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Dorsal stream in language
dorsal region of the brain involved in speech production
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Ventral stream in language
ventral regions of the brain involved in speech comprehension
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The Hickock-Poeppel language model
- a model of brain areas involved in language comprehension and speech production
- describes dorsal pathway for production and ventral pathway for comprehension
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Aphasia
- from Greek for "lack of speech" that is not a result of deficits in sensory, intellectual, or psychiatric functioning, nor muscle weakness
- deficit arises from damage to language-specific cortical regions
- several types of aphasia exist
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Broca's Aphasia
aphasia characterized by slow, effortful speech output lacking function words, problems with grammar and articulation, in which patients rely on high-frequency, but can comprehend normally.
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Wernicke's aphasia
- aphasia characterized by fluent, meaningless speech ('word salad') with many semantic errors and little understanding (often with anosognosia)
- Patients have deficits in repetition, naming, comprehension, and have paraphasic fluency
- In severe cases, patients appear to have no concept of what language is for
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Paraphasia
- a notable feature of aphasia in which one loses the ability of speaking correctly, substitutes one word for another, and changes words and sentences in an inappropriate way
- The patient's speech is fluent but it error-prone, e.g. 'treen' instead of 'train'
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'Word salad'
apparently fluent speech, but meaningless
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Anosognosia
- a deficit of self-awareness
- a condition in which a person who suffers a certain disability seems unaware of the existence of his or her disability
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Paraphasia
a condition in which one loses the ability to speak correctly, substituting one word for another, and changing words and sentences in an inappropriate way (e.g., 'television' for 'telephone')
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Arcuate fasciculus
The neural white matter pathway connecting Broca's area and Wernicke's areas
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Conduction aphasia
aphasia due to damage to the arcuate fasciculus resulting in poor repetition and naming, but normal comprehension and fluency
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Transcortical sensory aphasia
aphasia that is similar to Wernicke's aphasia, except that patients are able to repeat language they have just heard (but still do not comprehend it)
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Transcortical motor aphasia
aphasia associated with right hemiparesis (paralysis or inability to move) that is similar to Broca's aphasia, except patients are able to repeat
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Global aphasia
- aphasia, associated with right hemiparesis, characterized by severe communication difficulties in both speech and comprehension
- Patients may have no concept of language as communication.
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Transcortical mixed aphasia
similar to global aphasia, but patients are still able to repeat
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Anomic aphasia
aphasia in which word-finding is severely impaired, usually from damage to parietal and/or temporal lobes, and patients resort to circumlocution
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Averbia
specific aphasia in which patient loses ability to use verbs
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Color anomia
specific aphasia in which patient loses ability to use color words
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Circumlocution
the use of other words to describe a specific word or idea which cannot be remembered (means ‘talking around’ something)
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Pure word deafness
inability to comprehend speech
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Amusia
The inability to recognize musical tones or to reproduce them
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Speech entrainment therapy
- patients practice mimicking audio-visual speech stimuli
- this therapy can enable them to produce fluent speech in real time.
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Subsystems of speech
- Respiration
- Phonation
- Resonance
- Articulation
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Respiration
the process of breathing
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Phonation
is the process by which the vocal folds produce certain sounds through quasi periodic vibration
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Resonance
the prolongation of sound during speech
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Articulation
the movement of the tongue, lips, jaw, and other speech organs to make speech sounds
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Dysarthria
Motor disorder affecting any or all of the 4 subsystems of speech
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Spastic dysarthria
- motor disorder caused by damage to the upper motor neurons.
- Remember that upper motor neurons originate in motor region of the cerebral cortex and carry motor information down to the lower motor neurons at a specific brain stem or spinal cord level
- Causes: Cerebral palsy, stroke, multiple sclerosis
- Symptoms: Harsh, strained voice; vocal pitch breaks; reduced speed of articulation
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Flaccid dysarthria
- motor disorder caused by damage to the lower motor neurons.
- Remember that the lower motor neurons bring the nerve impulses from the upper motor neurons out to the muscles.
- Causes: Brainstem stroke, cranial nerve palsy, myasthenia gravis (a chronic autoimmune neuromuscular disorder that is characterized by fluctuating weakness of the voluntary muscle groups)
- Symptoms: Reduced lip closure and strength of articulatory; hyper-nasality,
- breathy voice
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Speech apraxia
- a developmental or acquired problem with speech production not associated with muscle weakness.
- Its symptoms include difficulty putting sounds and syllables together in the correct order to form words.
- The condition may be developmental as in the verbal apraxia of childhood, or acquired (from disease, trauma).
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Stuttering
- a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases, and involuntary silent pauses.
- It may be caused by genetic mutations and/or head trauma. Therapy includes relaxation techniques, singing, and choral reading.
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Cluttering
- a fluency disorder in which the patient has a problem with rate, word confusion, and disorganized thoughts.
- Language is most clear at the start of utterances, but rate increases and intelligibility decreases towards the end.
- Patients are often not aware of the disorder, but can improve with therapy that focuses on attending to speech details.
- The cause is not known.
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Spoonerisms
phonemic substitution
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Malapropisms
wrong word substitution
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Freudian slips
error in speech from ‘unconscious mind’
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