Physiology of speech

16/11/17 04:05 AM Dr. Chintan Parmar
SPEECH
Speech is one of the ways we
communicate with our environment, to
express our thoughts, memories and
feelings.
It is also an effective way to monitor
normal growth and development
1

LANGUAGE
 To understand spoken and
printed words and to express
ideas in speech and writing is
called language.
 It is an example of skilled
voluntary movements.
2

Anatomical components of theAnatomical components of the
speech system for humanspeech system for human
language.language.
• Sound in human language is
produced by the regulation of
airflow from the lungs through the
throat (vocal cord), nose and mouth.
16/11/1716/11/17 04:05 AM04:05 AM 33Dr. Chintan ParmarDr. Chintan Parmar

 The larynx contains folds of muscle
called the vocal folds (sometimes
called vocal cords).
 The opening between the vocal
folds is known as the glottis.
 These folds can be relaxed, letting air
flow freely through the glottis,
 or tensed, so that the air vibrates as it
passes through the glottis.
 If the folds are only partially closed,
a whispered sound is produced.
16/11/17 04:05 AM 4Dr. Chintan Parmar

Resting Adduction Abduction
.
5

The process of producing speechThe process of producing speech
sounds:sounds:
 The process of producing speech sounds:
lungs: fill with air
contraction of rib cage forces air from the lungs into
the trachea - the volume of air determines the amplitude
of the sound
trachea (windpipe): conveys air to the vocal tract.
The vocal cords, at the top of the trachea, separate the
trachea from the base of the vocal tract
 vocal tract consists of:
 pharynx (throat)
 mouth
 nose
 the tongue, teeth and lips
 the shape of the vocal tract determines the type of
speech sound - e.g., the /a/ in "hat" vs the /i/ in "hit
6

 Speech differs from breathing in that at some
point in the path you set the air in rapid
motion or vibration
Two principal components of speech
production
 Excitation - create a sound by setting the air
in rapid motion
 Vocal tract - "shape" the sound

A. Excitation: three principal forms
1. Phonation: vibration of vocal
cords
2. Frication: Turbulent air flow
3. Plosive: Closure at some
point in the vocal tract,
followed by a release of air
8

Phonation: vibration of vocalPhonation: vibration of vocal
cordscords
 The vocal cords consist of ligament and
muscle, and are adjustable under muscle
control.
 The cartilage surrounding the vocal cords
provides support.
 Vibration
 cords tense, pressed together - no air
flows
 air pressure from the lungs forces them
open
 local pressure is reduced --> cords close
 the cycle repeats
9

 The result is a periodic release of air into the
pharynx.
 The fundamental frequency of the vocal cord
opening/closing cycle becomes the fundamental
frequency (informally, the "pitch") of the resulting sound.
 The tenser the vocal cords
- the higher the pitch
- the shorter the period
 Typical frequency of vocal cord open/close cycle:
 male: 128 Hz
 female: 256 Hz

16/11/17 04:05 AM Dr. Chintan Parmar 11

Neurophysiology of Speech andNeurophysiology of Speech and
LanguageLanguage
16/11/1716/11/17 04:05 AM04:05 AM 1212Dr. Chintan ParmarDr. Chintan Parmar

Speech Structures in the Brain
 Wernicke's Area: Auditory association area.
Language comprehension and formulation (both
spoken and written)
 Dejerine Area : Visual speech center
 Broca's Area: Speech production and
comprehension. Pre-motor speech planning.
 Exner’s Area : Motor writing center
 Arcuate fasciculus: Pathway interconnecting
Broca's Area and Wernicke's area.
 Supplementary Motor Cortex: Seems to be related
to word finding, rhythm, phonation, articulation.

Brain Asymmetries in Speech andBrain Asymmetries in Speech and
LanguageLanguage
 Dominant Left Hemisphere
 The left hemisphere is generally considered
to be the language dominant
(categorical) hemisphere.
 The non-dominant (Representational) or
right hemisphere is believed to be
responsible for the expression of feelings
such as joy, sorrow, anger, depression,
delight.
 It is also important in the production of
speech prosody which is a component of
how we signal emotion in speech.
 Spatio-temporal Relations such as recognition
of face, identification of object
14

Categorical Hemi.
 For categorization
and symbolization.
 Lesion produce
 Language
disorder
 Patient is disturbed
 Loss of recent
verbal memory
Representational
Hemi.
 Recognition of face,
identification of
object, musical
themes.
 Lesion produce
 Astereognosis
 Agnosia
 Patient not disturbed
 Loss of Recent visual
memory
15

Cerebral Dominance forCerebral Dominance for
Language and Left and Right-HandednessLanguage and Left and Right-Handedness
 Right-handed individuals have a
98% probability of left hemisphere
dominance for language
 Left-handed individuals show a
much more complex pattern.
 For these people, both hemispheres
are involved in language processing
16

Cerebral Dominance forCerebral Dominance for
Language and Anatomical AsymmetryLanguage and Anatomical Asymmetry
 There is some evidence for
anatomical asymmetry of some
language areas.
 The left hemisphere Wernicke's
Area is said to be larger than the same
structure on the right side.
 This is true for a majority of right
handers but not so for majority of left
handers.
17

What about language comprehension?What about language comprehension?
Where is the most logical place to put theWhere is the most logical place to put the
comprehension area? (sensory speech)comprehension area? (sensory speech)
 First you must decide if language is primarily
visual or auditory? When you read (written
speech), do you "hear" the words in your head?
 When you listen (spoken speech), do you "see"
the words as written?
 Which came first, written or spoken
language?
 You probably agree that language is more of an
auditory phenomenon than visual.
 As expected, the language comprehension
area is just adjacent to auditory cortex,
where the parietal lobe meets the temporal
lobe.
 This area was discovered by Wernicke in 1874
18

Spoken speechSpoken speech
Ear (sound)
Primary auditory
area(41)
Auditory – psychic
area (21)
Auditory speech area
(22)
20

Written speechWritten speech
Primary visual
area
Visuo-psychic area
Dejerine area
(for internal
speech)
21

MOTOR SPEECHMOTOR SPEECH
 First and foremost, you need fine control
over the tongue and mouth.
 It would make sense to put your cortical
area near the mouth section of motor
cortex.
 Sure enough, just rostral to the motor-
mouth area of the precentral gyrus is a
small area that controls speech.
22

 It is called Broca's area, after the physician who
discovered it in 1861. It is located in the inferior frontal
gyrus. It process the information received from sensory
speech area into detailed and co-ordinate pattern for
vocalization.
 This pattern is than projected to motor cortex which
initiates the appropriate movement of lips, tongue and
larynx to produce speech
 Exner’s area: It is located in the middle frontal gyrus in
dominant hemisphere .
 It process the information from Broca's area into detailed
and coordinated pattern, which then along with motor
cortex initiates the appropriate movements of the hands
and fingers to produce written speech

EXPRESSION OF SPOKEN SPEECHEXPRESSION OF SPOKEN SPEECH
word
Highest area of hearing
(area 41)
Wernicke's area.
Arcuate fasciculus
Broca’s area
Motor area(4)
25

EXPRESSION OF Spoken & writtenEXPRESSION OF Spoken & written
SPEECHSPEECH
Primary visual area
Visual association area
Dejerine area
Wernicke's area.
Arcuate fasciculus
Broca’s area
Motor & Exner’s area
26

Lastly,
 Language is far too complex to be broken down into two
discrete cortical areas. Obviously there are visual and
manual components to language, for reading and writing.
Where does sign language fit in?
 How do you explain a patient whose only deficit is an
inability to name tools? He can describe the use of a
hammer but not its name.
 How does a person's name - trigger the face, personality,
birth date, or voice of that person in your memory?
 Language is probably located all over the brain, with
extensive crosstalk between areas.
 The discrete areas of Broca and Wernicke may be
necessary for language, but they are certainly not
sufficient.
27

Language impairmentLanguage impairment
 Speech impairment may be any of several speech
problems, particularly the following:
 Dysarthria is difficult, poorly articulated speech, such as
slurring.
 Aphasia is impaired expression or comprehension of
written or spoken language.
 Dysarthria is occasionally confused with aphasia.
 It is important to distinguish between a difficulty in
articulation of words versus a problem with the
production of language, as these have different
causes.
28

APHASIAAPHASIA
 Aphasia is loss of communication skills previously
learned and commonly occurs following strokes or in
people with brain tumors or degenerative diseases that
affect the language areas of the brain.
 Aphasia represents a broad class of speech and
language disorders resulting from neurological
damage. Aphasias can be divided into two main types:-
 Expressive (Broca's) aphasia: Affects speech
production and is associated with left hemisphere
frontal lesions
 Receptive (Wernicke's) aphasia: Affects
comprehension and is mainly associated with lesions
in Wernicke's area of the left hemisphere
29

Some additional types ofSome additional types of
aphasiaaphasia
 Conduction aphasia:- resulting from a
disconnection of the language perception anddisconnection of the language perception and
production centresproduction centres usually resulting from a lesion in
the arcuate fasciculus which connects Broca's and
Wernicke's areas
 Such patients are unable to repeat aloud what theyunable to repeat aloud what they
hear.hear.
 Transcortical aphasia:- Don't affect the speech
centres or the connections between them but affect
the connection of the speech centres to the rest of
the brain.
 Word deafness: Disconnecting Wernicke's area
from the auditory cortex
30

 Anomic aphasia:- difficulty naming objects. Pure forms of
this aphasia involve lesions in the angular gyrus.
 It is assumed that this results from a disconnection between
the sensory modalities and the rest of the brain.
 Global aphasia:- Widespread damage resulting in severe
impairment of all language and speech functions.
 Subcortical aphasia:- lesions of the thalamus. Damage
here results in verbal fluency and word repetition problems.
 The thalamus appear to be involved in
 directing attention to verbal input,
 in retrieving information from verbal memory and
 to play some role in the regulation of the activity of speech
producing muscles

 In some cases of aphasia, the
problem eventually resolves
itself, but in others the condition
is irreversible.
 Head trauma
 Alzheimer's disease
 Stroke
 Transient ischemic attack (TIA)
 Brain tumorBrain tumor
32

DYSARTHRIADYSARTHRIA
 Dysarthria is generally apparent in daily conversation
where there is difficulty expressing certain sounds or
words.
 This condition may be caused by taking excess
medications such as narcotics, phenytoin or
carbamazepine.
 Degenerative neurological disorders affecting the
cerebellum or brainstem can also cause dysarthria.
 Stroke that affects brainstem or cerebellar regions
can also cause dysarthria.
 Any facial weakness, such as Bell's palsy or tongue
weakness, can cause dysarthria.
 Poorly fitting denturesPoorly fitting dentures
 Alcohol intoxication
34

Kluver Bucy syndromeKluver Bucy syndrome
 Anterior portion of the temporal lobe is
destroyed in monkeys  amygdala 
changes in the behavior
 Excessive tendency to examine objects
orally
 Loss of fear
 Decreased aggressiveness
 peacefulness
 Changes in the dietary habits
 Psychic blindness
 Excessive sex drive

Physiology of speech

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