Dr Raghuveer Choudhary Asstt. Prof. Department of PhysiologyDr S.N.Medical CollegeJodhpur

Physiology of Language and speech

Language is one of the fundamental bases of human intelligence and a key part of human culture.

To understand the spoken & printed words & to express ideas in speech & writing is called Language.

Physiology of Language

Language: refers to vocabulary & syntax independent of mode of production or comprehension

Speech: actual production or writting

Vocalization: production of sound without linguistic content

Types of speech

1. Spoken speech:

understanding spoken words & expressing ideas in speech

2. Written speech:

understanding written words and expressing ideas in writing

Categorical Hemisphere Representational Hemisphere

Functions alloted to left hemishere in right handed person

Right hand control Spoken language Written language Mathematical skills Scientific skills Reasoning

Functions alloted to right hemishere in right handed person

Left hand control Music awareness Art awareness 3 dimensional

awareness Imagination insight

Cerebral Dominance

Categorical hemisphere- analytic processes Representational hemisphere- visuospatial

relations 90% left hemisphere is categorical 70% of left handed have left hemisphere

dominance

Language areas of brainBroca’s area: anterior speech areaLocation- 3rd frontal gyrusDetailed and co-ordinated pattern of vocalization

Important Areas for Language

The primary brain areas concerned with language

are arrayed along and near the sylvian fissure (lateral cerebral sulcus) of the categorical hemisphere.

A region at the posterior end of the superior temporal gyrus called Wernicke’s area is concerned with comprehension of auditory and visual information.

It projects via the arcuate fasciculus to Broca’s area (area 44) in the frontal lobe.

Anatomy of language areas

Important Areas for Language

Exners Area

Dejerine area

Wernicks area

Broca’s area processes the information received from Wernicke’s area into a detailed and coordinated pattern for vocalization

and then projects the pattern via a speech articulation area in the insula to the motor cortex, which initiates the appropriate movements of the lips, tongue, and larynx to produce speech.

The angular gyrus behind Wernicke’s area appears to process information from words that are read in such a way that they can be converted into the auditory forms of the words in Wernicke’s area.

Location of language areas

Brain Areas Concerned with Language

Wernick’s Area(22) Broca’a Area(44,45) Motor writing area(Exners Area)(6) Motor Cortex Angular Gyrus(Dejerine Area)(39)

Broca’s and Wernicke’s: Summary

Lesion (injury) studies: Show that a brain area is necessary for a given task Without Broca’s area, you can’t produce speech Without Wernicke’s area, you can’t understand speech

If you lose these areas, you lose languageWhen you use language, you use those areas

Types of speech

1. Spoken speech:

understanding spoken words & expressing ideas in speech

2. Written speech:

understanding written words and expressing ideas in writing

Mechanism of speech

Primary auditory cortex/primary visual area

Auditory/visual association areas

Dejerine’s area

Wernicke’s area

Arcuate fasciculus

Broca’s area

Exner’s area

Motor area

Vocalization/Writing

The probable sequence of events when a subject names a visual object(horizontal section of hum-an brain)

It is interesting that in individuals who learn a second language in adulthood,

fMRI reveals that the portion of Broca’s area concerned with it is adjacent to but separate from the area concerned with the native language.

However, in children who learn two languages early in life, there is only a single area involved with both.

Speech/Language Disorders

Aphasias: Abnormalities of language functions not due to defects of vision, hearing or motor system

Classification:

1. Fluent aphasia

2. Non-fluent aphasia

3. Anomic aphasia

Aphasias

Aphasias are abnormalities of language functions that are not due to defects of vision or hearing or to motor paralysis. They are caused by lesions in the categorical hemisphere.

The most common cause is embolism or thrombosis of a cerebral blood vessel.

Fluent(sensory), nonfluent (motor), and anomic aphasias.

In nonfluent aphasia (EXPRESSIVEAPHASIA,MOTOR APHASIA)

the lesion is in Broca’s area

Speech is slow, and words are hard to come by.

Patients with severe damage to this area are limited to two or three words with which to express the whole range of meaning and emotion.

The words retained are those which were being spoken at the time of the injury or vascular accident that caused the aphasia.

Paul Broca and “Tan”

In 1861, Broca examined a patient nicknamed “Tan,” after the syllable he said most often.

The area of damage in Tan’s case is now known as “Broca’s area.”

Broca’s area: crucial for speech production

Tan’s brain: lesion (injury) in left frontal cortex

Paul Broca (1861): patient "Tan”• Severe deficit in speech production: could only say

“tan”• Good language comprehension

Nonfluent aphasia (Motor aphasia):

Slow & effortful

No grammar

Telegraphic speech

Incorrect writing/agraphia

Good comprehension

Nonfluent aphasia (Motor aphasia): Broca’s area contains memories of the sequences

of muscular movements that are needed to articulate words

Often become frustrated by their inability to speak correctly; however, comprehension is not perfect

Difficulty in comprehending meaning from word order (“The horse kicks the cow” vs. “The cow kicks the horse”)

Nonfluent aphasia (Motor aphasia): 3 major speech deficits with Broca’s aphasia:

Agrammatism – difficulty in comprehending or properly employing grammatical devices, such as verb endings and word order

Anomia – difficulty in finding (remembering) the appropriate word to describe an object, action, or attribute

Difficulty with articulation – mispronounce words, often realizing it afterwards, and trying to correct it

Fluent Aphasia ( RECEPTIVE APHASIA, SENSORY APHASIA)

Lesion in the wernicke’s area

Speech itself is normal and sometimes the patients talk excessively.

However, what they say is full of jargon and neologisms that make little sense.

The patient also fails to comprehend the meaning of spoken or written words.

SENSORY APHASIA

Difficulty in understanding the meaning of speech

Motor speech is intact,so patient talk fluently Anomia-inability to find an appropriate word to

express a thought Neologism-creating new words or meaning for

established words Impairment in reading and writing

Speech comprehension

Must not just recognize words, we must understand their meaningWernicke’s area contains neural circuits that accomplish this task

Wernicke’s aphasia – a form of aphasia characterized by poor speech comprehension and fluent but meaningless speech

Comprehension tested by directing movement toward objects asked about by experimenter is also poor (e.g. “Point to the ink bottle” – patient cannot point to ink bottle)However, patients seem unaware of their deficit, unlike with Broca’s aphasia

They do not recognize that their speech is faulty, nor that they do not comprehend other speech

Wernicke suggested that this area is a location where memories of the sequences of sounds that constitute words are stored

Broca’s and Wernicke’s Aphasia

Damage to Wernicke’s area. Speech is fluent, but

meaningless. Comprehension is very

poor. Sound substitutions are

common. Repetition is poor.

Damage to Broca’s area. Speech is not fluent. Comprehension is

affected, but good. Repetition is very poor.

conduction aphasia Lesion in the auditory cortex (areas 40, 41 &42)patients can speak relatively well and have good auditory comprehension but cannot put parts of words together or conjure up words. This is called conduction aphasia because it was thought to be due to lesions of the arcuate fasciculus connecting Wernicke’s and Broca’s areas.

Conduction Aphasia

Damage to arcuate fasciculus.

Speech production is good.

Comprehension is good.

Sound substitutions are common.

Repetition is poor.

Anomic aphasia:

Injury to angular gyrus

Difficulty in understanding written language and pictures

Global aphasia:

Injury to both broca’s & wernicke’s area

Anomic Aphasia When there is a lesion damaging the angular gyrus.

There is trouble understanding written language or pictures, because visual information is not processed and transmitted to Wernicke’s area.

Type of Aphasia andSite of Lesion

Characteristic NamingErrors

Nonfluent (Broca’s area)

Fluent (Wernicke’s area)

Fluent (areas 40, 41 and 42; conduction aphasia)

Anomic (angular gyrus)

“Tssair”

“Stool” or “choss” (neologism)invented word

“Flair . . . no, swair . . . tair”

“I know what it is . . . I have a lot of them”

Aphasias. Characteristic responses ofpatients with lesions in various areas when

shown a picture of a chair

AREA LESION FAETURES

auditory association areas

word deafness

visual association areas

word blindness called dyslexia

Wernicke's AphasiaGlobal Aphasia

unable to interpret the thought Sensory Aphasia

Broca's Area Causes Motor Aphasia

GLOBAL APHASIA (CENTRAL APHASIA)

This means the combination of the expressive problems of Broca's aphasia and the loss of comprehension of Wernicke's.

The patient can neither speak nor understand language.

It is due to widespread damage to speech areas and is the commonest aphasia after a severe left hemisphere infarct.

Writing and reading are also affected.

Global Aphasia

Damage to Broca’s area, Wernicke’s area and the arcuate fasciculus.

Abilities to speak, comprehend and repeat are impaired.

ANOMIC

NON FLUENT

GLOBAL

APHASIA

FLUENT

BROCA'S AREA• WERNICK’S AREA

CONDUCTION APHASIA

ANGULAR GYRUS

WIDESPREAD DAMAGE TO SPEECH AREAS

EXPRESSIVE RECEPTIVE

Language

Broca’s area: Involves articulation of speech. In damage, comprehension of speech in unimpaired.

Wernicke’s area: Involves language comprehension. In damage, language comprehension is destroyed, but speech is

rapid without any meaning. Angular gyrus:

Center of integration of auditory, visual, and somatesthetic information.

Damage produces aphasias. Arcuate fasciculus:

To speak intelligibly, words originating in Wernicke’s area must be sent to Broca’s area. Broca’s area sends fibers to the motor cortex which directly controls the

musculature of speech.

Dyslexia: Impaired ability to readPhonemic deficitArtists, musicians, mathematicians

Dysarthria:Imperfect vocalizationDefect in motor areas & their connections

Dyslexia which is a broad term applied to impaired ability

to read, due to an inherited abnormality.

Causes of Dyslexia:

1. Reduced ability to recall speech sounds, so there is trouble translating them mentally into sound units (phonemes).

2. There is a defect in the magnocellular portion of the visual system that slows processing and also leads to phonemic deficit.

3. There is decreased blood flow in angular gyrus in categorical hemisphere in both cases.

Brain Activation During Reading

Reader with dyslexia shows less activation of Wernicke’s area and the angular gyrus and more activation of Broca’s area.

DYSARTHRIA

Slurred speech. Language is intactParalysis, slowing or incoordination of muscles of articulation or local discomfort causes various different patterns of dysarthria.

DISORDERED ARTICULATION

Examples • 'gravelly' speech of upper motor neurone

lesions of lower cranial nerves, • jerky, ataxic speech of cerebellar lesions

(Scanning Speech), • the monotone of Parkinson's disease

(Slurred), • speech in myasthenia that fatigues and dies

away. Many aphasic patients are also somewhat dysarthric.

nasal tract

(hard) palate

oral tract

velum (soft palate)

velic port

tongue

tongue tip

pharynx

glottis(vocal folds and

space between vocal cords)

vocal folds (larynx)= vocal cords

alveolar ridge

lips

teeth

The Speech Production Apparatus (from Olive, p. 23)

Acoustic Phonetics: Anatomy

Acoustic Phonetics: Anatomy

Types of phonation (from Daniloff, p. 194)

quietbreathing

forcedinhalation

normalphonation whisper

Recognition of face

Right inferior temporal lobe Prosopagnosia Autonomic changes

An important part of the visual input goes to the inferior temporal lobe, where representations of objects, particularly faces, are stored.

In humans, storage and recognition of faces is more strongly represented in the right inferior temporal lobe in right-handed individuals, though the left lobe is also active.

Lesions in this area cause prosopagnosia, the inability to recognize faces.

They can recognize people by their voices, and many of them show autonomic responses when they see familiar as opposed to unfamiliar faces.

However, they cannot identify the familiar faces they see.

THANK YOU