PHYSIOLOGY OF LANGUAGE

& SPEECH

By Ramesh Nayak

M.Sc. Physiology IIIrd

Contents

• History

• Introduction

• Organs of speech

• Development of speech

• Type of speech

• Language & speech areas in brain

• Neurophysiology of language & speech

• Mechanism of speech

• Applied aspects

• Recent advance

• References

History

• Paul Broca (1824-1880):

-discovered Broca's area,

• Carl Wernicke (1848-1904):

-discovered Wernicke's area,

• Henry Head ( 1926 ):

-Pioneer scientist in field of speech

disorders & first one to classify

aphasia

Introduction

• To understand spoken & printed words & to

express ideas in speech & writing called

language

• Expression of thought by production of articulate

sound, bearing a definite meaning called speech

• When sound produced verbally called speech

• If it expressed by visual symbol known as

writing

• If visual symbols or written words expressed

verbally becomes reading

Organs of speech

Development of speech

First stage:-

• Occurs association of certain words with

visual, tactile, auditory & other sensations,

aroused by object in external world, which is

stored in memory

Second stage:-

• When a definite meaning has been attached to

certain words

• Pathway between auditory area (41) & motor

area for muscle of articulation which help in

speech (44) is established

Role of cortical areas in the Development

of speech

Involve integration of three important areas of cerebral cortex-

• Wernicke area – speech understanding

• Broca area – speech synthesis

• Motor area – activation of peripheral speech

apparatus

Type of speech

Two major types of

speech are recognized-

• Spoken speech

- Means understanding thespoken words & expressingideas in speech

• Written speech

- Means understandingwritten words & expressingideas in writing

Language & speech areas in brain

Dejerine’sarea

Exner areaReceptive areas-

Wernicke’s area-

• for processing sensory

information from somatic

sensory, visual & auditory

cortices

Angular Gyrus-

• also called Dejerine’s area

• This subserves perception of

written language.

Cont….

Exner area

Executive or Expressive Areas

Broca’s area

• Regulate the function of muscle of

lips, tongue, pharynx & larynx

Exner writing area

• Visually perceived word are given

expression in writing through this

area

Arcuate Fasciculus

• Coordinates understanding &

execution of speech & language

skills

Neurophysiology of language & speech

There are two aspects of communication

• Language input ( sensory aspect )

- Includes visual, auditory & proprioceptive

impulses

• Language output ( motor aspect )

- Includes mechanism concerned with expression

of spoken (sound) language & written language

Components of sound based language

Include:-

• Phonemes

• Morphemes

• Words

• Lexicon

• Syntax

• Semantic

• Discourse

• Progody

Wernicke’s theory of Language

• Theory was formulated on the basis of defectin language, observe in patients with lesiondifferent part of cortex

• According to this theory, utterance arises inWernicke’s area & passed to Broca’s area viaarcuate fasciculus

• After sentence is formulated in Broca’s area

• It is transferred to motor cortex, wherearticulation is programmed by activation ofappropriate muscle in mouth & face

Mechanism of speech

Can be described separately for

spoken speech

• Understanding of speech

written speech

spoken speech

• Expression of speech

written speech

Understanding of spoken speech

By following activities-

i. Hearing of spoken words requires auditory pathway

from ears to primary auditory area

• Primary auditory area include Brodmann’s area

(41&42) & form center for hearing

Connections-

• Afferents are received from medial geniculate body (via

auditory radiation) & pulvinar of thalamus

• Efferents are sent to medial geniculate body, superior

colliculus & pulvinar

Cont…

Functions-

• This area perceives nerve impulses as sound,i.e. auditory information such as loudness,pitch, source & direction of sound

ii. Recognition & understanding of spoken wordsis carried by auditory association area (21 &20)

• These area receive impulses from primary area& concerned with interpretation & integrationof auditory impulses

iii. Interpretation & comprehension of speechideas involves activities of Wernicke’s area

Understanding of written speech

By following activities-

i. Perception of written words requires intactvisual pathway from eyes to primary visualcortex

• Primary visual cortex (17) is concernedwith perception of visual impulses

ii. Interpretation of written speech by visualassociation area (18&19) involved inrecognition & identification of written words

iii. Generation of thoughts/ideas in response towritten speech involve Dejerine area

Expression of spoken speech

1 2

3

5

6

4

Expression of spoken & written speech

1

2

9

8

7

5

63

Dejerine areaExner’s area

4

Theory of speech production

Role of cortical areas in control of speech

Cortical areas functions

Motor areas

Broca area (44 & 45) Control movement of structure involve in

speech

Upper frontal motor

areas

Controls movements involve in writing

Sensory areas

Secondary auditory area

(22)

Concerned with interpretation of auditory

sensation

Concerned with storage of memory of

spoken words

Secondary visual area

(18)

Concerned with interpretation of visual

sensation

Concerned with storage of memory of

visual symbols

Wernicke area

Concerned with interpretation of auditory

sensation

Concerned with understanding auditory

information & sending it to Broca area

Concept of dominant hemisphere for

language

• Approximately 95% of all individuals, left

hemisphere is dominant

• Since, motor area concerned with hand movement

is closely associated with center for speech

• This explain right handedness in over 90%

individual

• 70% of left handed people also have left

hemisphere dominance

• 15% of left handed show right dominancy

• The remaining are mixed dominancy

Cont….

• Presently is believed that left hemisphere is not reallydominant over right hemisphere

• In fact, two halves of brain have Independentcapabilities of control of motor activities & speech

• By connection of two halves of brain informationstored in one hemisphere available to other

• Therefore the terms dominant & non dominant arereplaced by categorical & representationalhemisphere respectively

Functions allotted to left hemisphere in

right handed person

• Right hand control

• Spoken language

• Written language

• Mathematical skills

• Scientific skill

• reasoning

Functions allotted to right hemisphere in

right handed person

• Left hand control

• Music awareness

• Three dimensional awareness

• Art awareness

• Insight

• imagination

Applied aspects

• General

• Speech disorder

i. Aphasia

ii. Anarthria or dysarthria

iii. Dysphonia

iv. Stammering

Cont….

Types of aphasia-

• Motor aphasia

• Sensory aphasia

• Global aphasia

• Dissociative language syndrome

Dissociative language syndrome

• Refer to language deficit that do not resultfrom lesion of cortical language areas, butfrom disruption of pathways joining them

• Included in this category are-

Conduction aphasia

Pure word deafness

Pure word blindness

Pure word mutism

Anomic aphasia

Transcortical aphasia

Cont…

Head’s classification of aphasia

Types of aphasia Features

Verbal aphasia Inability in formation of

words

Syntactical

aphasia

Inability to arrange words in

proper sequence

Semantic aphasia Inability to recognize the

significance of words

Nominal aphasia Inability to name the familiar

objects

Features & causes of different types of aphasia

Type of Aphasia Features Cause

Broca’s aphasia Non-fluent speech problem Lesion in Lt. frontal lobe

Wernicke’s

aphasia

Speech without any meaning Lesion in Lt. temporal lobe

Global aphasia Combined features of Broca

aphasia & Wernicke aphasia

Widespread lesion in speech

areas of Lt. cerebral

hemisphere

Nominal aphasia Inability to name the familiar

object

Lesion in post. Temporal &

inferior parietal gyri

Motor aphasia Difficult in uttering individual

words

Defect in pathway between Lt.

speech center & precentral

cortex

Auditory aphasia Inability to understand spoken

words

Lesion in secondary auditory

area

Visual aphasia Inability to understand written

symbol

Lesion in secondary visual area

Agraphia Inability to write Defect in pathway between

cortical areas concerned with

writing

Recent advance

• The development & introduction of new

physiological instruments for investing various

aspects of articulatory function in a person

with dysarthria included :

• Electromagnetic articulography (EMA)

• Electropalatography

References

• GUYTON & HALL-TEXT BOOK OF MEDICAL PHYSIOLOGY

( 12th Edition, Page- 697-704 )

• INDU KHURANA-TEXT BOOK OF MEDICAL PHYSIOLOGY

( 1st Edition, Page- 1125-1128 )

• A. K. JAIN- TEXT BOOK OF MEDICAL PHYSIOLOGY

( 5th Edition, Page- 1067-1071)

• G.K.PAL- TEXT BOOK OF MEDICAL PHYSIOLOGY

( 2nd Edition, Page- 922-927)

• WILLIAM F GANONG- REVIEW OF MEDICAL PHYSIOLOGY

( 22nd Edition, Page-266-277)