Stuttering and auditory functions..pdf/ KUNNAMPALLIL GEJO

7/27/2019 Stuttering and auditory functions..pdf/ KUNNAMPALLIL GEJO

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Stuttering and auditory

functions.

KUNNAMPALLIL GEJOJOHN,MASLP



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Content :

(1) Introduction.

(2) Auditory processing.

(3) Dichotic listening.

(4) Phase disparity.

(5) Acoustic reflex.

(6) Theoretical explanation of the auditory

effects.

(7) Types, tools, applications & effect of

auditory feedback.

(8) Tests results of auditory processing in

stuttering.



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INTRODUCTION :

Perkins, 1990

Stuttering is the involuntary disruption of a

continuing attempt to produce a spoken utterance.



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Auditory processing :

Term used to describe the recognition & interpretation of a

sound by the brain.

Ear acoustic to electrical interpreted by brain.

Learning to speak involves motor process.

sensory process.

Self hearing helps to -- monitor ones own speech.KUNNAMPALLIL GEJO

JOHN,MASLP


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Aspects

ofauditory functions

Relative phase

angle of air &

bone conductedsounds

Threshold for

pure tones

Effect of aud

fn on oral

activity notinvolving sp.

Central aud fng

at level of

brainstem.

Dichotic

listening.

Reflex

response of

ME msls to

sd.



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Auditory processing in stutters :

Stuttering may be the result of errors of stutterers self hearing

aspect.

In exploring this hypothesis , researchers have measured how

stutterers CNS process different sounds including speech.

The resulting hypothesis was that stuttering may have its origin

because of malfunctioning of the hearing mechanism in its role as

rural monitor.



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Findings of all aspects of physiological functioning in

stutterers :

(1) central auditory function in stutterers

Hall and Jerger assessed auditory function in 10 stutterers and 10

non-stutterers.

Performance for the 2 groups was compared for 7 audiometric

procedures including -- auditory reflex threshold, acoustic reflex

amplitude function, performance intensity, function for

monosyllabic phonetically balanced (PB word) performance

intensity for SSI, SSI-ICM, SSI-CCM and SSW.



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Acoustic reflex amplitude function, synthetic identification with

ICM and SSW test

As a group stutterers presented evidence of a central auditory

deficiency.

The pattern of the test result suggested in brainstem level.

The subjectivity of the deficiency is emphasized.

In 1959, Rousey, Goetzinger and Dirks observed that stutteringchildren perform less well than non stutterers in localizing sounds

in space.



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(2) Central processing in stuttering :

Hemispheric properties of stuttering --

Brain waves of stutterers have been examined & compared those

with non stutterers.

Manifestations of cortical dominance were studied .CNS

investigation suggested that stutters lack cerebral dominance for

speech.

Lindshy &Freestone (1942) suggested that stutters demonstrateright hemisphere dominance for language.

Wilkins EEG studies shown that final neural dysfunction rather

than hemispheric differences in stutterers.KUNNAMPALLIL GEJOJOHN,MASLP


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Right hemisphere activity --

Difficulty in

- Central auditory processing,

- Language development,

- Speech motor reaction time &

- Delay in tracing auditory stimuli

(may all be related to organization of speech, language & auditory

functions in brain).

People with stuttering may be using less effective part of brain for

processing speech functions.



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Fox (1996,2000) - decreased activity in auditory area during

increased stuttering ,so reduces the left brain communication of this

sensory information to frontal speech & language areas.

The abnormal right brain activity may be alternative pathology for

brain sensory information to travel to the front of the brain .

People who stutter use Right hemisphere which leads to

intermittent break down ,because Right hemisphere is not as adopt

as the left for processing rapid transmission that characterizesspoken language.

Right hemisphere is also associated with emotional expression.



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This suggestion has implication for the onset of stuttering in

childhood when many functions appear to have bilateral

representations.

Fluency may be vulnerable to emotional disturbances & caused by

excessive amounts of neurotransmitter dopamine in the left caudate

nucleus. (This is the area that translates speech into muscle

movements).

There is no conscious awareness of central auditory processing in

left caudate nucleus (This explains why stuttering that relay in

consciously controlling speech best only temporarily).

Inability to integrate what stutterers hear with the muscle

movements that he feels.



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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 auditoryassociation areas & Wernickes area (FOX et al ,2000&DE NIL

et al,2003).

These findings suggest the possibility that when individual

stutter they are not using auditory feedback to monitor & control

their speech.

Another imaging study (SALMELIN et al ,1998) found that

stutters have a reversal of the normal pattern of activation ofthe left & right auditory cortices during stuttering .



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Stutters may have difficulty performing auditory processing tasks

(BARASCH et al ,2000) and that fluency can be induced by

changing the way stutters hear their own speech (BRAYTON &CONTURE ,1978;POWELL ,1987).

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 executes the utterance.

Thus the dyssynchrony or timing disturbance are the basis of

stuttering (Perkins,Kent,&Curlee,1991;Van Riper 1982) may becaused by a paucity of signals that synchronize the sequence for

speech output.



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Therapies that focus on the use of slow speech, gentle onset, and

light articulatory contacts may develop the clients auditory as well

as proprioceptive monitoring of speech.

Craver & Faber1982, Moore1986 found that stutterers have poor

recognition & recall of words on auditory presentations.

Carpenter & Sommers1987 found stutterers & nonstutterers have

equal auditory memory.

Dichotic listening :

In the dichotic listening paradigm, different sound are presented

simultaneously to the two ears.



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The listener must report everything he hears from both ears.

Since the sounds are simultaneous it is presumed that the listenermust alternate attention between the two ears, placing one percept

in short term memory while attending to the other and vise versa.

When normal adults are tested in the dichotic paradigm, there is a

slight advantage for certain sounds delivered to the right ear and for

other sounds delivers to the left ears.

Kimura was the first to demonstrate that verbal signals such as

words and digits are more accurately reported from the right ear (ie,left hemisphere) than from the left ear (ie, right hemisphere).



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After simultaneous dichotic presentation (Kimura, 1961,1967) the

reverse is true for melodies (Kimura 1967).

If stutterers are, indeed, lacking in suitable hemispheric dominance

for language, this fact should be readily revealed by a dichotic test.

Variables in dichotic testing. :

(1) It is important, for example, to ascertain the handedness of the

subjects being tested stating that subjects are right or left handed is

not as meaningful from laterality standpoint as the administration

of a detailed handedness questionnaire (Oldfield, 1971).



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(2) Another variable is the order in which subjects are instructed to

report sounds (ie, right ear first, left ear first, or either ear first).

Most investigators who have controlled this variable have notedthat there is a greater index of cerebral laterality when subjects

are instructed to report first from left ear and then from the right

ear.

(3) Another variables is the stability of the dichotic ear advantage

over time. Blumstein, Good glass and Tarter (1975), employing a

test retest experiment, contend that 85% of normal right handed

males have a right ear advantage in dichotic listening and that

any such test sample contains 15% misclassified subjects.

They observed that as many as 30% change ear dominance

when retested. Thus consistency between test and retest is an

important dimension in studies of cerebral laterality.



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Dichotic listening paradigms test a response to a sound input. The

test evaluates cerebral laterality in a steady state, it does not

evaluate laterality in the dynamic state of speech production.

This may be very important in the investigation of stuttering.

Suppose, for example that stutterers have a disturbance in cerebral

laterality that causes a compromise in their speech output.

This abnormality may not be static, that is, it may only appear

during speech or perhaps only at certain times during speech

production.



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Dichotic listening in stutterers :

Curry and Geogory (1969) used a dichotic listening paradigm with20 adult stutterers (19 males, 1 female) and 20 appropriate controls.

All were stated to be right handed.

The author employed several dichotic tasks, one of which was the

dichotic word test.

The test involves the recognition of pairs of consonant vowel

consonant (CVC) words of high familiarity presented in groups of 6

pairs with 0.5 sec separating each pair.

After each group of 6 word pairs had been presented, the subjects

attempted to recall the 12 different words, in any order and without

concern for which words had been presented to any particular ear.KUNNAMPALLIL GEJOJOHN,MASLP


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The anticipated right ear superiority was significantly less for

stutterers than for non stutterers.

75% of the non stutterers had right ear scores that were higher than

their left, this was true for only 45% of the stutterers.

Dorman and Porter (1975) evaluated 16 right handed adultstuttereres (12 males, 4 females) and compared them to 20 controls

(10 males, 10 females) subjects had to write down responses to

synthetically generated consonant vowel dichotic stimuli.

There was no significant difference between stutterers and non

stutterers.



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Pinsky and Mc Adam (1980) tested 5 adult stutterers and 5 fluent

speakers in a dichotic listening paradigm. All individuals were right

handed except one who was stated to be weakly right handed. Theauthors failed to find a significant difference between the stutterers

and non stutterers.

Rosenfield and Goodglass (1980) queried whether the above study

had failed to take into account a number of variables that might

affect the results. Children stutterers, for example, might be

different from adult stutterers.

In an effort to control all relevant variables. Rosenfield andGoodglass (1980) evaluated a group of adult male, strongly right

handed, stuttereres.



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They evaluated left cerebral dominance for language using

consonant vowel stimuli and tested right hemisphere laterality for

melodies by testing melody input.

Right ear advantages were obtained for consonant vowel stimuli

and left ear advantages were noted for melodies output significant

disturbance between the groups of stutterers and controls.

However, there were significantly greater number of stutterers than

controls who consistently failed to show the expected ear laterality

for either type of material.

As pointed out by Moore (1976) stutterers seem to differ fromnonstutterers when investigators employ meaningful verbal stimuli.

Of the dichotic studies that employs words or digits, rather than

meaningless consonant vowel or other stimuli, most find difference

between stutterers and non stutterers.KUNNAMPALLIL GEJOJOHN,MASLP


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Sussman and Mac Neilage (1975) employed a dichotic paradigm

and other paradigm, that of pursuit auditory traking.

They reasoned that dichotic listening tested elements of laterality

pertaining to speech perception, where as the tracking paradigm

test speech production.

Their experiment involved matching the frequency of the variable

tone in one ear to the to the frequency of the externally varied tone

in the other ear.

The former tone was altered by a transducer attached to the tongue

or jaw. KUNNAMPALLIL GEJOJOHN,MASLP


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The subject varied the frequency of this tone by approximately

moving tone or the jaw, subjects were required to match the

frequency of this transducer related tone to the frequency of theexternally varied tone.

The authors tested the right handed male and female stutterers andnonstutterers for laterality pertaining to speech perception (dichotic

listening) and speech production (tracking paradigm).

They noted a right ear advantage for both nonstutterers andstutterers on the dichotic studies, stutterers did not differ from

nonstutterers in laterality on the speech perception task.



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On the tracking paradigm, however normals had right ear advantage

whereas stutterers did not (i.e. nonstutterers best altered the

transducers tone when they heard it in the right ear and had to matchit against the externally varied tone in the left as opposed to having

a transducer tone in the left and the extremely varied tone in the

right).

This indicated left hemisphere dominance for nonverbal output.

Stutterers failed to demonstrate such laterality for non verbal output.



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Phase disparity :

In order to study intrinsic abnormality in the stutterers auditorymonitoring system, phase disparity between air and bone conducted

tones was studied.

In 1957, stromosta exploited the fact that two pure tones. 180degree out of phase but equal infrequency and amplitude, will

cancel each other out.

Stutterers and normal speakers listened to an air conducted tone

introduced to the ear and to a bone conducted tone of the samefrequency simultaneously introduced at the teeth.



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Subjects were asked to vary the phase and amplitude of air

conducted tone until a critical adjusted was achieved at which no

sound was audible to them.

There was a significant difference between stutterers and

nonstutterers in the relative phase angle of the air and bone

conducted sounds at 2000 Hz.

Using a similar method, Stromsta (1972) noted an unusual phase

disparity between stutterers left and right ears.



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The acoustic reflex :

One component of the total auditory monitoring system, theacoustic reflex has come under particular scrutiny because of its

intimate relation to vocalization.

The stapedius muscle contracts during vocalization, Brog andZakrisson (1975) visually and electromyographically evaluated

stapedius muscle activity that accompanied vocalization in fluent

speaker who had a perforated tympanic membrane.

EMG activity in the stapedius muscle accompanied speech, even atlow levels of phonation.



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Stapedius EMG activity occurred before the onset of vocalization

in 55% of their cases and after vocalization in 45 % (Borg and

Zakrisson, 1975) in the former instance the time difference betweenreflex onset and phonation onset was less than 75 msec.

The authors concluded that EMG activity in the spapedius muscleis not caused by feedback of the voice signal but, rather is centrally

mediated as a component of the vocalization process.



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Shearer and Simmons (1965) investigated stapedius muscle activity

in stutterers and non stutterers in ongoing speech.

They observed that stapedius muscle activity tended to parallel

vocalization in non stutterers.

In stutterers, however, parallelism was less consistent.

At time, the onset of stapedius activity seemed to be delayed

relative to the onset to the vocalization.

Hall and Jerger (1978) compared the acoustic reflex to external

sound in stutterers and controls. Reflex threshold was equivalent in

the two groups but reflex amplitude was smaller in the stuttering

group. KUNNAMPALLIL GEJOJOHN,MASLP


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Theoretical explanation of the auditory effects :

Feedback control theory has provided the main framework forexplaining the relation between stuttering and the processing of

auditory feedback.

Under feedback control theory,

(1)Feedback from sensory system plays a direct role in controlling

ongoing speech action.

(2)Delaying feedback results in speech control errors such asstuttering.

(3)Feedback control theory has never achieved a detailed

explanation of instances of stuttering (Garber and Seigel, 1982).KUNNAMPALLIL GEJOJOHN,MASLP


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Evidence supported by theory :

(1) Errors under DAF decrease with slower rates of speech sinceslower rates enable temporal summation to augment top down

priming of nodes for an intended output.

(2) Some subjects speak slower/ louder at the most disruptivefeedback delay despite instructions to speak always at maximum

rate. By speaking slower/ louder they can overcome the effects

of the returning feedback and gain better control over the output.



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Auditory feedback :

As we talk, the information is feedback to the brain by the way ofnumerous circuits.

These are called closed circuits or cycles ,which have all

components completely contained within speakers mechanism .

They provide the information to the speakers about what he said &

how he said it by the way of auditory, tactile & kinesthetic modes.

The return flow of information provided by these circuits helps tomonitor our own speech.

Errors are normally identified & corrected automatically .This

process is important for all learning behavioursKUNNAMPALLIL GEJOJOHN,MASLP


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Closed loop system

System organizes in closely connected special & temporal units.

There will not be any time normal course for the speaker topause & check the adequacy of the utterance after each word,

phrase or even after sentence uttered.

Hence, speech once learned become self regulatory withsatisfactory monitoring depends up on the proper functioning &

integration of the of the all feedback circuits .



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Types of auditory feedback :

(1) 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 voice in headphones distorted.

Hearing a synthesized sound in headphones mimicking

phonation (masking auditory feedback, or MAF).

Hearing voice in headphones delayed a fraction of a second(delayed auditory feedback, or DAF).



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These phenomena are called altered auditory feedback.

No brain scans have looked at stutterers' auditory processing while

speaking with altered auditory feedback.

Hypothetically, introducing errors targeted at the area that integrates

auditory and somatic processing increases blood flow to that area,

increasing activity level to normal.

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.

Too much activity is as bad as not enough activity.



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Interestingly, the effects of too much activity in this area are

somewhat like stutteringrepeating 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.

The proportion of stuttering events prescribed telephone

conversations were significantly reduced in the AAF conditions

relative to the non-altered auditory feedback condition.



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(2) Delayed auditory feedback --

It refers to a delay in the return of the air conducted speech signalto the central auditory system.

As an electronic or mechanical phenomenon ,it was reported by

LEE(1950)who coined the term artificial stutter and commend onits fluency disruption effects.

The most disruptive interval was found to be in the 180-200 msec

(Fairbanks & Guttman 1958:Ham &Steer1967).



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The basic observation with which we are concerned is that when

normal speakers air conducted auditory feedback is retarded by a

time interval of the order of 0.2secs. amplified sufficiently tocomplete with their normal bone conducted feedback ,there tends

to be a disintegrative effect on their verbal output .

Delayed auditory feedback (DAF) apparently degrades the

individuals ability to self-monitor his or her ongoing speech.

In the normal speaker, the introduction of DAF via headphonesbreaks down the speakers fluency, often producing prolongation

of vowels and slurring of articulation.



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Under conditions of DAF, most normal speakers will show 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 stutterers rate of speech is often facilitative for

improving overall speech fluency.



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Procedures for DAF :

1. The selector mode on the Facilitator is set to DAF (the lettersDAF 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 (timing changes in msecs

are achieved by adjusting the delay time to the value appearing in

the instrument window).



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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 wont be ableto hear yourself as you usually do when you speak. Just keep

speaking. I will record on another recorder how you sound.

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 isrecommended 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.



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Tools used in auditory feedback --

Metronomic Pacing.

Delayed Auditory Feedback (DAF).

Looping.

Time-Warping.

Masking.

KUNNAMPALLIL GEJO

JOHN,MASLP


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(1) Pacer

The pacer provides metronomic pacing in the form of an

audible click to help assist patients with the timing/rhythm aspectsof speech production.

Among these are stutterers and patients with motor speech

disorders such as cerebellar ataxia and Parkinsons disease.

The pacer rate is adjustable from 50 to 150 beats per minute

adjustable in 5 beat increments.

(2)Delayed Auditory Feedback

The AFT program provides DAF, as a form of disruptivefeedback, which has proven to be effective in fluency therapy.

The DAF in AFT has a range of feedback from 150-500

milliseconds, adjustable in 10-millisecond increments.KUNNAMPALLIL GEJO

JOHN,MASLP


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(3)Looping Playback

Looping records the patients (or clinicians) speech and then playsthe digitally recorded speech back immediately.

This is 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 incrementsKUNNAMPALLIL GEJOJOHN,MASLP


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(4)Time-Warping

Time-warping provides the ability to record a patients speech

and immediately play the speech back at different rates withoutchanging 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.

(5)Masking

In masking mode, 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 enhancethe proprioception of speech/voice behaviors (e.g., easy onset,

eliminating hard glottal attack, etc.).

KUNNAMPALLIL GEJO

JOHN,MASLP


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Applications of DAF :

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.

KUNNAMPALLIL GEJO

JOHN,MASLP


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(1) Planum Temporale Abnormality and DAF --

The planum temporale (PT) is an anatomical feature in the auditorytemporal brain region.

Typically people have a larger PT on the left side of their brains,

and smaller PT on the right side (leftward asymmetry).

A brain scan study found that stutterers have the opposite: their right

PT is larger than their left PT (rightward asymmetry).

A second study found that stutterers with this abnormal rightwardasymmetry had significantly improved fluency with DAF, but

stutterers with the normal leftward asymmetry didn't improve with

DAF.

KUNNAMPALLIL GEJO

JOHN,MASLP


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The study also found that stutterers with this abnormal rightward

asymmetry 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.)

(2) Delayed Auditory Feedback Most Helpful for Those Who

Stutter with Atypical Auditory Anatomy --

(American Academy of Neurology-)

Researchers in New Orleans have identified a subset of stutterers

that may benefit most from delayed auditory feedback (a technique

by which the original acoustic speech signal is artificially modified

and then fed back via headphones).KUNNAMPALLIL GEJO

JOHN,MASLP


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Findings of their study were Delayed auditory feedback (DAF) has

been shown to induce fluency in many individuals who stutter,

though not all stutterers experience enhanced fluency by thistechnique.

The primary aim of this 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.

The planum temporale is a brain structure important in processing

auditory information.

KUNNAMPALLIL GEJO

JOHN,MASLP


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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 disfluent at baseline and had fluency

induced with DAF," (Anne Foundas, MD,)

"However, deficits in auditory processing cannot account forstuttering 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."KUNNAMPALLIL GEJO

JOHN,MASLP


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Effect of auditory feedback on Non speech Oral activity :

Both stutterers and nonstutterers the delayed feedback conditionsproduced 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.

It was only under DAF that any difference appearedstutterers

tend to have longer lip closures.

KUNNAMPALLIL GEJO

JOHN,MASLP


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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.

KUNNAMPALLIL GEJO

JOHN,MASLP


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Two explanations are given about the effects of DAF in normal

subjects :

(1) 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 responseKUNNAMPALLIL GEJO

JOHN,MASLP


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(2) 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 providesadditional priming of just activated nodes ,that produced it at

precise times

KUNNAMPALLIL GEJO

JOHN,MASLP


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When three sources of additional priming (amplification, hyper

excitability & normal bottom up priming) combine to exceed the top

down priming of appropriate nodes, these just activated nodes willbe 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 downpriming of nodes for an intented 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.

KUNNAMPALLIL GEJO

JOHN,MASLP


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Effect of DAF on stutterers :

Under the theory stuttering occurs whenever the just activatednodes 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 & aquires

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 .KUNNAMPALLIL GEJO

JOHN,MASLP


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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 guidesspeech production.

KUNNAMPALLIL GEJO

JOHN,MASLP


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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 .KUNNAMPALLIL GEJO

JOHN,MASLP


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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 .

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JOHN,MASLP


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Practice & effect of DAF :

Practice with a sentence reduces the effect of DAF becausepractice 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).

Many more explanations are need to understand the relation

between stuttering &processing of auditory input.KUNNAMPALLIL GEJO

JOHN,MASLP


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(3) Frequency shifted Auditory Feedback (FAF) :

FAF downshift makes hear voice sounding like a gravel-voicedradio 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%.

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JOHN,MASLP


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Shifting pitch up or down is equally effective in short-term studies.

But there may be long-term differences between up- anddownshifts.

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.

This higher or lower pitch vocal pitch results from changing vocal

fold tension.

In other words, FAF induces changes in vocal fold tension in non-

stutterers.

Speech clinics have reported that FAF devices induce vocal fold

relaxation in stutterers.KUNNAMPALLIL GEJO

JOHN,MASLP


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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.

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, a FAF up shift (the Mickey Mouse voice) appears toinduce vocal fold tension. 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

"wearin off .KUNNAMPALLIL GEJO

JOHN,MASLP


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Tests results of auditory processing in stuttering :

(1) Auditory threshold :

Early report by Harms& Malone(1939)that each of 62 stutterers

examined by pure tone audiometry had a impairment of hearing,

but a succession of further studies failed to disclose any significant

lose.

Tomatis (cited by Van Riper,1982)stated that 90 % of his stutterers

had a hearing loss in one ear and related it to a theory involving

both auditory feedback and cerebral dominance.

Hugo,Aimard,Plantier & Wittling (1966) could find any difference

in sensitivity between the left & right ears of stutterers.

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JOHN,MASLP


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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) in his study he used 2 pure tones of equal

frequency and amplitude and diametrically (180 degrees ) out ofphase cancel each other out.

Stutterers and normal speaker listened to an air conducted tone

and to bone conducted tone of same frequency simultaneouslyintroduced.

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 .KUNNAMPALLIL GEJO

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Using this procedure at frequencies of 500,1000,2000Hz,Stromsta

found that at 2000Hz there was differenc between stutterers and

nonstutterers in the average relative phase angle of air and boneconducted sounds as indicated by the amount of adjustment they

made.

Later by the same method, Stromsta found an unusual phasedisparity between stutterers left & right ears.

His subjects adjusted amplitude and phase of two air conductedtones heard at either ear until they cancelled an identical bone

conducted tone.

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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 Stromastas earlier study and failed to

find a difference between stutterers and nonstutterers in phase

and amplitude adjustments of air and bone conducted sound .

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JOHN,MASLP


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(2) Central auditory processing test :

Research has assessed how well individuals who stutter can processauditory signals in various parts of the brain.

Rouse ygoetzinger & 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)

were in agreement with those of Gregory ,although Asp observed

some differences on tests of loudness balance and Herndon(1967)found differences in the ability to discriminate between

different durations of the tone .

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JOHN,MASLP


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A number of studies used 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 performed worse

than normal participants (Hall &Jerger ,1978;Molt & Guilford,1979;Toscher & Rupp,1978).

KUNNAMPALLIL GEJO

JOHN,MASLP


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The more fluent normal speakers performed significantly better

than the less fluent normal speakers (Blood et al,1987).

Stuttering &normal dysfluencies may be associated with some

difficulty in central auditory processing.

In contrast to these studies Guitar (1987) found no differences

between stutters &non stutters on the SSI-ICM,but stutters in theirstudy had all recently completed a treatment program.

This finding intriguing in light of evidence from brain imaging

studies that individual who stutter who had demonstrated anabsence 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


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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 listner.

Hall & Jerger(1962)stated that stutterers &nonstutterers

significantly differed in their total correct responses to thecompeting portion of the test.

Stutterers performed poorly on this test when compared to non

stutteres.

Another tool for assessing central auditory processing is the

masking level difference test(MLD) ,which requires listeners to

detect the onset &offset of a tone in the presence of masking noise.KUNNAMPALLIL GEJOJOHN,MASLP


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When masking noise is played in the same ear as the tone ,there

are fewer cues for listeners to use in filtering the tone from the

masking tone.

Listeners 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 to support the

outcome of the SSI studies because both tests require theparticipants to use temporal informationin 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 . KUNNAMPALLIL GEJOJOHN,MASLP


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Two other studies of 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.

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 durationsof tones & silent intervals .

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JOHN,MASLP


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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 thanmore fluent participants.

In addition ,more disfluent subjects in both groups judged

temporal intervals to be longer than less disfluent subjects.

It has been suggested that fear &anxiety affect temporal processing

(Fraisse, 1963) and that anomalies in temporal processing may bean underlying cause of both stuttering (Kent 1984 ) and high levels

of normal disfluency(Wynne1982).

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Therefore, the 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

KUNNAMPALLIL GEJO

JOHN,MASLP


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(3) Dichotic listening tests :

In the early studies, a procedure was developed to assesshemispheric 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 hemispherecarry more information to the hemisphere on the opposite side

than to the hemisphere on the same side .

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JOHN,MASLP


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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 donot show the typical R ear advantage that nonstutters do, which is

evidence that people who stutter do not have Lt hemisphere

dominance for language (Blood 1985;&Moore 1975).

Some dichotic studies found no difference between stutters

&nonstutters (Dorman 1975&Pinksy &McAdams ,1980).

KUNNAMPALLIL GEJO

JOHN,MASLP


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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 tobe on a continuum rather than simply present or absent.

More severe or neurologically involved stutters may have more

abnormal auditory processing .

Researches view stuttering as disorder in the control of seqence &

timing .

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JOHN,MASLP


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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 tophonation ,there by reducing the amplitude of the ear drum

vibration & alternates the hearing of ones own speech .

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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 to the external

sound in stutterers &controls.

Reflex threshold was equivalent was in 2groups, but reflex

amplitude was smaller in stuttering group.

Hannley and Dorman (1982) observed no difference in the latency

or amplitude of the reflex.

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March banks &El-Yaniv(1986) found no difference between

stutterers and normal speakers in middle ear muscle activity during

vocalization .

(3)Auditory processing of an about to be produced word

facilitates its correct production

Stutterers often release them from a block when someone elseword 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)

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(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.

(4) Brain electrical potentials :

Studies of electrical brain activity in response to auditory

stimuli have provided further evidence that auditory processing is

abnormal in individuals who stutter.KUNNAMPALLIL GEJOJOHN,MASLP

M l d L (1983) f d h h d f k


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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 first study found stutters responses to be slower than

nonstutters responses & the second study found them to be faster

than non stutters responses .

A study of Molt(1997) is more relevant to the question raised by the

brain imaging studies of whether person who stutter have a deficit

in the left auditory cortex.KUNNAMPALLIL GEJO

JOHN,MASLP


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Molt found that stutters have longer latencies & lower amplitudes

of brain waves in the in the cortex when they where asked to

make decisions about semantic incongruencies in sentences theylistened 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 latenciesbut greater amplitude of wave I for stutterers .

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JOHN,MASLP


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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 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.

KUNNAMPALLIL GEJO

JOHN,MASLP

b f h i d b h h l i i f h


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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 adultstutters 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 possiblegenerators for the MLR waves.

The difference may lead to poor temporal processing

&programming in stutterers .KUNNAMPALLIL GEJOJOHN,MASLP

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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

major sites of generation of the P300 response (Rogers et al 1991)

Blood (1991) tested stutterers using P300 and found no differencesbetween stutterers and nonstutterers in the latency of p300.

16 young adult males aged 17 to 36 years with Rt handed

compared with stutterers and found that stutterers exhibitedrelatively lower amplitude P300s in the right hemisphere.

This may be interpreted as possibility that altered cerebral

dominance plays an important role.KUNNAMPALLIL GEJOJOHN,MASLP


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Stuttering and auditory functions..pdf/ KUNNAMPALLIL GEJO