Physiology of speech

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Dr Raghuveer Choudhary Asstt. Prof. Department of Physiology Dr S.N.Medical College Jodhpur Physiology of Language and speech

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

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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 : 

Types of speech Spoken speech: understanding spoken words & expressing ideas in speech Written speech: understanding written words and expressing ideas in writing

Categorical Hemisphere Representational Hemisphere : 

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 : 

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 brain : 

Language areas of brain Broca’s area: anterior speech area Location- 3rd frontal gyrus Detailed and co-ordinated pattern of vocalization

Important Areas for Language : 

Important Areas for Language

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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 : 

Important Areas for Language

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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.

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Location of language areas

Brain Areas Concerned with Language : 

Brain Areas Concerned with Language Wernick’s Area Broca’a Area Motor writing area(Exners Area) Motor Cortex Angular Gyrus(Dejerine Area)

Broca’s and Wernicke’s: Summary : 

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 language When you use language, you use those areas

Types of speech : 

Types of speech Spoken speech: understanding spoken words & expressing ideas in speech Written speech: understanding written words and expressing ideas in writing

Mechanism of speech : 

Mechanism of speech Primary auditory cortex/primary visual area Auditory/visual association areas Dejerine’s area Wernicke’s area

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Arcuate fasciculus Broca’s area Exner’s area Motor area Vocalization/Writing

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

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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 : 

Speech/Language Disorders Aphasias: Abnormalities of language functions not due to defects of vision, hearing or motor system Classification: Fluent aphasia Non-fluent aphasia Anomic aphasia

Aphasias : 

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.

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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” : 

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 : 

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

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Nonfluent aphasia (Motor aphasia): Slow & effortful No grammar Telegraphic speech Incorrect writing/agraphia Good comprehension

Nonfluent aphasia (Motor aphasia): : 

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): : 

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

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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 : 

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

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

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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 : 

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.

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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 : 

Conduction Aphasia Damage to arcuate fasciculus. Speech production is good. Comprehension is good. Sound substitutions are common. Repetition is poor.

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Anomic aphasia: Injury to angular gyrus Difficulty in understanding written language and pictures Global aphasia: Injury to both broca’s & wernicke’s area

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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.

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Type of Aphasia and Site of Lesion Characteristic Naming Errors 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 of patients with lesions in various areas when shown a picture of a chair

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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 : 

Global Aphasia Damage to Broca’s area, Wernicke’s area and the arcuate fasciculus. Abilities to speak, comprehend and repeat are impaired.

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ANOMIC NON FLUENT GLOBAL APHASIA FLUENT BROCA'S AREA WERNICK’S AREA CONDUCTION APHASIA ANGULAR GYRUS WIDESPREAD DAMAGE TO SPEECH AREAS EXPRESSIVE RECEPTIVE

Language : 

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.

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Dyslexia: Impaired ability to read Phonemic deficit Artists, musicians, mathematicians Dysarthria: Imperfect vocalization Defect in motor areas & their connections

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Dyslexia which is a broad term applied to impaired ability to read, due to an inherited abnormality. Causes of Dyslexia: Reduced ability to recall speech sounds, so there is trouble translating them mentally into sound units (phonemes). There is a defect in the magnocellular portion of the visual system that slows processing and also leads to phonemic deficit. There is decreased blood flow in angular gyrus in categorical hemisphere in both cases.

Brain Activation During Reading : 

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.

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DYSARTHRIA Slurred speech. Language is intact Paralysis, 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.

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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

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Acoustic Phonetics: Anatomy Types of phonation (from Daniloff, p. 194) quiet breathing forced inhalation normal phonation whisper

Recognition of face : 

Recognition of face Right inferior temporal lobe Prosopagnosia Autonomic changes

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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.

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