Broca’s Aphasia: Typical Features
- Short fragments of speech, with…
- Slowed…
- Poorly…
- Problem with…
- Speech can be…
- Comprehension can be…
- Key vocabulary is…
many pauses effortful articulated producing fluent speech with missing grammatical function words telegraphic normal intact
Wernicke’s Aphasia: Typical Features
- Speech fluent, well articulated; function words present
- BUT…
Comprehension of speech:
- Can be…
- Can’t obey…
- Cannot point to a picture for a word (e.g., horse).
Different individuals make different kinds of errors:
- Phonemic paraphasias and neologisms
- Semantic paraphasias (other word substitutions)
- Omission of content words, “empty” speech
speech may be empty or nonsensical
severely impaired
commands
e. g. expressions -> eksprehsez and kaynit
e. g. children -> boys
Classical Model of Language: Broca's area = Wernicke's area = Info is transmitted between the two via... Damage causes...
Notes:
- Broca’s area is the hub for…
- Wernicke’s area is the hub for…
- B and W areas are connected by…
- Broca’s area in the…
- Wernicke’s area at tip of…
Further suggested the bunch of fibres which run between the two centres, damage to the fibres that connected B and W aphasia, come up with a different aphasia, purposed that difficult to repeat words, because if need W area to process the auditory representations of words and need B area to pronounce the words, a task that instructs to go directly from one to the other (like repeating a word after hearing it), would disproportionately be affected if have damage to connecting fibres
production (“articulatory images” of words)
comprehension (“auditory images”)
arcuate fasciculus.
conduction aphasia, a difficulty repeating words
storing the articulatory images of words (representation of words)
storing the auditory images (representation of how words sound)
white matter fibres called arcuate fasciculus.
pre-frontal cortex, ventral lateral section on LH
posterior superior temporal lobe on LH
Problems with Classical Model
1. classical syndromes can…
- B and W areas not the only parts involved in language
- 50% of the brain is devoted to communication/language
- Not all aphasia cases…
- About 40% of aphasia cases unclassifiable on Boston assessment! - Symptoms of each…
- Broca’s aphasia:
- Wernicke’s aphasia:
Notes:
- Different symptoms for different people diagnosed with W aphasia
- Model is not capturing the dissociations to see the differences between cases
- Variation in kind of errors
arise from damage outside key areas
fit the classifications
syndrome dissociate
articulation problems vs. sentence comprehension impairment
neologisms vs. semantic paraphasias
Decomposing Language:
Current models of language identify at least five different cognitive functions that are crucial for effective language communication
Understanding speech:
- Ability to recognise…
- Ability to match…
Producing Speech:
- Ability to select…
- Ability to recall…
- Ability to…
familiar words when we hear them
words to their meanings
the right word to express a chosen meaning
the sound structure of a word to be produced
programme the articulators correctly to say the word
Hickok and Poeppel’s Dual Stream Model:
DORSAL PROCESSING STREAM:
VENTRAL PROCESSING STREAM:
Notes:
- Focuses on planning sounds, production, organising words into sentences, planning motor articular movements
- Integrated network in LH
Sound based processing
Meaning based processing - temporal area
- Recognising Auditory Words
Understanding spoken language requires specialised auditory skills
These can become selectively impaired after brain damage =
Patient MS:
- Can’t discriminate…
- Hearing is normal when…
- Test: spoke a word and patient had to point to the picture
- Unable to discriminate between two similar sounding pictures
- Able to understand language when it’s written
Other features of pure word deafness:
Auditory lexical decision: Severely impaired
Word repetition: Severely impaired
Understanding of written words: normal
Voxel Based Lesion Mapping studies:
Critical region for these skill is the…
pure word deafness (deaf to speech)
similar-sounding words:
language not involved (e.g. detecting tones)
left posterior temporal lobe (including Wernicke’s area)
- Understanding Word Meanings
A loss of knowledge of word meanings occurs in…
Some people can repeat words, but…
make semantic confusions on…
fMRI: Regions more activated for…
Activation is more…
Semantic Dementia
can’t give their meanings
word-picture matching
REAL WORDS than nonsense words
anterior than for mere speech sounds
Word production involves many of the same processes as comprehension:
need to have precise semantic knowledge of the concept we want to express
Patients with semantic dementia (anterior temporal lobe pathology) have…
trouble producing the right words (loss of general knowledge) - lack of recognition when a error is made
But production also requires unique skills:
Once we have a concept to express, current models identify these three further stages or processes
- Word Selection =
- Phonological retrieval =
- Articulatory-motor planning =
- 3 major stages involved in producing a word
- Each stage supported by a different part of the brain
Choosing the word that best fits our meaning
Retrieving knowledge of its sound form
Constructing a motor plan to articulate it
- Lexical Selection
Damage to left posterior temporal lobe can cause... Characteristics: - Speech may contain... - Can describe in detail the thing... - Sufferers very aware...
-Anomia: inability to find the names of things
Regions associated with difficulty naming pictures (implicated with anomia) despite good articulation and good knowledge retrieval =
This area predicts very poor ability…
fMRI study:
- picture naming task: region sensitive to word frequency
- rare words (harp)»_space;> common words (fish)
- parametric design
- Varied the properties of the pictures named (covertly name the picture)
- Manipulated how long the words were, how familiar the concepts were, how rare or common the actual words were
- Rare words produced more activation than common words
- Basal temporal language area – key for making that link between concepts and their labels
- Varied something continuously and looked at the areas more responsive when varied it in a way that makes it harder for that process to occur
severe word-finding difficulties
long word-finding pauses
they can’t name
of their errors
Posterior temporal lobe (mid- to inferior portion)
to name pictures
