26.4 - Communication: Producing and Understanding Language Flashcards
What are 3 important types of information found in language?
- Phonology = Sounds of words
- Semantics = Meaning of words
- Grammar = Combinatorial rules (syntax)
What aspect of human language can animals not learn?
They can learn individual words, but they cannot learn syntax.
What is recursion?
Embedding linguistic units within each other in a sentence.
Is language unique to humans?
Yes, but it relies on other parts of cognition (e.g. memory) that are shared with other animals.
Are there currently any animal models of language?
No
What is lexicon?
Total set of all words in a language
What is aphasia?
The inability to comprehend or formulate language because of damage to specific brain regions.
What can cause aphasia?
Stroke/ Tumour/ TBI
What are the classic aphasias?
- Broca’s aphasia (non-fluent/ productive)
- Wernicke’s aphasia (fluent/ receptive)
- Conduction aphasia
What is non-fluent aphasia and what causes it?
- Lesions of Broca’s area - deficits in speech production
- difficulty finding words/ grammar
- Features:
- Disjointed speech
- Uses mostly content words (nouns, names, etc.), not many function words
- Poor articulation, but this is not consistent between patients so it is not a motor problem
- Repetition of speech is impaired
- Patients struggle to find words or name objects
- Comprehension is spared, but have problems understanding syntax (i.e. may struggle with certain sentence structures)
- Patient is aware of deficit
Where is Broca’s area?
Left inferior frontal gyrus (Brodmann areas 44 and 45) of left cerebral hemisphere
What is fluent aphasia and what causes it?
- Lesions of Wernicke’s area - deficits in comprehension
- Features:
- Fluent speech
- Impaired comprehension
- Repetition of speech is impaired
- Normal articulation
- Grammatically correct sentences without meaning
- Patient is unaware of deficit
Where is Wernicke’s area?
Posterior part of superior temporal gyrus (Brodmann area 22) of left cerebral hemisphere
What are some types of errors that patients with Wernicke’s aphasia may make?
- Semantic paraphasia -> When an entire word is substituted for the intended word (e.g. orange instead of apple)
- Phonemic paraphasia -> When part of a word is substituted with a non-word that preserves at least half of the segments and/or number of syllables of the intended word (e.g. wife instead of knife).
- Neologisms -> Making up a word.
What aphasia is hemiplegia associated with?
[EXTRA]
- Hemiplegia is paralysis on one side of the body.
- It causes weakness, problems with muscle control, and muscle stiffness.
- It is more commonly associated with non-fluent (Broca’s) aphasia, because Broca’s area is much closer to the motor cortex, so it is more likely to be lesioned too.
Describe how limits of comprehension in a patient with non-fluent (Broca’s) aphasia. Give some experimental evidence.
- Although patients with lesions in Broca’s area generally have relatively normal comprehension, they are impaired at syntactic processing due to their problems with grammar
- Much like with their use of mostly content words in speech, they also struggle to understand grammar (e.g. some tenses) when listening
- (Caramazza & Zurif, 1976):
- Presented patients with three simple sentences like “the boy ate the apple”, “the boy kissed the girl” and “the boy was kissed by the girl”
- The patients understood the first two sentences, since they can understand the subject words and can infer the meaning from the word order and logic
- However, they struggle to understand the third sentence due to the passive voice
- The two explanations are:
- The object of the verb has moved (Trace-deletion hypothesis, Grodzinsky, 1990)
- There is a lack of working memory to process this syntax
Describe a model of the of the language systems in the brain (derived from observations of patients with aphasia).
Geschwind model (1960s) explains that when speaking a heard word:
- Auditory cortex passes auditory information to Wernicke’s cortex
- Wernicke’s cortex accesses the meaning of the word
- Wernicke’s area communicates with Broca’s area via the arcuate fasciculus
- Broca’s area stores motor information associated with that word and outputs to the motor cortex
- This leads to the speech of that word
What is the dual stream model?
*Dorsal Stream - normally left lateralised.
- network for articulation + sensory motor
- auditory-motor integration
*Ventral Stream - weakly left lateralised
- maps sound to meaning of speech
- lexical interface.
*Bilateral processing links the two streams.
How is semantic memory involved in language?
ability to connect words with their meaning.
How is WM involved in language?
*understanding speech when there is a lot of background noise
*coherence of ideas and the following through of a thought pattern
*important aspect of comprehension, especially while reading as an internalised form of language generated by visual, rather than spatial, aspects in a convergence of the cortical areas.
How is procedural memory involved in language?
enables speech with the correct phonology and grammar (pausing/ stresses)
How is priming involved in language?
one word triggers access to words with similar semantic meaning
Give some experimental evidence for the lesion that causes conduction aphasia.
[EXTRA]
(Buchsbaum, 2011):
- Mapped the areas of lesion in patients with conduction aphasia and found the most common areas of overlap
- Mapped the active areas in healthy patients performing a phonological working memory task
- The area that was most overlapping between the two groups was determined to be Area Spt (which is involved in phonological working memory)
What is conduction aphasia?
Lesion of articulate fasciculus
*Impaired speech repetition
*Otherwise normal speech production and comprehension
*also impairments in self-monitoring of speech (Lose track/ tangents)
What is primary progressive aphasia?
Neurodegeneration of the language network characterised by:
- Impaired usage, retrieval or comprehension of words (aphasia)
- Language disorder is the principal deficit (primary)
- Neurodegenerative (progressive)
Are the aphasias static?
No, there can be a mix of different aphasias after a brain injury and symptoms can change.
What are 3 variants of primary progressive aphasia?
- Progressive Non-Fluent/Agrammatic Aphasia (PNFA) -> Non-fluent
- Semantic Dementia (SD) (a.k.a. fluent) -> Fluent
- Logopenic Progressive Aphasia (LPA) -> Slow speech due to struggle to find words
Compare the symptoms of PNFA (progressive non-fluent/agrammatic aphasia) and SD (senile dementia).
(i.e. compare non-fluent vs fluent primary progressive aphasia)
What are the symptoms of the semantic variant of primary progressive aphasia?
*Progressive loss of ability to connect words to their meaning.
*Fluent speech and grammar normal
What are the symptoms of Progressive, non-fluent aphasia?
*Problems w/ word finding (anomia)/ articulation (dyspraxia)/ grammar (dysarthria)
*Halting, non-fluent speech lacking grammar
Describe the symptoms of LPA (logopenic progressive aphasia).
*Anomia (problems with word finding) –> long word-finsing pauses.
*Poor phonological STM (Struggle w/ word/ digit span tasks)
*Poor repetition (ok for short words)
*Normal articulation/ grammar.
Summarise the patterns of atrophy in different types of primary progressive aphasia. Give some experimental evidence.
(Gorno-Tempini, 2004):
- Mapped the areas of the brain that were most commnoly atrophied in NFPA, SD and LPA
- NFPA featured atrophy of the left inferior frontal and insular cortex
- SD featured atrophy of the anterior temporal lobes
- LPA featured atrophy of the posterior temporal lobe and inferior parietal lobule
Give some experimental evidence for syntax processing in different types of primary progressive aphasia.
[EXTRA?]
(Wilson, 2010):
- Tested the comprehension of different sentences in patients with NFPA and LPA
- Patients with NFPA showed the greatest inaccuracy when presented with sentences with a complex syntax (e.g. passive tense)
- Patients with LPA showed the greatest inaccuracy when presented with long sentences
- This suggests that NFPA features impairment of syntactic processing, while LPA features cognitive memory deficits
Is it just grey matter that is affected in primary progressive aphasia?
No, it can also be the white matter, especially the dorsal pathways (arcuate fasciculus) between language areas.
Summarise the main ways in which syntactic processing (i.e. understanding sentence structure) may be impaired in aphasias.
- Syntactic processing impaired in non-fluent (Broca’s) aphasia and non-fluent PPA
- Disconnection of arcuate fasciculus or damage to posterior STG (or both) impairs phonological working memory (conduction aphasia)
- Arcuate fasciculus function correlates with syntactic comprehension in PPA
Summarise the role of Broca’s area and Wernicke’s area.
- Broca’s area is involved in speech production
- Wernicke’s area is involved in language comprehension
How can you remember each of the PPA disorders?
- NFPA is essentially like Broca’s aphasia
- SD is essentially like Wernicke’s aphasia
- LPA is essentially like conduction aphasia
What is a Specific Language Impairment (SLI)?
- AKA developmental language disorder, impairment, or dysphasia.
- Identified in children when there is an unexplained and language-specific impairment compared to other children the same age.
- A subset of SLI’s may also be associated with more general (non-language) perceptual impairments, specifically a disorder of rapid auditory temporal processing and/or magnocellular visual function. Some children show improved language function after training in these perceptual skills.
- Associated with reduced structural and functional left hemisphere asymmetry in frontal language brain regions.
Who are the KE family?
- KE family in the UK (Watkins et al., 2002):
- Approx. 50% of family affected w/ language comprehension + articulation problems
- Reduced grey matter in Caudate Nucleus and increased in Putamen.
*Genotyping –> single point mutation of FOXP2 gene on chromosome 7
What is dyslexia?
[IMPORTANT]
- Dyslexia is trouble with reading despite normal intelligence
- The causes may be developmental or acquired
- Posterior parietal cortex lesions may be causes of acquired dyslexia. This is due to its role in the direction of attention, as is necessary for reading and speech in particular.
What are the different theories of language development?
*Nativism - Humans are hard-wired to acquire
language from infancy. Universal Grammar (Chomsky): a
set of constraints for organizing language.
*Behaviourism - Language is largely acquired during
development through experience.
How does language develop between 0 and 12 months?
*Auditory system reaches full maturation at 32 weeks gestation
*6 months - language specific perception of vowels
*9 months - start producing language specific speech
*12 months - language specific consonant perception
Decline in ability to perceive sounds not in native language –> why there are accents.
What are the properties of language?
Which hemisphere is commonly associated with language, how do we know?
Left
*Wada test –> common carotid on one side injected with sodium amytal which temporarily decreases activity in associated hemisphere –> deficits can be seen in language.
if LH, 50/50 between left and right hemisphere.
What is verbal dyspraxia?
difficulty placing muscles in correct place to produce speech
What is verbal dysarthria?
Weakening of muscles used to produce speech.
What are deficits seen with language in autism?
Problems w/ language and comprehension (spectrum) but don’t struggle with grammar.
What language deficits can be seen with dyslexia?
Children struggle to gain skills involved in accurate reading and spelling
Sometimes difficulty perceiving speech and chronology of sound.
What are developmental language disorders?
Language difficulties that cause problems in everyday life.
*Affecting language production and comprehension
*Language is the primary deficit
