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Speech Speech Presentation Transcript

  • PHYSIOLOGY OF SPEECH Prof. Vajira Weerasinghe Dept of Physiology
    • Peripheral function
      • phonation
      • articulation & resonance
    • Central function
      • cortical control
        • Broca’s area & Wernicke’s area
  • Phonation
      • Production of speech by the larynx
      • Speech is produced during expiration
      • during
        • breathing: vocal cords are far apart
        • phonation: vocal cords are close together, vibrated
      • pitch depends on stretch of the folds, how tightly folds are approximated
  •  
  • Phonation
      • vocal folds stretch from thyroid cartilage to arytenoid cartilage
        • vocal folds are stretched by forward rotation of thyroid crtilage & posterior rotation of arytenoid cartilage
        • loosen by thyarytenoid muscles
      • muscles controlling arytenoids open or close the glottis
      • tension of folds depends on vocalis (intrinsic) muscles & cricothyroid muscles
    video
      • electrical activity recorded from laryngeal muscles show
        • even in quiet respiration: there is some activity
        • during phonation: increased electrical activity in the adductor muscles
          • after 0.35 - 0.55 s only sounds onset
          • this time delay is necessary for pressure to build up
  • Articulation
    • modification of sounds by mouth, throat, nasal cavities, tongue, lips, jaw, soft palate
      • vowels are produced by vibration of vocal folds, air stream passes through (voiced)
      • consonants are produced by partial obstruction of air stream. Larynx may not be necessary (unvoiced)
    • resonance: cavities, sinuses
  • Articulation
    • consonants are classified according to their site of origin
      • labial (lips, teeth) p,b,w,f,m
      • dental (teeth, tongue) d,t,s,m
      • lingual (tongue, soft palate) l
      • guttural (back of tongue, soft palate) g,k
  • vagus nerve
      • internal laryngeal nerve: sensory to larynx
      • external laryngeal nerve: cricothyroid muscles
      • recurrent laryngeal nerve: all other muscles
    • frequency range of human voice
        • 40 - 2000 Hz
          • men: 122 - 163 Hz
          • women 244 - 326 Hz
  • cortical control of speech
    • speech is a mode of communication by means of sounds
      • receptive aspect
      • expressive aspect
      • psychological function
    • expressive aspect
      • production of appropriate movements of lips, tongue, palate, vocal cords, respiratory muscles
    • receptive aspect
      • auditory discrimination of these sounds
    • psychological function
      • meaning of sounds heard or uttered
  • Broca’s area
    • this is the motor (expressive) area for speech
    • it is in the frontal lobe in front of inferior end of the precentral gyrus
    • (area 44)
    • generally present in the dominant side
  • Wernicke’s area
    • this is the sensory (receptive) area for speech
    • it is in the temporal lobe in the posterior end of the superior temporal
    • generally present in the dominant side
    • comprehension of visual & auditory information
  • W B B Broca’s area W Wernicke’s area visual impulses angular gyrus auditory impulses
  • disorders of speech
    • dysphonia (aphonia)
      • difficulty in the production of speech
      • laryngeal disorder
    Video
  • disorders of speech
    • dysarthria
      • defect in articulation
        • muscle paralysis
        • upper motor or lower motor neuron lesion of the nerves concerned
        • incoordination of muscles
        • cerebellar disorders
    Video
  • disorders of speech
    • dysphasia (aphasia)
      • disorders of receptive or expressive aspect of speech
      • due to cortical abnormalities
      • different types of aphasia
  • Broca’s dysphasia (aphasia)
      • motor aphasia, expressive aphasia
      • nonfluent
      • disorder of expressive aspect of speech
      • comprehension is normal, understand written and spoken word
      • difficult to initiate speech, few disjointed words, failure to construct sentences
      • a lesion in the Broca’s area
      • spontaneous naming and repetition impaired
    Video
  • Wernicke’s dysphasia (aphasia)
      • sensory aphasia, receptive aphasia
      • fluent
      • disorder of comprehensive aspect of speech (both written and spoken word)
      • expression is normal
      • incorrect words, errors, unintelligible, structure of sentences correct but no meaning
      • jargon aphasia (rubbish)
      • a lesion in the Wernicke’s area
      • spontaneous naming and repetition impaired
    Video
  • Global aphasia
      • widespread damage
      • both receptive and expressive aspects affected
      • nonfluent
  • Conduction aphasia
      • tracts connecting Wernicke’s and Broca’s areas are damaged
      • difficulty in repetition of words, reading aloud
      • fluent
      • normal comprehension
      • abnormal meaning
      • repetition impaired
    • word blindness
      • written word is affected, normal spoken language, visual comprehension is affected
      • damage to occipital association areas
    • word deafness
      • spoken word is affected, written word is normal, auditory comprehension is affected
      • temporal lobe damage
    • dysgraphia (agraphia)
      • difficult to write, without paralysis of the hand
    • dyslexia (alexia)
      • difficulty to read
    • apraxia
      • inability to carry out a purposive movement nature of which the person understands
      • parietal lobe damage
    • agnosia
      • failure of recognition of visual, auditory or tactile objects
      • lesion in parietooccipital cortical areas
  • cerebral dominance
    • in right handers (90% of the population)
      • left side is dominant
    • in left handers (10% of the population)
      • in 60% left side is dominant
      • in 20% right side is dominant
      • in 20% bilateral
  • Cerebral asymmetry
    • Cerebral hemispheres have shown asymmetry for speech as well as for many other cognitive functions
    • Split brain operations performed in 1950-60 to prevent spread of epilepsy has given valuable information about the functional asymmetry
  • Left side
    • Mostly the dominant side
    • Verbal
    • Temporally sequential in processing
    • Mathematical leaning
  • Right side
    • Mostly the non-dominant side
    • Non-Verbal
    • Non-Mathematical non-sequential processing
    • Visuospatial tasks: reading faces, mental spatial transformations, perceiving whole from parts
    • Musical perception
  • This functional asymmetry in a structurally symmetrical structure is a unique human attribute L R