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

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