Auditory processing in stutters

Researchers have suggested that,

stuttering may be the result of errors of

stutterers self hearing aspect ,

stuttering may have its origin because

of malfunctioning of the hearing

mechanism


Central processing in stuttering Hemispheric properties of stuttering

Brain waves of stutterers have

been examined &compared those with

non stutterers.

.CNS investigation suggested that

stutters lack cerebral dominance for

speech .


Lindshy &Freestone (1942) - stutters

demonstrate right hemisphere dominance

for language

o Wilkins EEG studies - final neural

dysfunction rather than hemispheric

differences in stutterers


Right hemisphere activity,

Fox (1996,2000) found decreased

activity in auditory area during increased

stuttering ,so reduces the left brain

communication of this sensory information

to frontal speech &language areas .


Research suggested that people who

stutter use Right hemisphere which leads

to intermittent break down

Why?

.Right hemisphere is not as adopt as the

left for processing rapid transmission

that characterizes spoken language


Right hemisphere is also associated with

emotional expression .

Excessive amounts of neurotransmitter

dopamine in the left caudate nucleus

(This is the area that translates speech in

to muscle movements ).There is no

conscious awareness of central auditory

processing in left caudate nucleus.


Left auditory cortex activity in stuttering

Many brain imaging studies of stuttering have shown a lack of activity in the left superior temporal lobe ,including auditory association areas & Wernicke’s area (FOX et al ,2000&DE NIL et al,2003).

suggest the possibility that when individual stutter they are not using auditory feedback to monitor & control their speech


Imaging study (SALMELIN et al ,1998) -

stutters have a reversal of the normal pattern

of activation of the left &right auditory

cortices during stuttering .

stutters may have difficulty performing

auditory processing tasks (BARASCH et al

,2000)

Fluency can be induced by changing the way

stutters hear their own speech (BRAYTON

&CONTURE ,1978;POWELL ,1987) KUNNAMPALLIL GEJO JOHN,MASLP

Auditory self monitoring may provide

a stimulus to time or integrate the sequence of activities that run in parallel when a speaker decides what she will say ,selects the linguistic elements for it ,and execute the utterance . Thus the dyssynchrony or timing disturbance are the basis of stuttering (Perkins,Kent,&Curlee,1991;Van Riper 1982)

may be caused by a paucity of signals that synchronize the sequence for speech output KUNNAMPALLIL GEJO JOHN,MASLP

Craver&Faber1982,Moore1986 found

that stutterers have poor recognition

&recall of words on auditory

presentations

Carpenter & Sommers1987 found

stutterers&nonstutterers have equal

auditory memory .


Auditory feedback closed circuits or cycles ,which have all

components completely contained with in

speakers mechanism .

The return flow of information provided by

these circuits helps to monitor our own

speech.

Errors are normally identified & corrected

automatically .


Closed loop system

CNS

MOTOR ACTIVITY SENSATION

FEEDBACK


System organizes in closely connected special & temporal units .

There will not be any time normal course for the speaker to pause & check the adequacy of the utterance after each word ,phrase or even after sentence uttered.

Hence ,speech once learned become self regulatory with satisfactory monitoring depends up on the proper functioning & integration of the of the all feedback circuits .


Fluency disruption as a cybernetic phenomenon:

Cybernetic theory holds that in a closed loop system ,various lines of feedback are used to regulate the output of a system .

The goal of such a system termed a servo system ,is to match what is intended as system output to the actual output and reduce any differences between the two (error signal) to zero .If there is distortion of the information arriving via the feedback loop , the error signal will be incorrect When this occurs the system tends to go into oscillation.


Fairbanks (1954)&Mysak (1960)described

the nature of such systems & interpreted

many aspects of speech production .

The basic idea is that in stutterers ,

distorted feedback creates the

misconception that an error has occurred

in the flow of speech .

Stuttering occurs when the speaker

attempts to correct an error that has in

fact ,not occurred


According to this phenomenon ,stutteres

posses a defective monitoring system

sequential speech

The studies shown that fluency breaks

similar in stutterers can be produced in

normal speakers by altering the auditory

feedback of their speech output .

From these findings the possible

existence of a perceptual disability in

stuttering is assumed probably organic in

nature KUNNAMPALLIL GEJO JOHN,MASLP

The influence of cybernetic theory (Weiner

1948) has led to number of hypothetical

models such as by Fairbanks

(1954)describe closed feedback ,loops as

the essential monitoring system for speech

Planum Temporale Abnormality and

DAF

(leftward asymmetry). A brain scan study

found that stutterers have the opposite:

(rightward asymmetry).


stutterers with this abnormal------ had

significantly improved fluency with DAF, but

stutterers with the normal leftward asymmetry

didn't improve with DAF.

The study also found that stutterers with this

abnormal ----stuttered more severely than

stutterers with the normal leftward asymmetry.

In adults with persistent developmental

stuttering and atypical PT anatomy, fluency is

improved with DAF.(Neurology 2004 Nov

9;63(9):1640-6.)


Altered Auditory Feedback Changing how stutterers hear their voices

improves fluency. This can be done in

many ways:

Speaking in chorus with another person.

Hearing a voice in headphones distorted

Hearing a synthesized sound in

headphones mimicking phonation

(masking auditory feedback, or MAF).


Hearing a voice in headphones delayed a

fraction of a second (delayed auditory

feedback, or DAF).

Hearing voice in headphones shifted

higher or lower in pitch (frequency-shifted

auditory feedback, or FAF).

These phenomena are called altered

auditory feedback


Nonstutterers can't tolerate altered

auditory feedback. Altered auditory

feedback increases blood flow to non-

stutterers' auditory/somatic integration

area, raising activity to an abnormally high

level.

The effects of too much activity in this area

are somewhat like stuttering—repeating

words and unexpected silent pauses.


Stuttering is reduced in many subjects by delayed,masked ,frequency altered feedback. Even amplified feedback may have some of the same power(JSHR,VOL42,910,1999)

The proportion of stuttering events prescribed telephone conversations were significantly reduced in the AAF conditions relative to the non-altered auditory feedback condition (JSLHR,VOL.40,1130-1134,1997) KUNNAMPALLIL GEJO JOHN,MASLP

DELAYED AUDITORY FEEDBACK

It refers to a delay in the return of the air

conducted speech signal to the central

auditory system.

it was reported by LEE(1950) …….coined the

term “artificial stutter” and commend on its

fluency disruption effects.

The most disruptive interval was found to be

in the 180-200 msec (Fairbanks & Guttman

1958:Ham &Steer1967) KUNNAMPALLIL GEJO JOHN,MASLP

(DAF) apparently degrades the individual’s

ability to self-monitor his or her ongoing

speech.

In the normal speaker, the introduction of

DAF via headphones breaks down the

speaker’s fluency, often producing

prolongation of vowels , slurring of

articulation & a marked interruption of

normal prosodic speaking patterns.


Conversely, in the stutterer, speech may

become more fluent under DAF, probably

related to the prolongation of vowels which

results in a general slowing down of

speaking rate

Slowing down the stutterer’s rate of

speech is often facilitative for improving

overall speech fluency.


Recommended Procedures for Using DAF

1. The selector mode on the Facilitator is

set to DAF (the letters DAF appear on the

instrument window). The loudness level of

amplification-DAF is determined by the

relative setting of the VOLUME switch


2. The relative time-delay on the Facilitator

ranges from .05 to 0.5 secs, with the

clinician able to control the delay-time by

increments of approximately 10 msecs .

3. Explain to the patient something like

this, "I want you to wear these

headphones as you read (or repeat) aloud.

What you say will be fed back to you on

the phones a bit delayed. You won’t be

able to hear yourself as you usually do

when you speak. Just keep speaking. I will

record on another recorder how you

sound." KUNNAMPALLIL GEJO JOHN,MASLP

4. After the initial testing on the effects of DAF on speech and voice, play the recorded output back to the patient. Depending on the effects of DAF, either go forward with more DAF practice or stop using it.

5. For those patients who profit from using DAF, it is recommended that the patient wear a portable Facilitator in the provided waist-pack. The DAF mode should be used whenever it appears to facilitate better speech or better oral reading.


AUDITORY FEED BACK TOOLS

AFT does not have visual displays. It is

designed to

focus clients on the aural characteristics of

their speech.


Pacer

The pacer provides metronomic pacing in

the form of an audible click to help assist

patients with the timing/rhythm aspects of

speech production.

Among these are stutterers and patients

with motor speech disorders such as

cerebellar ataxia and Parkinson’s disease.

The pacer rate is adjustable from


Delayed Auditory Feedback

as a form of disruptive feedback, which

has proven to be effective in fluency

therapy.

The DAF in AFT has a range of feedback

from 150-500 milliseconds.


Five Auditory Feedback Modes

Metronomic Pacing

Delayed Auditory Feedback (DAF)

Looping

Time-Warping

Masking


Looping Playback

Looping records the patient’s (or clinician’s)

speech and then plays the digitally recorded

speech back immediately.

used to develop critical self-listening skills.

Patients can hear their own speech just as an

outside listener would hear it.

The clinician or the patient can record the target

production. The absence of a visual display

helps the patient focus strictly on the auditory

aspects of speech.

The duration of the recorded speech is from 5 to

30 seconds, adjustable in one-second

increments


Time-Warping

Time-warping record a patient’s speech

and immediately play the speech back at

different rates without changing the

frequency content of the speech.

This is very useful for allowing patients to

hear their articulation clearly by slowing, or

increasing, the rate of playback


Masking

a speech-band noise signal is played

through headphones so that patients

cannot hear their own speech production.

This deliberately degraded feedback has

been shown, in some cases, to improve

speech. In many patients, it can enhance

the proprioception of speech/voice

behaviors (e.g., easy onset, eliminating

hard glottal attack, etc.).


Applications

The AFT program has a wide range of

applications in speech-language pathology

including voice, articulation, motor speech

disorders, fluency, aphasia, professional

voice, accent reduction, and learning

disabilities.


Delayed Auditory Feedback Most Helpful for Those Who Stutter with Atypical Auditory Anatomy

(American Academy of Neurology-) 2004

Researchers have identified a subset of

stutterers that may benefit most from DAF.

Findings of their study were DAF has

been shown to induce fluency in many

individuals who stutter, though not all

stutterers experience enhanced fluency by

this technique


The primary aim of the study was:

to learn if there is a relationship between

the anatomy of the auditory association

cortex (planum temporale) and fluency

induced with DAF in adults with persistent

developmental stuttering.


A study group of 14 adults with this type of

stuttering disorder and 14 control subjects

read prose passages three times: at

baseline, with non-altered feedback, and

with DAF.

Three measures of fluency were

evaluated: stuttering event frequency,

severity, and reading time.


" a subgroup of adults with atypical

rightward planum temporale asymmetry,

who were more dysfluent at baseline and

had fluency induced with DAF," (Anne

Foundas, MD,)

deficits in auditory processing cannot

account for stuttering in all people who

stutter, because we identified another

subgroup of adults who had typical

leftward planum temporale asymmetry and

who did not become more fluent with

DAF."


DAF in Stuttering: A Potential Anatomical

Link

DAF is a technique that can induce

fluency in individuals who stutter and can

make fluent individuals dysfluent

The auditory system, at least at the level

of auditory input, is involved in these

fluency inducing conditions


Thus, there may be a defect at the level of

auditory processing that is at least partially

reversed with these procedures.

One hypothesis is that alterations in the

auditory signal under conditions of DAF

diminish an auditory perceptual defect in

people who stutter.

This auditory perceptual defect might be

related to anomalous anatomy of auditory

temporal cortex. KUNNAMPALLIL GEJO JOHN,MASLP

Atypical anatomy in auditory temporal

brain regions (planum temporale, PT) in a

group of adults with persistent

developmental stuttering (PDS). (2000)

.Postulated that anatomic defect may be

functionally relevant, and the results of a

recent study suggest that there may be a

structure-function relationship.


In this study (November 2004, Neurology) a group of adults with PDS and fluent adults. The PT was measured on volumetric MRI brain scans, and subjects were classified as having a typical leftward PT asymmetry or atypical rightward PT asymmetry.

Prose passages were read at baseline, with non-altered feedback (NAF), and with DAF, and fluency was measured in these three conditions.


In the adults with PDS and atypical PT anatomy,

fluency was improved with DAF.

In contrast, the adults with PDS and typical PT

anatomy did not improve fluency with DAF.

Our results suggest that anomalous PT anatomy

may be a neural risk for developmental

stuttering in some individuals. It may be that

atypical rightward PT anatomy may alter speech

feedback, and treatment with DAF might allow

these people to compensate.

(Anne L. Foundas, 2000&2004


Brain activity during altered auditory

feedback: an fMRI study in persistent and

recovered developmental stuttering

Three groups of healthy adolescents were with

persistent developmental stuttering (PDS); 4

with history of developmental stuttering but

considered recovered on recent testing(RDS)

and 9 fluently-speaking controls.

Functional images were acquired after 7-s

silence which followed a period where subjects

read sentences aloud (96 images in total).

Speech was recorded and fed back to the

subjects via a real-time digitizer


. Feedback was either (i) normal (ii)

delayed by 200ms or (iii) frequency-shifted

by half an octave upwards.

Statistical maps were generated to show

the brain areas active during speaking

under normal feedback across the three

groups.

These areas included the sensorimotor

and premotor cortices bilaterally, the

superior temporal cortex bilaterally, the

supplementary motor cortex, the anterior

cingulate cortex and the cerebellum. KUNNAMPALLIL GEJO JOHN,MASLP

The mean activity in these areas was

calculated for each condition and each

subject separately;

Across all conditions and compared to controls,

the PDS group had 1) significantly less activity in

the sensorimotor and premotor cortices

bilaterally, the supplementary motor area and

the anterior cingulate cortex

2) significantly more activity in the cerebellum;

the RDS group were not significantly different to

the controls or the PDS group.


Frequency shifted Auditory Feedback

FAF downshift makes hear

voice sounding like a gravel-voiced radio

announcer saying his station's call letters.

A quarter-octave pitch shift reduces

stuttering about 35%. A half-octave pitch

shift reduces stuttering about 65-70%. A

full-octave pitch shift reduces stuttering

about 70-75%.

Combining DAF and FAF reduces

stuttering about 80%. KUNNAMPALLIL GEJO JOHN,MASLP

FAF causes non-stutterers to speak at a

higher or lower vocal pitch, depending on

whether the device is set for an up or

down frequency shift.

In other words, FAF induces changes in

vocal fold tension in non-stutterers.

…… induce vocal fold relaxation in

stutterers. Usually, stutterers need a

greater pitch shift, between one-half and

one octave down. Also, the study used

older headphones which lacked the bass

response of today's headphones. KUNNAMPALLIL GEJO JOHN,MASLP

FAF downshifts induce a slower speaking

rate, similar to DAF. If this effect is

consistent, then a FAF downshift should

produce long-term carryover fluency.

Conversely, (the Mickey Mouse voice)

FAF up shifts induce faster speaking rates.

If this effect is consistent, then a FAF up

shift should result in poor long-term

performance (e.g., no carryover fluency,

and possibly "wearing off)


FAF may account for the reduction in stuttering (JSLHR,VOL.42,,1347-1354,1999)

Feedback control theory

Feedback from sensory systems plays a direct role in controlling on going action .

Delaying this feedback results in control errors such as stuttering .

For adults ,repetition errors due to DAF increase as function of delay up to 0.2 msec .Then decrease with larger delays ,but disappears completely even with delays as long as 0.8msec (Mc Kay 1998)


When bilinguals speak under DAF, their peak

delay remains the same (MC Kay

1969)_Bilinguals make more repetition errors

when producing their less familiar language

under DAF, (Mc Kay1970)

Mechanical distortions of the returning

auditory feedback reduce the disruptions

resulting from DAF(HULL1952)


Masking noise ,DAF,frequency shifts and other alterations in the properties of the auditory signal can create temporary fluency in person who stutter( Van Riper1982)

DAF can create an artificial stutter in normal speakers (Black&Lee 1951).

Postma &Klok (1992) ……stutters possess a deficit in their ability to self monitor the accuracy of their speech production and also they may be experiencing prearticulatory errors which they are attempting to covertly repair . KUNNAMPALLIL GEJO JOHN,MASLP

A variety of explanations for the effect of altered feedback ….. it 1)distraction ,2)causes stutterers to change how they talk &3)compensates for a defect in stutterer’s auditory monitoring of their speech (Bloodstein ,1995)

.Stromsta(1957,1972,1986)……. stutterer’s abnormal brain rhythms impair the integration of auditory feedback and speech output .The result is interruptions of phonation & improper coarticulation of sounds .


Stager et al (2003) …….. brain scans during

fluency inducing conditions indicated increased

activity in stutters auditory areas ,reflecting ‘

more effective coupling of auditory & motor

systems ‘ so that auditory feedback could help

to integrate the sequencing of speech motor

outputs


The covert repair hypothesis

This hypotheses makes use of a

monitoring device that checks on the

accuracy of speech .

In this model monitoring takes place

during the formulation of the phonetic plan

and prior to the implementation of

articulatory commands


CONCEPTUALIZER

Preverbal message

FORMULATOR

GRAMMATICAL ENCODING MONITOR

STRING OF LEMMAS

PHONOLOGICAL ENCODING

Phonetic plan

ARTICULATOR efferent auditory feedback

proprioceptive

Tactile feedback

Motor movements sound KUNNAMPALLIL GEJO JOHN,MASLP

Speakers who stutter are impaired in their

ability to encode phonological sequences

,such that the activation of target

phonemes is delayed & placed in

competition with other phonemes

The process of detection and repair in

combination with a system that is not

adept in selecting the correct phonological

target before it is produced results in the

overt manifestation of a speech

dysfluency. KUNNAMPALLIL GEJO JOHN,MASLP

Postma &Klok …… this covert process may

be thought of in much the same way as overt

self –repairing .

This hypotheses nicely explains many of

the dysfluencies of normal speakers and

had been extended to explain the fluency

breaks in stuttering speakers ,for both loci

& type of intrasyllabic dysfluencies .

It supports well with a number of reports of

phonological processing abilities of stutterers

(Bosshardt1990; wingate1988) .


Yarrus & Conture(1996) studied nine boys who

stuttered with normal phonology & nine boys

who stuttered and exhibited disordered

phonology .age range was 5yrs old.

They found that both groups were similar in

their speech dysfluencies , speech errors and

self repair behaviours .Utterances containing

speech errors were significantly more likely to

contain within word speech dysfluencies for

both group of children KUNNAMPALLIL GEJO JOHN,MASLP

Practice & effect of DAF • Practice with a sentence reduces the effect of

DAF because practice strengths internal trace of

the expected feedback &successive movements

are driven by discrepancy between ongoing

feedback &expected feedback or feedback trace

• .This means practice should increase rather

than decrease the probability of errors for

sentences produced under DAF.

•These observations suggest that articulation is

not under the direct feedback

control.(Adams1985).


Reaction time in stutterers

Research has shown that

stutterers as a group are slower in their

reaction times .

These reaction time task s assess

the sensory &motor systems working

together .

Adams& Hayden 1976 found that

stutterers were slower in reacting with

respiration &articulations (lip closing)


• Stutterers are slower in tracking a tone that goes up &down in pitch .Hoyt & Rosenfield 1987

Brain et al 1999&Fox et al 1996 stated that in stutterers there could be decrease in the blood flow in primary auditory areas .


Auditory masking

Shane (1955)&Cherry and Sayer (1956) had reported reductions in stuttering as a result of masking noise during the speech of stutterers .

involved in the use of binaural earphone receiving the output of a low frequency BBN generator .

the noise usually has an intensity level with in 70-100 dBSPL range . As an aversive stimulus it can occur following stuttering spasms & it has been used as a continuous signal to facilitate fluency


.Distraction effect

though distraction cannot explain completely the dysfluency reductions that occur

.some clinicians …….. the vocal signal changes produce as altered motor planning and productions sequence which can explain stuttering reduction through alteration of habituated speech patterns.

Others ……… masking simply reduces auditory feedback and perhaps , requires the speaker to concentrate as proprioceptive signals .

Masking can be used as an in –clinic therapy in order to establish fluency and then be shaped toward normalized speech .


Albert Postma & Herman Kolk(1992) studied on the effects of noise masking and required accuracy on speech Errors , dysfluencies ,and self –repairs(JSHR,VOL35,537-544,1992)

Subjects: 16 women & 16 men aged 19- 32yrs.

Result: with respect to three major issues

(a)The covert repair hypothesis of dysfluency.

(b) the reality of internal monitoring processes,

(c)differences among the various error types in how well they are monitored that is , in the probability that they will be detected and corrected


The covert repair hypothesis of

disfluency (Kolk,1991;Postma et al

1990)explains dysfluencies as by products

of covert self repairs applied to internal

speech errors .

Speakers must pay less attention to the

internal loop,or relax criteria employed in

internal monitoring ,when they could no

longer hear themselves.


A major alternative to this explanation of

reduced dysfluency relates to the

Lombard Reflex.

If delayed repairs reflect the use of

auditory loop for error detection ,naturally

,fewer delayed repairs occur when the

auditory loop is suppressed


Noise masking reduce disfluency and self

repair rates but did not affect speech

error numbers.

Wingate (1970) has claimed these changes in

manner of articulation and phonation to be the

mechanism by which noise ameliorates

fluency in stutterers .


DAF AND STUTTERING

(JSHD,VOL33,260-265,1968)

AIM: In an attempt to explain why stutterers

improve in fluency under DAF

stuttering as perceptual defect

-stutters have disturbed speech auditory feedback loop or auditory perceptual defect (Butler

&stanley1966)

-Stromsta(1956)…… stutterers tend to have larger interear discrepancy than nonstutterers

for bone tissue feedback KUNNAMPALLIL GEJO JOHN,MASLP

Interpretation:

-if external side tone assumed to be similar for

stutterers and nonstutterers, it can be stated that

condition existed with in the stutterers at

2000Hz ,comparable to a delay of their external

side tone ,a phenomenon which has been

demonstrated to disrupt the speech of non

stutteres .

-it was postulated that……. In phase& Out of

phase of a side tone preserved in the cortical

centers and that could cause a central

phenomenon conducive to out of phase of action

potential at paired peripheral muscles during a

stuttering block KUNNAMPALLIL GEJO JOHN,MASLP

The manner in which DAF reduces the

frequency of stuttering can be explained,

1 interpretation; phase differential between

bone tissue and air conducted feedback is

greater near the Fo of stutterers voice .

Soderberg (1959)…. Sts increased vocal

pitch under DAF ,as in the case of

nonstutterers


2 interpretation;

-bone tissue feedback of sts is out of phase

with that of air conducted feedback ,then

DAF restores more suitable phase

relation between these two pathways for

stutterers .

-There is an optimum delay time (Lotzman

1961) that facilitates the fluency of

individual sts , it would seem that specific

delay times play an important role in

correcting auditory feedback . KUNNAMPALLIL GEJO JOHN,MASLP

3 interpretation ;

-the slowing of speech under DAF accounts

for the reduction of stuttering rather than

feedback correction .

It may be necessary for some sts to speak

at slower than normal rate in order to

achieve a degree of stability in their

speech auditory feedback loops .

-Johnson &Rosen(1937) reported that the frequency of stg was greater when sts read faster than normal


TESTS RESULTS OF AUDITORY PROCESSING IN STUTTERING

Auditory threshold

Harms&Malone(1939) ---- 62 stutterers

examined by pure tone audiometry had a

impairment of hearing ,

Tomatis (cited by Van Riper,1982)stated that 90 % of his stutterers had a hearing loss in one

ear .


o Hugo ,Aimard,Plantier & Wittling (1966) could find any difference in sensitivity between the left & right ears of stutterers .

MacCulloch & Eaton (1971) reported a lowered auditory pain threshold for Puretones in a comparison of 44 stuttereres with a group of controls .

Phase disparities

Stromsta (1957) --he used 2 pure tones of equal frequency and amplitude and diametrically (180 degrees ) out of phase .


-Stutterers and normal speakers listened to an air conducted tone and to bone conducted tone of same frequency simultaneously introduced

The subject then varied the phase and amplitude of air conducted tone until a critical adjustment was at which no sound was audible to them .


Stromsta found that at 2000Hz there was

differenc between stutterers and nonstutterers

in the average relative phase angle of air and

bone conducted sounds as indicated by the

amount of adjustment they made


Later by the same method ,Stromsta

found an unusual phase disparity

between stutterers left & right ears .

His subjects adjusted amplitude and

phase of two air conducted tones heard at

either ear until they cancelled an identical

bone conducted tone .


At the point of cancellation the air

conducted tones at the two ears had a

phase disparity at several frequencies

about twice as wide , on the average ,for

the stutterers as for the nonstutterers.

Mangan (1982)replicated Stromasta’s earlier

study and failed to find a difference between

stutterers and nonstutterers in phase and

amplitude adjustments of air and bone

conducted sound .


Test of Central auditory processing

Rouse Y,Goetzinger & Dirks (1959)reported that

stuttering children did not perform as well as non

stutterers in making mediane plane sound location

response.

Sound localization findings by Kamiyama (1964)and Asp (1968),although Asp observed some

differences on tests of loudness balance

Herndon (1967)found differences in the ability to discriminate between different durations of the

tone


the Synthetic sentence identification / Ipsi lateral competing message test (SSI-ICM) to compare stutters &non stutters .

This test requires participants to identify words in a nonsense phrase (such as ―small boat with a picture has become ―) when competing noise is presented in the same ears.

Three studies using this test found that stutters perfomed worse than normal participants (Hall &Jerger ,1978;Molt & Guilford ,1979;Toscher & Rupp,1978)


the more fluent normal speakers performed

significantly better than the less fluent normal

speakers (Wynne&Boehmler

1982&Blood1987).

Stuttering &normal dysfluencies may be

associated with some difficulty in central

auditory processing


o Hannely &Dorman (1982)& Guitar(1987)

found no differences between stutters &non

stutters on the SSI-ICM, but stutters in their

study had all recently completed a treatment

program .

o This finding intriguing in light of evidence

from brain imaging studies … an absence of

activity before treatment in the left auditory

cortex showed normal levels of activity

immediately after treatment (De Neil et al

&Ingham ,2003) KUNNAMPALLIL GEJO JOHN,MASLP

In Staggered spondaic word test ,The

stimuli used are series of 2 bisyllabic

words having equal stress on each

syllable .The syllables are then

overlapped in time The overlapping

syllables a dichotic input to the listener

.Hall & Jerger(1962)stated that stutterers

&nonstutterers significantly differed in their

total correct responses to the competing portion

of the test .Stutterers performed poorly on this

test when compared to non stutteres KUNNAMPALLIL GEJO JOHN,MASLP

masking level difference test (MLD) ,which requires listener’s to detect the onset &offset of a tone in the presence of masking noise . When masking noise is played in the same ear as the tone ,there are fewer cues for listener’s to use in filtering the tone from the masking tone

Listener’s must use very subtle temporal cues to detect the tone ; under these conditions ,persons who stutter perform more poorly than groups of nonstutters(Guitar 1987) .


These results may be interpreted to support the

outcome of the SSI studies because both tests

require the participants to use temporal

information –in one case (SSI), rapidly changing

formant frequencies in identifying words , and in

the other case (MLD),detection of the onset

&offset of a tone in masking .

central auditory processing tested the

hypothesis that people who stutter have

difficulty resolving temporal differences

.Herndon (1966) found that stutters were

poorer than nonstutters at distinguishing

Which of two brief tones was longer KUNNAMPALLIL GEJO JOHN,MASLP

Barasch et al (2000) administered the duration

pattern sequence (DPS) test ,which involves

judging the relative lengths of three tones ,

and another measure in which subjects

estimated durations of tones & silent intervals These tests failed to distinguish between the

stuttering &nonstuttering participants as groups

,but they showed that less –fluent participants

in each group scored worse on the DPS than

more fluent participants .

In addition ,more disfluent subjects in both

groups judged temporal intervals to be longer

than less disfluent subjects KUNNAMPALLIL GEJO JOHN,MASLP

It has been suggested that fear &anxiety affect temporal processing (Fraisse 1963)

that anomalies in temporal processing may be an underlying cause of both stuttering (Kent 1984 ) and high levels of normal disfluency(Wynne1982)

Researchers conclude that stutterers performance is poor on all these central auditory function tests .Stutterers as a group performed poorly than nonstutters on task requiring fine discrimination of the small time difference in signals .


Researches view stuttering as disorder in

the control of sequence & timing

.There are 5 observations which point the

connection between stuttering

&processing of auditory input

1)Stuttering can be virtually eliminated in

some with the flick of switch introducing

white noise with in the frequency range of

speech which is loud enough to mask the

stutterers auditory feedback (1955)


2)Stapedial reflex of the middle ear

appears to differ between stutteres &

nonstutterers ..The stapedial muscle

normally contracts 100-165 msec prior to

phonation ,there by reducing the amplitude

of the ear drum vibration & alternates the

hearing of ones own speech .

Webster &Lukes(`1968)found that stapedial

reflex is less stable in stutterers


Dhonovitz & Johnson et al (1978) found that under conditions of anxiety stutteres show less stapedial attenuation than nonstutters .

Hall & Jerger (1978) compared the acoustic reflexes in stutterers &controls . Reflex threshold was equivalent was in 2groups ,but reflex amplitude was smaller in stuttering group

Hannley and Dorman (1982) observed nodifference in the latency or amplitude of the reflex.

March banks &El-Yaniv(1986) found nodifference between stutterers and normal speakers in middle ear muscle activity during vocalization . KUNNAMPALLIL GEJO JOHN,MASLP

3)Auditory processing of an about to be produced word facilitates its correct production

Stutterers often release them from a block when someone else word on which they have difficulty (Bar &Carmel 1970)

4)stutterers become very fluent when their returning auditory feedback is delayed by means of a recording &reproducing device (Hutchinson& Burk1973)


5)Reception errors like in stutterers can be obtained in normals by amplifying as well as delaying their auditory feedback

Researchers have tried to link the timing deficit to stuttering by suggesting a single mechanism in brain may control both incoming and outgoing signals

Faulty timing of incoming signals would give rise to stutterers poor performance on central auditory processing tests .Faulty timing of outgoing signals would result in stuttering


Dichotic listening tests

In the early studies ,a procedure

was developed to assess hemispheric

dominance for speech &language by

testing which ear was more accurate at

hearing speech sounds

.Kimura 1961 invented the dichotic listening test

, which simultaneously presented two

different syllables dichotically .


Listeners reported which syllable they

heard .auditory nerves connecting the ears

to the cerebral hemisphere carry more

information to the hemisphere on the

opposite side than to the hemisphere on

the same side .

Results with normal speakers indicated

that syllables presented to the R ear were

most frequently reported as heard ,which

was called a R ear advantage for speech .


This procedure has been used to assess

laterality differences between stuttering

&nonstuttering groups .A number of

experiments found that many persons

who stutter do not show the typical R ear

advantage that nonstutters do ,which is

evidence that people who stutter

some dichotic studies found no difference

between stutters &nonstutters (Dorman

1975&Pinksy &McAdams ,1980)


Other studies found no significant group

differences but found that fewer stutteres than

nonstutters showed the expected Rear

advantage (Rosenfield &Goodglass 1980) .The

more linguistically complex the stimulus ,the

more likely that the differences between stutters

&nonstutters would be found .

Any auditory processing anomaly

related to stuttering is likely to be on a

continuum rather than simply present or absent

.More severe or neurologically involved stutters

may have more abnormal auditory processing


Left-handed men who stutter and right-

handed women who stutter have atypical

auditory processing but differ in important

ways. The left-ear bias found in left-

handed men who stutter in the nondirected

attention condition suggests that their right

temporal lobe may be important in

perceiving speech, and, therefore, they

have mixed dominance

(Cogn Behav Neurol2004 Dec;17(4):224-32)


Lombard sign

Panconcelli-Calzia (1955) found the lombard

sign in only 27%of a group of 80 stutterers ,as

compared with 78% of a group with normal

voice and speech .This is a conflict with

considerable amount of research showing that

most stutterers do increase the loudness of their

voices under masking noise.


Brain electrical potentials reflecting auditory processing

Studies of electrical brain activity in response to auditory stimuli have provided further evidence that auditory processing is abnormal in individuals who stutter .

Molt and Luper(1983) found that stutterers had faster average peak latency than normal speakers


Studies by Hood(1987)&Parker (1995)

reflecting both subcortical &cortical activity

have found group differences between stutters

&nonstutters . However the study found

stutters responses to be slower than

nonstutters responses .


A study of Molt(1997) brain imaging studies of whether person who stutter have a deficit in the left auditory cortex Molt found that stutters have longer latencies &lower amplitudes of brain waves in the cortex when they where asked to make decisions about semantic incongruencies in sentences they listened to


Early latency potential (ABR)

Blood &Blood (1984) recorder longer wave III and wave V latencies for stutterers and abnormal inter peak latency for five of eight stutterers .

Smith,Blood and blood (1990) found no differences in latencies but greater amplitude of wave I for stutterers .


Middle latency response in stutterers

Studies have shown that auditory middle latency response Wave Pb was prolonged in subjects who stutter as compared to normals

.

Hood (1987)conducted an investigation of the MLR s of of males who stutter and found that the latency of the wave Pb was significantly longer for those who stuttered than controls .MLRs were recorded from 10 males who stutter &10 controls using a variety of filter bands in response to clicks presented binaurally at various rates .


The latency of Pb was found to be significantly

shorter in the group of subjects who stutter.

Wave Pb of the MLR is generated by the

thalamic portion of the reticular activating

system .The thalamus is critical to speech and

language production .Other researchers suggest

that the metabolism of the thalamus is lower

than normal(Rapoport1991)(JSHR,Vol.38,5-

17,1995);


Significant difference in the delay of Wave Pb

latencies in adult stutters as compare to the

adult non stutters in both ears .This indicate the

differences in the thalamocortical pathways

&reticular formation as there are hypothesized

to be the possible generators for the MLR

waves .The difference may lead to poor

temporal processing &programming in stutterers

. Msc Dissertation of Osmania

University 1997)


P300 event related potentials in stutterers

Stutters exhibit different patterns of interhemispheric activity than nonstutters with a tonal P300 task.

Insula and auditory cortical areas of the superior temporal lobe are majorities of generation of the P300 response (Rogers et al 1991)Ferrand,Gilbert and Blood (1991) tested stutterers using P300 and found nodifferences between stutterers and nonstutterers in the latency of p300.16 young adult males aged 17 to 36 years with R handed compared with stutterers and found that stutterers exhibited relatively lower amplitude P300s in the right hemisphere


This may be interpreted as possibility that

altered cerebral dominance plays an

important role .(Mattingly

1970)(JSLHR,Vol40,1334-1340,1997)


Effect of auditory feedback on Non speech Oral activity Both stutterers and nonstutterers the

delayed feedback conditions produced disturbances in the pattern such as errors ,prolonged lip closures , and prolongation of the pattern .However the effect of DAF was about the same for both group of subjects .


Effect of DAF in normal speakers

It is possible by means of magnetic tape

recording &recording device suitably

designed to return a subjects vocal output

via earphones with a brief delay in

transmission

2explanations are given about the effects

of DAF in normal subjects


normal speakers air conducted auditory feedback is by the interval of the order 0.2sec& amplified sufficiently to complete with their bone conduction feedback ,there tends to be a disintegrative effect on their verbal output

.this disintegration takes the form of a slow speaking rate ,articulatory inaccuracy ,disturbances of fluency including blocks &repetitions of the syllables like in stutters . In addition there is an increase in loudness & pitch ,which Fairbanks inferred to result from the subjects struggle to resist the interference with their response


Following activation ,the nodes responsible for speech are self inhibited & then undergo a normal cycle of recovery .

this recovery cycle includes a period of hyper excitability during which nodes have greater than normal sensitivity, with a peak occurring approximately 200msec following onset of activation & return to a resting level by 300msec following onset of activation

.this explains why the delay of 0.2 sec produces maximum disruption of speech


.When feedback arrives 0.2sec after onset

of activations ,it provides additional

priming of just activated nodes ,

(amplification ,hyper excitability & normal

bottom up priming )combine to exceed the

top down priming of appropriate nodes

,these just activated nodes will be

reactivated under most primed principle

,with an effect resembling the repetition

errors of stutterers


Errors under DAF decrease with slower speech

rates ,since lower speech rates enables

temporal summation to augment top down

priming of nodes for an indented output .

This may explain why some subjects speak

slower at the most disruptive feedback delay

(0.2sec )despite instruction to speak always at

a maximum rate .By speaking slower they can

overcome the effects of returning auditory

feedback &gain better control over the output .


Effect of DAF on stutterers

Under the theory stuttering occurs whenever the just activated nodes receive greater priming than nodes to be activated next .There are 2 hypothesis to account for this theory.

One hypothesis is that returning feedback is delayed by about 0.2 sec with in the sensory analysis nodes of stutterers & acquires greater than normal amplitude due to mal functioning of the stapedial reflex .As a result the normal auditory feedback of these stutterers will achieve the conditions ,which disrupt the speech of normal speakers receiving delayed & amplified auditory feedback

.Like wise shadowing & choral rehearsal prevents stuttering by augmenting the priming of the appropriate or next to be activated nodes


The other hypothesis is that nodes of stutterers, evidence an abnormal recovery cycle .

Both hypotheses predict that masking & returning auditory feedback will reduce the probability of stuttering &amplifying it will have the opposite effect .Both hypotheses predict release from auditory input guides speech production Thus stuttering is overcome when others utter the words when stutter is blocking since the input helps prime the appropriate nodes to the level required for activation . Finally both hypotheses predict that delay producing maximal interference with speech will be shorter stutters than non stutterers .


Brandt & Wilde (1977)found that like

stuttering ,the dysfluencies of normal speakers

under DAF was reduced when the subject

read in unison with another voice & they

timed their speech to the beat of a metronome .

Borden et al (1977) observed both similarities

&differences between normal speakers under

DAF &stutterers in electromyographic

recordings from laryngeal & articulatory

muscles


Venkatagiri(1982) found that like stutterers

the DAF dysfluencies of normal speakers

showed a distinct adaptation , effect over

successive recordings occurred more

often in content words than on

functional words , on long words than on

short words . Although the consistency

effect was present,it was smaller when

compared to stutters .


Studies

Studies have shown that DAF at short delays

&frequency altered feedbak have been shown

to produce immediate &extremely powerful

reduction of stuttering(FoliaPhoniatrica et

Logopedica2004,56,347-357)

Vowel duration significantly increased

under metronome,DAF, and noise ;pressure rise

time increased under MET ,DAF &noise;flow

rise time increased under noise;speech rate

decreased under DAF & noise

(JSHR,vol36,245-253,1993)


Noise masking reduced disfluency and self repair rates but did not affect speech error numberers(JSHR,VOL 35,537-5444,1992)

Significant decrease in number of stuttering blocks under binaural masking noise condition in case of stutterers .Normals showed no stuttering blocks under binaural masking .an increased vowel duration found in both groups

(JAIISH,VOL.XIII,1982),Msc dissertation; Nadur V.U(1982).


The error detection performance of subjects who stuttered was compared to that of subject who didn’t in two speech production conditions ;one with normal auditory perception &one in which the auditory perception was masked by white noise ;and in perception condition in which they are listened to speech produced by another person

.In both the normal speech &noise masked conditions that the error detection rates &false alarm rates of subjects who stuttered did not differ significantly from those of subjects who did not stutter(JSHR,VOL35,1024-1032,1992)


stuttering and auditory functions .pdf / kunnampallil gejo

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