speech physiology

7/31/2019 Speech Physiology

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Higher Brain Functions:Physiology of Speech,

Language & Speech disordersReference: chapter 57, Guyton 11th Ed.

Dr. Samina Malik


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Centers for Speech

Mechanisms related to language

(understanding the spoken & printed

words) are mainly localized to

NEOCORTEX.

Speech & other intellectual functions are

well developed in humans.


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Areas with language function in the

dominant / categorical hemisphere:


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Language & Speech related

cerebral areas:


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Motor & Sensory Speech areas:


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Areas for

language comprehension (Wernickes area) &

speech production (Brocas area):


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Physiology of Speech:

Speech Involves:

Respiratory system

Specific speech nervous control systemsin cerebral cortex

Respiratory control centers of brain

Articulation & resonance structures ofmouth & nasal cavities.


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Mechanical functions of SPEECH:

1) Phonation

2) Articulation

3) Resonance


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Phonation:

Larynx is adapted to act as a vibrator.

Vibrating parts are the vocal cords / folds.

They protrude from lateral walls of larynx

towards the center of glottis

They are stretched & positioned by specific

laryngeal muscles.


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Vocal cords during

normal breathing Vs phonation:

Normal breathing:

Vocal cords are wide

open to allow easypassage of air.

Phonation:

Vocal cords move

together so thatpassage of air

between them will

cause phonation.


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Determination of

PITCH of vibration:

Determined by:

Degree of stretch of cords.

How tightly the cords are approximated toone another.

The mass of the edges of the cords.


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Phonation: Function of larynx.

Vocal cords as seen by laryngoscope when

looking into the glottis:


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How vocal cords are stretched?

By either:

Forward rotation of thyroid cartilage.

Or:

Posterior rotation of arytenoid cartilages.


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Role of muscles in forward & posterior

rotation of thyroid & arytenoid cartilages:

Muscles stretch from thyroid & arytenoid cartilages to cricoidcartilage.

Thro-arytenoid muscles located within the vocal cords lateral tovocal ligaments pull the arytenoid cartilages towards the thyroidcartilage loosen the vocal cords.

Slips of muscles within the vocal cords change the shapes &masses of vocal cord edges sharpening of vocal cord edgesemission of high pitched sounds or blunting of vocal cord edgesemission of more bass / low pitched / heavy / deep sounds.

Small laryngeal muscles lie between arytenoid & cricoid cartilages rotate these cartilages inwards or outwards or pull their basestogether or apart (abduct or adduct) to give various configurations ofvocal cords.


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Articulation:

It means formation of words from soundsproduced in larynx.

Major organs of articulation:

Lips

Tongue

Soft palate

Teeth


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Articulation:

Consonants of speech are related to

certain anatomical sites.

When we want to speek p & b, they are

labial (from the lips).

D & t are dental (top of tongue is

approximated behind the teeth).

N is nasal (in nasal obstruction, n cannot

be pronounced).


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Abnormal Articulation in:

In hair-lip defect

In local defect in muscles of articulation

Cleft palate


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Resonance:Related to quality or timbre / character of sound.

Resonance depends on resonating chambers.

Resonators include:

Nasal cavity

Paranasal sinuses Pharynx

mouth

Chest cavity (vocal resonance in chest examination)

Hollow cavities (musical instruments) resonance.

Nasal twang: change in character of sound in nasal obstruction.


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Written speech:

Involves coordinated contraction of small

muscles of hand.

In dominant cerebral hemisphere there are

certain speech areas.

In right handed, speech areas are in left

cerebral cortex.


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Brocas area / motor speech area

/Brodmans area 44:

Location:

Inferior frontal gyrus, anterior to face

representation area in primary motor area.


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Brocas area / motor speech area

/Brodmans area 44:

Function:

Detailed pattern for contraction of musclesof phonation & articulation is formed here.

Then impulses are sent to motor cortex toinitiate these contractions.

It receives impulses from Wernikes areathrough arcuate fasiculus.


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Wernikes area / sensory speech

area / Brodmans area 22:

Location:

Posterior part of superior temporal gyrus.

Posteriorly continues with angular gyrus.


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Wernikes area / sensory speech

area / Brodmans area 22:

Function:

Highly intellectual function.

All spoken or written words are completely

understood here.

Thoughts are formed & words are chosento express these thoughts.

Sentences are made & then impulses fromthis area go to motor speech area through

Arcuate fasiculus.


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Angular gyrus / Brodmans area 39:

Location:

Lower part of parietal lobe, posterior to

Wernikes area. Posteriorly it becomes

continuous with secondary visual area.

Function:

Interpretation of visual information.


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Area for naming of objects:

Location:

Posterior temporal lobe.

Naming mainly involves auditory input.


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Facial recognition area:

Prosophenosia:Inability to recognize faces.

Lesion: extensive damage

on medial undersides ofboth occipital lobes(continuous with visualcortex) & alongmedioventral surfaces oftemporal lobes

(associated with limbicsystem that deals withemotions, behaviorresponse to environment& brain activation).


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Additional parts with role in speech:

Motor cortex.

Basal ganglia.

Cerebellum. Respiratory center.


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Feedbacks to brain:

To check if

we are

expressing

ourthoughts

correctly,

there are

feedbacksto brain.


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Feedbacks for

Spoken Vs Written speech

Spoken speech feedback:

Auditory feedback:

When we speak, we hear feedback goes to brain

to check.

Proprioceptive feedback:

Phonation & articulationinvolve muscles

stimulation of

proprioceptors brain

Written speech feedback:

Visual feedback:

When we write, we see &check.

Proprioceptive feedback:

Writing involves smallmuscles of hand

proprioceptors brain


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Pathway for speaking out heard words Vs

pathway for speaking out written words:

Speaking out heard words:

Q: What is your name?

Received in ears

Impulses along auditorypathway

Auditory cortex

Wernickes area (understood &answer decided) alongarcuate fasiculusBrocasarea motor cortex

muscles of phonation &articulation question isanswered.

Speaking out written words:

Q: What is your name?

We read the question

Written words are received inprimary visual area initial

interpretation of these words insecondary visual areafurther interpretation in angulargyrusWernikes area(understood & answerdecided) along arcuatefasiculusBrocas areamotor cortex muscles ofphonation & articulationquestion is answered.


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Speech Pathways:


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Disorders of speech:

APHASIA Motor / non-fluent aphasia:

Patients feel difficulty inuttering words.

Speech is very slow.

In severe cases, speech islimited to few words.

Sometimes, words spoken arethose that were spoken at thetime of trauma / C.V.A which

led to aphasia. Lesion:Brocas area / motor

speech area.

Sensory / fluent aphasia:

Patients speech is fluent.

Speech appears to be normal.

Patient may talk excessivelybut talk carries little sense.

Thoughts are not expressedcorrectly.

Words chosen are notadequate.

Sentences are not correctlymade.

Lesion:Wernikes area /sensory speech area.


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APHASIAS:

Di d f h


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DYSLEXIA / VISUAL RECEPTIVE

APHASIA / WORD BLINDNESS

Patient can see but is unable to understand

the written words / seen words.

Writing & reading is not normal.

Lesion: Angular gyrus or Visual Association Area.


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GLOBAL APHASIA

Severe type of Aphasia.

Patient is completely demented.

May talk irrelevant.

Lesion: wide-spread, involving Wernikes area,Angular gyrus, part of temporal lobe & Sylvian

fissure.


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DYSARTHRIA

Disordered articulation.

Incoordination of muscles of articulation.

CAUSE:

Cleft palate

Hair-lip

Loosely fitting dentures

Poliomyelitis

Myasthenia gravis

Motor neuron

Cerebellar disease

Tongue tie


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DYSPHONIA / HOARSENESS OF VOICE

CAUSE:

Chronic laryngitis

Papilloma of vocal cords Damage to recurrent laryngeal nerve

Hysteria (psycho-neurosis)

Myxoedema (hypothyroidism)


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STAMMERING / STUTTERING

Speech is not fluent.

Speech rhythm is interrupted by:

Arrest

Repetition

Prolongation of certain words / syllables /phrases

Stammering attracts the attention of others.

May occur in normal people during emotionalstress.


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Risk Factors for Stammering:

Very strong familial tendency

Incomplete cerebral dominance (someareas controlling speech are not

developed) Environmental factors (very strict

discipline)

Aggravated by rapid speech, answeringquestions, talking to superiors & duringemotional states / anxiety / nervousness.


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Mechanism of

Normal Vs Stammering speechNORMAL SPEECH:

Laryngeal reflexes(adduction of vocal cords)& voluntary action of

speech (forcefulexpiration) arecoordinated or laryngealreflexes are pre-set justbefore voluntary action of

speech. Any defect in this

coordination results intostammering.

STAMMERING SPEECH

In people who stammer, thereis no stammering duringsinging or recitation, because

in singing & recitation, thereis coordination.

speech physiology

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