11. Language Flashcards
Spoken speech
Requires acoustic analysis (use of prosody and parsing)
Written language
Recognition of visual patternSemantic paraphasia
What is the model of spoken language and cognitive system?
Spoken word → acoustic analysis → auditory input lexicon → cognitive system
Written word → orthographic analysis → Orthographic input lexicon → Cognitive system
Spoken language
Requires breaking-down speech stream and the formation of abstract representations on basis of spectral characteristics
Neuroanatomical asymmetries
- Planum temporale (Wernicke’s area)
2. Heschl’s gyrus (primary auditory cortex)
Mental lexicon
A repository of words
Semantic information
Syntactic information
Word forms (spelling, sound pattern)
Passive knowledge- 50000 words
Collins and Loftus (1975): semantic network
What is the relationship between the mental lexicon and word production?
Patients can demonstrate a number of ways in which word production goes wrong
Anomia: Lexeme level
Phonemic misorderings: bibary books
Semantic paraphasias: goat-sheep
Anomia
A form of aphasia in which the patient is unable to recall the names of everyday objects
Semantic paraphasia
A type of language output error commonly associated with aphasia, and characterised by the prediction of unintended syllables, words, or phrases during the effort to speak
Progressive semantic dementia (categorisation)
Progressive left temporal lobe damage
- initial presentation: Problems assigning object to semantic category
- Other mental and language abilities OK, including sentence comprehension and production
Category specific anomia
Living vs non-living things
What did Damasio et al. (1996) evidence about lexicon structures?
Evidence from PET → naming deficits correlate with brain regions.
How does PET do?
Highlights active brain regions only (rather than showing all brain regions)
Injection of radioisotopes (e.g. 2-deoxyglucose) at least twice during a study (control vs. experimental): differential uptake, depending on cell activity
2-DG is taken up by the cells along with glucose but cannot be metabolised
Increased metabolic activity revealed through accumulated radioactivity in cells that have been active
Brain can be mapped during different states (attention, movement, different cognitive tasks)
Technique can identify also abnormally functioning regions
How was the PET applied to visualise the brain?
Metabolic activity is measured separately in a control/comparison and an experimental condition
Difference in activity computed by subtraction methods → difference image
Difference image reveals areas most active during experimental condition: here it is the visual cortex
Difference images can be added across participants and averaged
What did Levelt (1994, 1999) believe the process from intention to speech involved?
Involves encoding into speech form from preconceived self-generated concepts
What are generating words in intention to speech?
Conceptual system
Lemma (syntactic properties and sentence structure info)
Lexeme (word form)
Agrammatism
A tendency to form sentences without the correct inflectional structure as a result of brain damage, as in Broca’s aphasia
What is involved in Gramma?
Integration and higher-order process (semantic & syntactic)
Agrammatism
ERPs
Filtered EEG activity, measured at the scalp, associated with specific cognitive processes
Filtering (signal averaging) results in ERPs (event-related potentials)
Identified by the direction and peak of the waveform (+/- amplitude) and when they occur in time (latency)
Real-time online measurement
What is a P300 result in ERPs related to?
Attention
What is a P400 result in ERPs related to?
Associated with the processing of semantic anomalies/incongruities, lexical integration.
Broca’s aphasia
Inferior prefrontal cortex affected
Primarily affects expressive language.
Effortful, telegraphic speech
Anomia
Some comprehension deficit
Some speech apraxia or dysarthria
Wericke’s aphasia
Damage to the posterior region of the superior temporal gyrus
Primarily affects receptive language
Jargon aphasia
Poor comprehension of written & spoken language; production superficially ok but meaningless
What does Wenicke’s aphasia propose?
Damage to accurate fasciculus = conduction aphasia (comprehension & spontaneous speech OK but no repetition)
According to Werkicke’s aphasia, what does damage to the left angular gyrus cause?
Agaraphia and alexia
Agraphia
Loss of writing ability
Alexia
Loss of reading ability
What is the Wernicke-Geshwind model?
Connectionist/classic localisationist model of language
Discrete language areas connected through white matter tracts
According to the Wenicke-Geshwind, responding to auditory info: information is transduced in…
- The primary auditory cortex and transmitted to…
- Wernicke’s area: representations of words accessed to determine what they are. Info is then transmitted via…
- The acuate fasciculus to…
- Broca’s area (grammar) motor plan formed to say the word. Info is then passed onto…
- The primary motor cortex for production (implements the plan, manipulates larynx etc. to produce word)
What was Hécaen and Angelergues (1964)’s study on relatively focalised lesions?
214 patients carried lesions to LH
- Small lesions to Broca’s region: rarely non-lasting effects
- Small lesions to Wernicke’s: sometimes no effect
- Medium lesions: some deficits in articulation, as likely to result from parietal or temporal lesions as around Broca’s area
- Consistent with W-G model, larger anterior lesions (across 3 lobes) more likely to give rise to articulation problems
- No specific isolable syndromes
What are the shortcomings of the W-G model?
Few pure cases (receptive and expressive problems co-exist)
22 patients with lesions in Broca’s area, only 10 had Broca’s aphasia
All patients with Broca’s (incl. autopsied and imaged) had damaged insulae
Surgical excision of classical language areas do not have permanent; stimulation of regions outside these areas produced speech disturbances
How is fMRI used to learn about language?
Improvement on MRi in terms of speed (temporal resolution)
Uses rapidly oscillating magnetic field gradients, more powerful computational techniques
Detects oxygen consumptions in active brain regions
How does fMRI detect oxygen consumption on the active brain regions?
NB: it can take up to 2 sections to first detect changes in blood flow after stimulus presentation and up to 7 sections to reach the peak.
What are the advantages of fMRI over PET?
No substances injected
One image provides structural and functional information
Better spatial resolution
Real time, repeated measurement (like ERPs)
What was Bavelier et al. (1997) study using fMRI study?
Reading silently one word at a time vs. reading consonants
Only 5-10% of illustrated areas are active
Greater activity in left hemisphere
Activated areas: Broca’s Wernicke’s area, angular gyrus
ERP study
Allows online measurements in patients who are too disabled to obtain behavioural measurements of comprehension
What did Swaab, Brown and Hagoort (1997) study using ERP?
Used N400: correlated with lexical integration (anomalies)
Compared intact persons (N=12) vs aphasic patients (N=14)
(patients: high comprehends v low comprehends)
There were three conditions: - Concordant condition - discordant - unrelated condition Normal N400 cloze procedure Auditory odd ball task (For P300)
ISI (Inter- Stimulus Interval): Long (1250ms) vs. short (100ms)
Task: listen to the sentences and the word that follows them
What were Swaab et al (1997) findings in their study using ERP?
At short ISI:
- Intact individuals: no difference between unrelated and discordant (expected differences for other comparisons)
- Aphasic patients: significant differences in N400 amplitude between all three conditions
At long ISI:
Groups look similar – no difference between unrelated and discordant
So at long ISI evidence of contextual integration
Delay in time course of low and high comprehends
What do Bilingual aphasics show?
Different patterns of recovery, including paradoxical patterns
What does translation activate?
Translation activates anterior cingulate and some bilateral structures (e.g. head of cadate nucleus)
What are some recent findings in relation to the multilingual brain?
Comparisons of early and late bilinguals and monolinguals, different proficiency, shows L2 acquisition effect: enhanced cortical thickness in left inferior frontal gyrus and thinner cortex in right IFG with later L2 acquisition
Greater anatomical white matter connectivity for early bilinguals vs monolinguals in left frontal and parietal area (10 regions) and right superior frontal gyrus, comprising 2 networks
