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Chapter 14.doc

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PSYC 211
Yogita Chudasama

Chapter 14: Human Communication - patient R.F. unable to read words, but able to identify which ones were mispelled - Language is an important human social behavior, that often intends to elicit a response from the other Aphasia: A category of speech disorders in which there is a disturbance in the comprehension or production of speech, cause by brain damage Speech production and comprehension: Brain Mechanisms - Knowledge of the physiology of language has bee obtained by observing the effects of brain lesions on verbal behavior - most observations being done on those who have suffered strokes or cerebrovascularaccidents(most commonly caused by the obstruction of a blood vessel, resulting in an interrupted blood flow, and cell death) Lateralization - Lateralized function: most language disturbances occur after damage to the left side of the brain - Knecht assessed the relationship between speech lateralization and handedness in people without brain damage - Found right hemisphere speech dominance in 4% or right handed people, 15% in ambidextrous, and 27% in left handed - If left hemisphere is malformed/damaged early, language dominance goes to right hemisphere - Other hemispheres play a role in speech perception since when we talk we think about memories and perceptions - The right hemisphere is involved in organizing a narrative, expression and recognition of tone of voice, and it controls prosody- normal rhythm and stress found in speech Speech production - Speaking requires several abilities: - There must be something to talk about - Happening now: Involves perceptions - what we see, hear, smell, feel - Happened in the past: Memories - Both require brain mechanisms in the posterior part of the cerebral hemispheres; occipital, temporal & parietal - We can talk about something that did not happen - through imagination we make stories as well as lies Broca’saphasia: A form of aphasia characterized by agrammatism, anomia and extreme difficulty in speech articulation. - Arises from damage to Broca’sarealocated in the inferior left frontal lobe, rostral to the base of the left primary motor cortex - People with Broca’s aphasia find it easier to say some types of words, over others - Functionwords- with grammatical meaning (ie. a, the, some, in,) are often difficult to say - Contentwords- are easier said, as they convey the meaning (ie. apple, house, throw, heavy) - People with Broca’s aphasia can understand speech better than they can produce it - - Damage restricted to cortex of Broca’s area doesn’t produce Broca’s aphasia – damage must extend to surrounding regions of frontal lobe & to underlying subcortical white matter - Lesions of basal ganglia also produce Broca’s aphasia Watkins studied 3 generations of a family – half affected by severe speech & language disorder – caused by mutation of gene found on chromosome 7 Mutations cause abnormal development of the caudate nucleus & left inferior frontal cortex, including Broca’s area - the mutation causes abnormal development of the caudate nucleus and the left inferior frontal cortex including Broca's area Wernicke - suggested Broca’s area contains motor memories – memories of the sequences of muscular movements that are needed to articulate words 3 major speech deficits in Broca's aphasics: • Agrammatism: difficulties in using grammatical constructions and comprehending; difficulties understanding verb endings or word order - Disrupts patients’ ability to use grammatical information, including world order, to decode meaning of sentence -The man swats the mosquito – would understand that there is a man, a mosquito and swatting involved but wouldn’t understand who is doing what to who Optiz & Friederici- functional-imaging studies – found that Broca’s area activated when people were taught an artificial grammar – supports understanding that region is involved in learning grammatical rules • Anomia: difficulty in finding (remembering) appropriate word to describe object, action or attribute; one of the symptoms of aphasia - Facial expression and frequent use of words like “uh” make it obvious they are trying to find the right word Difficulty with articulation – mispronouncing words, changing the sequence of sounds ie. lipstick = likstip - They realize that they are mispronouncing a word and try to fix it Dronkers- appears to have found a critical location for control of speech articulation; left precentral gyrus of the insula Insular cortex – in lateral wall of cerebral hemisphere behind anterior or temporal lobe Region normally hidden – can only be seen when temporal lobe dissected away Discovered role of region by plotting lesion of patients with and without apraxia of speech who had stroked that damaged the same area • ApraxiaofSpeech:impairment in the ability to program movements of the tongue, lips and throat required to produce the proper sequence of speech sounds (difficulty with articulation) Kuriki, Mori, Hirata & Wise – found pronunciation of words caused activation of the left anterior insula -Other studies suggest Broca’s area also involved in articulation Stewart et al. - used TMS (transcranial magnetic stimulation) to activate neurons in Broca’s area or adjacent area of primary motor cortex (Controls muscles used for speech) - Subjects said stimulation of motor cortex made them feel as though they had lost control of facial muscles - Stimulation to Broca’s area made them feel as if they were unable to get the words out Speech Comprehension -Begins with auditory system -Difference between recognizing words and understanding their meaning -Recognizing: complex perceptual task; relies on memories of sequences of sounds; occurs through neural circuit in the middle and posterior portion of the superior temporal gyrus of the left hemisphere – area is called Wernicke’s area Wernicke’s Aphasia: Description Wernicke’saphasia: form of aphasia characterized by poor speech comprehension and fluent but meaningless speech - Differs from Broca’s: fluent and unlaboured – person doesn’t strain to articulate - When they speak – seems grammatical – use “The” and “but” - Person uses few contentwords– words they string together don’t make sense - When asking if they understand something – must use nonverbal responses – very hard to understand what they are saying - They’re usually not aware of their deficit & have a have hard time understanding – perhaps why they don’t understand that what they’re saying does not make sense Wernicke’s Aphasia: Analysis - Superior temporal gyrus – region of auditory association cortex - Comprehension deficit - Because of these 2 reasons, Wernicke’s Aphasia is characterized as a receptive aphasia - Wernicke said that his area is the location of memories of the sequences of sounds that constitute words, suggests that the auditory association cortex of the superior temporal gyrus recognizes the sounds of words Recognition: Pure word deafness Pureworddeafness: Ability to hear, speak and usually read and write without being able to comprehend the meaning of speech; caused by damage to Wernicke’s area or disruption of auditory input to this region - Can recognize non-speech sounds (dog bark, doorbell) - Their own speech is excellent - Can understand what other people are saying just by reading their lips - Can read and write and at times ask people to communicate with them through writing Functional imaging studies – perception of speech sounds activates neurons in auditory association cortex of superior temporal gyrus - Most believe the left hemisphere is primarily involves in judging the timing of components of rapidly changing complex sounds - Right hemisphere is primarily involved in judging more slowly changing components, including melody - Most important aspect of sound is timing (not pitch) - 2 types of brain injury causes pure word deafness - Disruption of auditory input to Wenicke’s area - Can be caused by by bilateral damage to the primary auditory cortex - Can be caused by damage to the white matter in left temporal lobes that cuts axons bringing auditory info from primary auditory cortex to Wenicke’s area - Damage to Wernicke’s area - Brains contain circuits of mirror neurons: neurons activated either when we perform an action or see action performed by someone else - Feedback from neurons helps us understand intent of actions of others - Hearing words automatically engages brain mechanisms that control speech - Mechanisms also control mirror neurons activated by sounds of words - Feedback from subvocal articulation (very slight movements of the muscles involved in speech that don’t actually cause obvious movement) make speech easier t
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