Dorsal stream in language
dorsal region of the brain involved in speech production
Ventral stream in language
ventral regions of the brain involved in speech comprehension
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
- 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
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.
- 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
- 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'
apparently fluent speech, but meaningless
- 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
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')
The neural white matter pathway connecting Broca's area and Wernicke's areas
aphasia due to damage to the arcuate fasciculus resulting in poor repetition and naming, but normal comprehension and fluency
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)
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
- aphasia, associated with right hemiparesis, characterized by severe communication difficulties in both speech and comprehension
- Patients may have no concept of language as communication.
Transcortical mixed aphasia
similar to global aphasia, but patients are still able to repeat
aphasia in which word-finding is severely impaired, usually from damage to parietal and/or temporal lobes, and patients resort to circumlocution
specific aphasia in which patient loses ability to use verbs
specific aphasia in which patient loses ability to use color words
the use of other words to describe a specific word or idea which cannot be remembered (means ‘talking around’ something)
Pure word deafness
inability to comprehend speech
The inability to recognize musical tones or to reproduce them
Speech entrainment therapy
- patients practice mimicking audio-visual speech stimuli
- this therapy can enable them to produce fluent speech in real time.
Subsystems of speech
the process of breathing
is the process by which the vocal folds produce certain sounds through quasi periodic vibration
the prolongation of sound during speech
the movement of the tongue, lips, jaw, and other speech organs to make speech sounds
Motor disorder affecting any or all of the 4 subsystems of speech
- 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
- 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
- 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).
- 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.
- 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.
wrong word substitution
error in speech from ‘unconscious mind’