23 - Language II Flashcards
What are the issues with some of the predictions of the classical model of aphasias?
Lesion-deficit correspondence doesn’t always hold
E.g. not all patients with lesions to Broca’s present with Broca’s aphasia
Not all patients with Broca’s aphasia symptoms exhibit lesions in Broca’s area
What is a syndrome?
Constellation of symptoms
What are classical aphasia syndromes associated with?
Damage to particular vascular territories
What did the lesion overlay method reveal about where apraxia of speech is caused in the brain?
Donkers (1996) studied 25 patients with apraxia and 19 without.
All patients with apraxia had common damaged area - PRECENTRAL GYRUS OF INSULA
None of patients without had lesions there
Apraxia of speech does not appear to be caused by damage to Broca’s area proper
What is voxel-based lesion-symptom mapping?
A technique for determining regions that are responsible for specific functional impairment
For each brain voxel (0.5mm brain area) divide patients into two groups – lesion present or lesion absent in that area.
- At each voxel, perform t-test on dependent measure of language (e.g. score on language test)
Produces a map of areas significantly correlated with the language measure Better than fMRI because you know that that part of the brain plays a causal role in the impairment.
What did Dronkers (2004) reveal about brain areas associated with comprehension deficits using the VLSM procedure?
Perisylvian region important
- Middle temporal gyrus = single word comprehension and naming
- Anterior superior temporal gyrus = comprehension simple sentences
- Superior temporal sulcus and angular gyrus = short term verbal memory
- Inferior frontal areas around Broca’s = working memory for complex syntax
Broca’s area and Wernicke’s area DID NOT correlate with comprehension deficits
List the three cortical language circuits during auditory sentence comprehension?
1: Ventral route; integrating semantic information
2: Dorsal route; processing syntactical aspect of sentence
3: Dorsal route; auditory to motor mapping
Describe the first loop in auditory sentence comprehension
Primary auditory cortex -> anterior STG -> frontal cortex via ventral connections
Back projections from frontal cortex to STG and MTG via ventral route
- Supporting top-down semantic processes
Develops early around 3-5 yrs
Describe the loop that processes syntactical aspects of sentences during auditory sentence comprehension
Primary auditory cortex -> anterior STG-> frontal cortex via ventral connections.
Back projections from frontal cortex to STG/STS via dorsal route
- Support assignment of syntactical relations.
Develops late (fully mature by 11 years)
Describe the route of auditory sentence comprehension that transcribes auditory to motor mapping
Primary auditory cortex -> posterior STG -> premotor cortex via dorsal connection
- Support auditory-to-motor mapping
Operates in a bottom-up manner and already present at birth
Might subserve repetition
What is Primary Progressive aphasia?
PPA is a focal dementia presenting as an isolated and progressive language impairment.
- Other cognitive domains are well-preserved
Occurs mostly in the context of fronto-temporal lobar degeneration
3 types;
- Non-fluent/agrammatic variant
- Semantic dementia
- Logopenic variant
Describe the diagnostic features and brain abnormalities associated with non-fluent PPA
- Agrammatism in language production and/or
- Effortful, halting speech (apraxia of speech)
Additional features (2 of 3)
- Impaired comprehension of grammatically complex structures
- Spared single-word comprehension
- Spared object knowledge
Associated with predominate left posterior frontal and insula abnormalities
Describe the diagnostic features of the semantic variant of PPA
Semantic Dementia
- Impaired confrontation naming and
- Impaired single-word comprehension
Additional features (3 of 4)
- Impaired object knowledge
- Surface dyslexia (inability to read irregular words)
- Spared repetition
- Spared speech production
Describe the diagnostic features and brain abnormalities associated with logopenic PPA
- Impaired single-word retrieval in spontaneous speech and
- Impaired repetition of sentences and phrases
Additional features (3 of 4)
- Impaired object knowledge
- Surface dyslexia (inability to read irregular words)
- Spared repetition
- Spared speech production
Associated with predominant left posterior perisylvian or parietal abnormalities
