Physiology of speech

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MBBS PHYSIOLOGY LECTURE

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  • Wernicke-geschwind model of aphasiaBroca’s area: speech productionWernicke’s area: speech comprehensionArcuatefasiculus: one-way path connection Wernicke’s area to Broca’s areaFirst figure: person asked to repeat a wordProcessing thru brain thought to be this –Auditory cortex (to hear sounds of spoken word)Wernicke’s area (understand word)Arcuate fasciculus (travels to broca’s area)Broca’s area (plan for forming word – which parts of mouth to move when)Motor cortex2nd figure: person asked to read a wordProcessing thru brain thought to be this –Similar route, expect starts with visual cortex instead of auditoryVisual cortexAngular gyrus (associates visual image with sounds of word)Rest is the sameThis model predicts most of the symptoms of different aphasias, but imaging studies suggest more cortex used than just this, esp
  • In 1861, Broca examined a patient nicknamed “Tan,” after the syllable he said most often.He seemed able to understand most things said to him, but he couldn’t speakThe area of damage in Tan’s case is now known as “Broca’s area.”Broca’s area assumed to have something to do with producing language
  • Physiology of speech

    1. 1. Dr Raghuveer Choudhary Asstt. Prof.Department of PhysiologyDr S.N.Medical CollegeJodhpurPhysiology of Language andspeech
    2. 2. Language is one of the fundamentalbases of human intelligence and akey part of human culture.To understand the spoken & printedwords & to express ideas in speech& writing is called Language.Physiology of Language
    3. 3. Language: refers to vocabulary & syntaxindependent of mode of production orcomprehensionSpeech: actual production or writtingVocalization: production of sound withoutlinguistic content
    4. 4. Types of speech1. Spoken speech:understanding spoken words & expressingideas in speech2. Written speech:understanding written words and expressingideas in writing
    5. 5. Categorical Hemisphere Representational Hemisphere Functions alloted to left hemishere inright handed person Right hand control Spoken language Written language Mathematical skills Scientific skills Reasoning Functions alloted to righthemishere in right handed person Left hand control Music awareness Art awareness 3 dimensionalawareness Imagination insight
    6. 6. Cerebral Dominance Categorical hemisphere- analytic processes Representational hemisphere- visuospatialrelations 90% left hemisphere is categorical 70% of left handed have left hemispheredominance
    7. 7. Language areas of brainBroca’s area: anterior speech areaLocation- 3rd frontal gyrusDetailed and co-ordinated pattern of vocalization
    8. 8. Important Areas for Language
    9. 9. The primary brain areas concerned with languageare arrayed along and near the sylvian fissure(lateral cerebral sulcus) of the categoricalhemisphere. A region at the posterior end of the superiortemporal gyrus called Wernicke’s area isconcerned with comprehension of auditory andvisual information.It projects via the arcuate fasciculus to Broca’sarea (area 44) in the frontal lobe.Anatomy of language areas
    10. 10. Important Areas for Language
    11. 11. Exners AreaDejerine areaWernicks area
    12. 12. Broca’s area processes the information received fromWernicke’s area into a detailed and coordinated pattern forvocalization and then projects the pattern via a speech articulationarea in the insula to the motor cortex, which initiates theappropriate movements of the lips, tongue, and larynx toproduce speech.The angular gyrus behind Wernicke’s area appears toprocess information from words that are read in such away that they can be converted into the auditory forms ofthe words in Wernicke’s area.
    13. 13. Location of language areas
    14. 14. 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)
    15. 15. 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 speechIf you lose these areas, youlose languageWhen you use language, youuse those areas
    16. 16. Types of speech1. Spoken speech:understanding spoken words & expressingideas in speech2. Written speech:understanding written words and expressingideas in writing
    17. 17. Mechanism of speechPrimary auditory cortex/primary visual areaAuditory/visual association areasDejerine’s areaWernicke’s area
    18. 18. Arcuate fasciculusBroca’s areaExner’s areaMotor areaVocalization/Writing
    19. 19. The probablesequenceof eventswhen a subjectnamesa visual object(horizontalsection of hum-an brain)
    20. 20. It is interesting that in individuals wholearn a second language in adulthood,fMRI reveals that the portion of Broca’sarea concerned with it is adjacent to butseparate from the area concerned with thenative language. However, in children who learn twolanguages early in life, there is only a singlearea involved with both.
    21. 21. Speech/Language DisordersAphasias: Abnormalities of languagefunctions not due to defects of vision,hearing or motor systemClassification:1. Fluent aphasia2. Non-fluent aphasia3. Anomic aphasia
    22. 22. Aphasias Aphasias are abnormalities of languagefunctions that are not due to defects of vision orhearing or to motor paralysis. They are causedby lesions in the categorical hemisphere. The most common cause is embolism orthrombosis of a cerebral blood vessel. Fluent(sensory), nonfluent (motor), and anomicaphasias.
    23. 23. 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 arelimited to two or three words with which toexpress the whole range of meaning and emotion.The words retained are those which were beingspoken at the time of the injury or vascularaccident that caused the aphasia.
    24. 24. Paul Broca and “Tan” In 1861, Broca examineda patient nicknamed“Tan,” after the syllablehe said most often. The area of damage inTan’s case is now knownas “Broca’s area.”
    25. 25. Broca’s area: crucial for speech production Tan’s brain: lesion (injury) in left frontal cortexPaul Broca (1861): patient "Tan”• Severe deficit in speech production: could only say “tan”• Good language comprehension
    26. 26. Nonfluent aphasia (Motor aphasia):Slow & effortfulNo grammarTelegraphic speechIncorrect writing/agraphiaGood comprehension
    27. 27. Nonfluent aphasia (Motor aphasia): Broca’s area contains memories of the sequencesof muscular movements that are needed toarticulate words Often become frustrated by their inability to speakcorrectly; however, comprehension is not perfect Difficulty in comprehending meaning from wordorder (“The horse kicks the cow” vs. “The cowkicks the horse”)
    28. 28. Nonfluent aphasia (Motor aphasia): 3 major speech deficits with Broca’s aphasia: Agrammatism – difficulty in comprehendingor 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 – mispronouncewords, often realizing it afterwards, and tryingto correct it
    29. 29. Fluent Aphasia ( RECEPTIVE APHASIA, SENSORYAPHASIA)Lesion in the wernicke’s areaSpeech itself is normal and sometimes thepatients talk excessively. However, what they say is full of jargon andneologisms that make little sense.The patient also fails to comprehend themeaning of spoken or written words.
    30. 30. SENSORY APHASIA Difficulty in understanding the meaning ofspeech Motor speech is intact,so patient talk fluently Anomia-inability to find an appropriate word toexpress a thought Neologism-creating new words or meaning forestablished words Impairment in reading and writing
    31. 31. Speech comprehensionMust not just recognize words, we mustunderstand their meaningWernicke’s area contains neural circuitsthat accomplish this task
    32. 32. Wernicke’s aphasia – a form of aphasia characterized by poorspeech comprehension and fluent but meaningless speechComprehension tested by directing movement toward objectsasked about by experimenter is also poor (e.g. “Point to the inkbottle” – patient cannot point to ink bottle)However, patients seem unaware of their deficit, unlike withBroca’s aphasiaThey do not recognize that their speech is faulty, nor thatthey do not comprehend other speechWernicke suggested that this area is a location where memoriesof the sequences of sounds that constitute words are stored
    33. 33. Broca’s and Wernicke’s Aphasia Damage to Wernicke’sarea. Speech is fluent, butmeaningless. Comprehension is verypoor. Sound substitutions arecommon. Repetition is poor. Damage to Broca’s area. Speech is not fluent. Comprehension isaffected, but good. Repetition is very poor.
    34. 34. conduction aphasiaLesion in the auditory cortex (areas 40, 41&42)patients can speak relatively well and havegood auditory comprehension but cannot putparts of words together or conjure up words.This is called conduction aphasia because itwas thought to be due to lesions of thearcuate fasciculus connecting Wernicke’s andBroca’s areas.
    35. 35. Conduction Aphasia Damage to arcuatefasciculus. Speech production isgood. Comprehension isgood. Sound substitutions arecommon. Repetition is poor.
    36. 36. Anomic aphasia:Injury to angular gyrusDifficulty in understanding written language andpicturesGlobal aphasia:Injury to both broca’s & wernicke’s area
    37. 37. Anomic AphasiaWhen there is a lesion damaging theangular gyrus.There is trouble understanding writtenlanguage or pictures, because visualinformation is not processed andtransmitted to Wernicke’s area.
    38. 38. Type of Aphasia andSite of LesionCharacteristic NamingErrorsNonfluent (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 whenshown a picture of a chair
    39. 39. AREA LESION FAETURESauditory associationareasword deafnessvisual associationareasword blindness called dyslexiaWernickes AphasiaGlobal Aphasiaunable to interpret the thoughtSensory AphasiaBrocas Area Causes Motor Aphasia
    40. 40. GLOBAL APHASIA(CENTRAL APHASIA)This means the combination of the expressiveproblems of Brocas aphasia and the loss ofcomprehension of Wernickes.The patient can neither speak nor understandlanguage. It is due to widespread damage to speech areasand is the commonest aphasia after a severe lefthemisphere infarct.Writing and reading are also affected.
    41. 41. Global Aphasia Damage to Broca’s area, Wernicke’s areaand the arcuate fasciculus. Abilities to speak, comprehend and repeatare impaired.
    42. 42. ANOMICNON FLUENTGLOBALAPHASIAFLUENTBROCAS AREA• WERNICK’S AREACONDUCTIONAPHASIAANGULAR GYRUSWIDESPREAD DAMAGETO SPEECH AREASEXPRESSIVE RECEPTIVE
    43. 43. 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 israpid without any meaning. Angular gyrus: Center of integration of auditory, visual, and somatestheticinformation. Damage produces aphasias. Arcuate fasciculus: To speak intelligibly, words originating in Wernicke’s area must besent to Broca’s area. Broca’s area sends fibers to the motor cortex which directly controls themusculature of speech.
    44. 44. Dyslexia:Impaired ability to readPhonemic deficitArtists, musicians, mathematiciansDysarthria:Imperfect vocalizationDefect in motor areas & their connections
    45. 45. Dyslexiawhich is a broad term applied to impaired abilityto read, due to an inherited abnormality.Causes of Dyslexia:1. Reduced ability to recall speech sounds, sothere is trouble translating them mentally intosound units (phonemes).2. There is a defect in the magnocellular portionof the visual system that slows processingand also leads to phonemic deficit.3. There is decreased blood flow in angulargyrus in categorical hemisphere in bothcases.
    46. 46. Brain Activation During Reading Reader with dyslexia shows less activation of Wernicke’s area and the angulargyrus and more activation of Broca’s area.
    47. 47. DYSARTHRIASlurred speech.Language is intactParalysis, slowing or incoordination of muscles ofarticulation or local discomfort causes various differentpatterns of dysarthria.DISORDERED ARTICULATIONExamples•gravelly speech of upper motor neurone lesions oflower cranial nerves,• jerky, ataxic speech of cerebellar lesions (ScanningSpeech),•the monotone of Parkinsons disease (Slurred),•speech in myasthenia that fatigues and dies away. Manyaphasic patients are also somewhat dysarthric.
    48. 48. nasal tract(hard) palateoral tractvelum (soft palate)velic porttonguetongue tippharynxglottis(vocal folds andspace between vocal cords)vocal folds (larynx)= vocal cordsalveolar ridgelipsteethThe Speech Production Apparatus (from Olive, p. 23)Acoustic Phonetics: Anatomy
    49. 49. Acoustic Phonetics: AnatomyTypes of phonation (from Daniloff, p. 194)quietbreathingforcedinhalationnormalphonation whisper
    50. 50. Recognition of face Right inferior temporal lobe Prosopagnosia Autonomic changes
    51. 51. An important part of the visual input goes to theinferior temporal lobe, where representations ofobjects, particularly faces, are stored.In humans, storage and recognition of faces ismore strongly represented in the right inferiortemporal lobe in right-handed individuals,though the left lobe is also active. Lesions in this area cause prosopagnosia, theinability to recognize faces. They can recognize people by their voices, andmany of them show autonomic responses whenthey see familiar as opposed to unfamiliar faces.However, they cannot identify the familiar facesthey see.
    52. 52. THANK YOU

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