W10: Neurolinguistics, neuroimaging, language problems Flashcards
What is phrenology?
Looking at the shape of the head as though indicative of mental processes or character traits (Gall)
What does phrenology say about language?
Would suggest that language is localized to a particular brain region that would protrude when using language
Is the concept of phrenology correct?
No its not right, but the underlying idea of localization is still valid
Things like vanity, friendship and wisdom is not localised as gall proposed.
Are there any sex differences in language lateralization?
Males are more lateralised when it comes to language, being represented in just one hemisphere
Female brains are less lateralised with language - more spread out across the hemispheres
Explain language critical periods
The ability to acquire language declines with age
- language input must occur during critical period for development to proceed normally
What is evidence towards language critical periods?
Lateralisation of language
Second language acquisition (children learn better - adults struggle)
Children deprived of early language (e.g. genie didn’t learn syntax but hard to disentangle from other problems eg. neglect)
What is the subtraction method in brain imaging?
Have the participant carry out one task, then do a variant of that task
Subtract one image from another - you can then identify differences and attribute areas towards function
What are some critiques of the subtraction method?
Areas of the brain can be active without being critical
People can be dimly thinking about something else at the same time - you can’t assume they are focussing on just the one task
Neuroimaging involves what trade-off?
Temporal (what) vs. spatial (where) accuracy
Explain event-related potentials (ERP)
Place electrodes against the scalp to record the electrical activity of the brain
Present a stimulus - measure voltage changes
Is there a trade-off in ERP?
Good temporal resolution - you can tell when
But you cant tell where - poor spatial resolution
Explain ERP peaks
Labelled in terms of polarity (positive/negative) and latency (ms since stimulus)
Interestingly, a negative peak is above the line and a positive peak is below the line
Explain magnetoencephalography (MEG)
Recent method
Measures magnetic activity in the brain
Good temporal and spatial resolution (can tell when and where things happen)
Not done unless it really has to be
Why isn’t MEG used very often?
Very difficult and expensive to conduct
Need superconducting devices, extreme cooling and magnetic shielding (need shielding from magnetic activity because want to explore the tiny emissions given off by the brain)
Explain computerised axial tomography (CAT)
X-ray images are taken from all angles around the head and are integrated to form a whole picture
What are the pros to using CAT scans?
They are non-invasive, are well tolerated and are not as expensive as others
What is the temporal/spatial trade-off in a CAT scan?
Alright both temporally and spatially but not great either way
Explain positron emission tomography (PET)?
Radioactive glucose is injected into the blood
Participant given task
Detectors around the head measure where the glucose is being used
Produces a 3D model of blood flow in the brain during a task
What is the downside to PET?
It is more invasive having injections etc.
What have PET scans told us about how we process regular and irregular past tense verbs?
Different parts of the brain lit up for each - meaning we process them in different parts of the brain
Explain functional magnetic resonance imaging (fMRI)
Measures the energy released by haemoglobin in the brain areas using the most oxygen
detecting the changes in blood oxygenation and flow that occur in response to neural activity – when a brain area is more active it consumes more oxygen
What are the pros of fMRI?
Good spatial resolution, reasonable temporal resolution
More precise than PET
fMRI is not as good as….
ERP
What have fMRI’s shown us regarding sex differences in language lateralisation?
Were given nonsense word rhyme-judgement task to participants
Activation of the inferior frontal gyrus occurred in:
- The left hemisphere in men
- Both hemispheres in women
Supporting the idea that linguistic organisation differs between male and female brains
What is a major disadvantage to male brains being more lateralised?
If injured, men are more likely to be incapacitated
Explain transcranial magnetic stimulation (TMS)
Powerful magnets are used to stimulate the cortex - record physical response
Reverse of other techniques as you cause brain activity rather than observe it
Temporarily disrupts processing of the particular part of the brain to find out what tasks you need the region for
What is aphasia?
The loss of ability to speak
The study of aphasia has…
helped us to understand the organisation of language in the brain
Explain broca’s patient
He had lost the ability to speak but was intelligent and could understand language
Could only say ‘tan’ and gesture
An autopsy revealed selective damage in LHem and at junction of temporal, frontal and parietal lobes
Then went on to study 20 more cases
What is broca’s aphasia?
Speech is slow, laborious and hesitant, little inotation and articulation problems
DEFICIT IN SPEECH PRODUCTION
Explain Wernickes patient
Patient with intact speech, but very little language comprehension
An autopsy revealed selective damage in LHem rear, parietal/temporal region
What is wernickes aphasia?
Fluent but nonsensical speech, adequate syntactic structure, function words intact but problems with content words, normal prosody
DEFICIT IN SPEECH COMPREHENSION
What is more important than wernickes and brocas area separately?
The connection between them
What is pure word deafness?
Lesion disconnects wenickes area (comprehension) and heschl’s gyrus (hearing)
These patients can hear but the signals cannot get to wernickes area so they cannot understand speech
What is conduction aphasia?
Lesion damages the arcuate fasciculus - disconnects brocas and wernickes
Speech production is intact and output is well formed, they can understand most of what they hear but they’re unable to repeat what they hear
What is agrammatism?
Deficit in sentence construction
Content words are preserved better than function words
Also extends to sentence repetition and the understanding of syntactically complex sentences
What is jargon aphasia?
Syntax is intact, but major word finding problems
- Paraphasia (substituting content words for others eg pencil for pepper)
- neologisms (made up words eg swizl for whistle)
They do not realise they are doing this and get frustrated when other people cannot understand them
What is anomia?
Impairment in retrieving names of objects
Damage to the angular gyrus
Lexical-semantic anomia - can name members of some semantic category but not another
Phonological anomia: problems retrieving phonological information about word but no problem with word meaning (tip of the tongue)
What is Garrett’s model of speech production?
Conceptualisation (preverbal message)
Thinking of coffee
Formulation: concept translated into linguistic form (words, syntax, sounds)
Flat white, just one, be polite
Execution: detailed phonetic and articulatory planning, articulation = produced speech
‘a flat whit please’
What is the functional level of Garrett’s model?
- Content words are selected
- Word meanings are specified
- Words assigned to syntactic roles
What is the positional level of Garrett’s model?
- Function words are selected
- Words are put in correct order
How would you describe someone with agrammatism with Garrett’s model?
Problems translating between functional and positional levels
Can’t really get it to the positional level - can’t create a frame for the sentence, can’t get the function words you need so you can’t put the content words together in a sentence
How would you describe someone with Jargon aphasia with Garrett’s model?
Positional level is fine - affixes etc are correct even if words are wrong so you have correct syntax - words are put in right order
Problem is with functional level - finding the right words and assigning them to their role
Supporting idea that content words are retrieved independently from syntactic frames and inflections
How would you describe someone with anomia with Garrett’s model?
The two different kinds of anomia support differences in semantic and phonological processing in the functional level of Garrett’s model
