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chapter 14 notes

chapter 14 notes - CHAPTER 14 Human Communication Speech...

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CHAPTER 14: Human Communication Speech production and comprehension: Most observations on the physiology of language have been made on people who have suffered strokes, or cerebrovascular accidents (brain damage caused by occlusion/rupture of blood vessel). Most important category of speech disorders is aphasia, a primary disturbance in the comprehension or production of speech. Inability to speak due to paralysis/deafness is not aphasia. Lateralization: verbal behaviour is a lateralized function; the left hemi = more important. If the left hemi is damaged/ malformed early in life, language dominance is likely to pass to the right hemi. The right hemi does still have a role: it is involved in organizing a narrative- selecting and assembling elements of what we want to say; also in the expression and recognition of emotion in tone of voice; also in prosody- normal rhythm and stress found in speech. Speech production: Conversion of perceptions, memories and thoughts into speech uses neural mechanisms of the frontal lobes. Broca’s aphasia: a form of aphasia characterized by agrammatism (troubles using function words such as a, the, some, etc), anomia (inability to name objects), and extreme difficulty in speech articulation. Speech is slow, laborious, and non-fluent. Caused by damage to Broca’s area: inferior left frontal lobe. Necessary for normal speech production. Words patients do manage to say are almost entirely content words (words conveying meaning, i.e nouns, verbs, adjectives, etc). Damage restricted to Broca’s area does not appear Broca’s aphasia; the damage must extend to surrounding regions of frontal lobe and subcortical white matter. Basal ganglia lesions (esp in caudate nucleus) can cause Broca-like aphasia. Wernicke suggested that Broca’s area contains motor memories- in particular, memories of the sequences of muscular movements needed to articulate words. People assume that Broca’s aphasics have normal comprehension but just cannot produce speech; this is incorrect. The agrammatism of the condition also disrupts patients’ ability to use grammatical info, e.g word order, to decode the meaning of a sentence. Broca’s area is crucial in learning grammatical rules, esp complex ones. Anomia is actually a primary symptom of all forms of aphasia. Broca’s aphasics recognize that their pronunciation is wrong, and try to correct it usually. Left precentral gyrus of the insula = crucial location for control of speech articulation. Apraxia of speech is centered in this area (= impaired ability to program movements of tongue, lips, and throat to produce proper sequences of speech sounds). People who often have a “tip of the tongue” phenomenon (difficulty getting just the right word out) show loss of grey matter in the left insular cortex. Broca’s area is also involved in such articulation.
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