Assess Prof. Fawzia Al-Rouq Department of PhysiologyCollege of MedicineKing Saud University

Physiology of LanguagePhysiology of Language

PhysiologyPhysiology of Languageof Language

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

Physiology of LanguagePhysiology of Language

The primary brain areas concerned with language The primary brain areas concerned with language

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

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

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

Anatomy of language areas

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

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

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

Location of language areas

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

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

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

AphasiasAphasias

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

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

Fluent, nonfluent, and anomic aphasias.Fluent, nonfluent, and anomic aphasias.

In nonfluent aphasia (EXPRESSIVE APHASIA, ANTERIOR APHASIA)

the lesion is in Broca’s areathe lesion is in Broca’s area

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

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

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

Fluent AphasiaFluent Aphasia ( ( RECEPTIVE APHASIA, RECEPTIVE APHASIA, POSTERIOR APHASIA) POSTERIOR APHASIA)

Lesion in the wernicke’s areaLesion in the wernicke’s area

Speech itself is normal and sometimes the Speech itself is normal and sometimes the patients talk excessively. patients talk excessively.

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

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

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

anomic aphasiaanomic aphasia

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

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

Type of Aphasia andType of Aphasia andSite of LesionSite of Lesion

Characteristic NamingCharacteristic NamingErrorsErrors

Nonfluent (Broca’s area)Nonfluent (Broca’s area)

Fluent (Wernicke’s area)Fluent (Wernicke’s area)

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

Anomic (angular gyrus)Anomic (angular gyrus)

““Tssair”Tssair”

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

““Flair . . . no, swair . . . Flair . . . no, swair . . . tair”tair”

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

Aphasias. Characteristic responses ofAphasias. Characteristic responses ofpatients with lesions in various areas whenpatients with lesions in various areas when

shown a picture of a chairshown 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

DyslexiaDyslexia which is a broad term applied to impaired ability which is a broad term applied to impaired ability

to read, due to an inherited abnormality.to read, due to an inherited abnormality.

Causes of Dyslexia:Causes of Dyslexia:

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

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

3.3. There is decreased blood flow in angular There is decreased blood flow in angular

gyrus in categoricalgyrus in categorical hemisphere in both hemisphere in both cases.cases.

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.

Lesions limited to the left temporal poleLesions limited to the left temporal pole (area 38) cause inability to retrieve names (area 38) cause inability to retrieve names of places and persons but preserves the of places and persons but preserves the ability to retrieve common nouns.ability to retrieve common nouns.

StutteringStuttering, associated with right cerebral , associated with right cerebral dominance and widespread overactivity dominance and widespread overactivity in the cerebral cortex, cerebellum andin the cerebral cortex, cerebellum and supplementary motor area.supplementary motor area.

An important part of the visual input goes to the An important part of the visual input goes to the inferior temporal lobe, where representations of inferior temporal lobe, where representations of objects, particularly faces, are stored.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 Lesions in this area cause prosopagnosiaprosopagnosia, the , the inability to recognize faces. inability to recognize faces.

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

However, they cannot identify the familiar faces However, they cannot identify the familiar faces they see.they see.

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.

In the inferior portion of the left frontal In the inferior portion of the left frontal lobe there is an area concerned with lobe there is an area concerned with number facts and exact calculations. number facts and exact calculations.

Frontal lobe lesions can cause Frontal lobe lesions can cause acalculia, a selective impairment of acalculia, a selective impairment of mathematical abilitymathematical ability..

Accurate navigation in humanAccurate navigation in human

1.One is the 1.One is the right hippocampusright hippocampus, which is , which is concerned with learning where places are concerned with learning where places are located, located,

2.and the other is the 2.and the other is the right caudate right caudate nucleusnucleus, which facilitates movement to , which facilitates movement to the places.the places.

The greater brain weight of men is due to The greater brain weight of men is due to more neural components involved in more neural components involved in getting from place to place and that this is getting from place to place and that this is why men resist asking directions when why men resist asking directions when lost, whereas women do not hesitate to lost, whereas women do not hesitate to seek help.seek help.

Brain Areas Concerned with Language

• Wernick’s Area

• Broca’a Area

• Speech articulation Area in Insula

• Motor Cortex

• Angular Gyrus

ANOMIC

NON FLUENT

GLOBAL

APHASIA

FLUENT

BROCA'S AREA

• WERNICK’S AREA CONDUCTION APHASIA

ANGULAR GYRUS

WIDESPREAD DAMAGE TO SPEECH AREAS

EXPRESSIVE RECEPTIVE

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