Week 7: What are the Neural Bases of Language Flashcards
Why did Broca do tests?
To see if functioning was paired or impaired
What is a Post-mortem analysis?
Used to observe brains when patient dies
What did Broca find?
There is large lesion in an area that sits in the frontal area of the brain on the left-hand side (left-hemisphere).
We NOW call this the aethereal/posterior frontal gyrus
What is a lesion?
An area of tissue that has been damaged through injury or disease
Where is language localised?
In a specific area of the left hemisphere:
- Broca’s area
- Wernicke’s area
There is more than one language area
What does localised mean?
A restrict (something) to a particular place or part of the body.
What did Wernicke do?
• Wernicke worked with patients who had = impairments in speech comprehension
If you have impairments in speech comprehension, where was this localised?
Found lesion in left temporal lobe
What did Lichtheim do?
He worked with patients who has impairments in repeating words
If you had impairments in repeating words, where was the lesion located?
lesion in the area that CONNECTS Broca’s and Wernicke’s area
What does Wernicke-Geschwind model argue?
That language networking involves multiple networking
What does Wernicke-Geschwind model say about how language networks?
- Comprehension is extracted from sounds in Wernicke’s area…
- And is passed over the arcuate fasciculus pathway…
- To Broca’s area to be translated as speech
What is Aphasia?
A language disorder caused by = damage in a specific area that control language expression and comprehension
How can aphasia be caused?
Stroke around the middle cerebral artery
- Affects ability to comprehend, repeat or produce language
How does aphasia affect primary impairments to the language system?
- Can affect speech
- Can affect reading (alexia)
- Can affect writing (agraphia)
What is a syndrome?
A set of symptoms that tend to co-occur
What is fluent aphasia?
Speech production is fluent BUT what they say makes no sense!
So there are problems in speech comprehension
Types of fluent aphasia?
- Wernicke’s Aphasia
- Conduction Aphasia
- Transcortical sensory (isolation)
What is Wernicke’s Aphasia (Fluent)?
Lesion to the temporal lobe (left-hemisphere dominance)
There are limitations of precise localisation
difficulty in auditory comprehension
- difficulty in repeating back
- Patient hears sounds but not to attach meaning to them
- They can speak but speech DOES NOT make sense
- Use of neologisms – made up words = Jargon aphasia
- Patients can be oblivious to their errors
What is auditory comprehension?
Understanding what we hear AND what we say
What is Conduction Aphasia (Fluent
Lesion to the accurate fasciculus (Pathways that connect Broca’s AND Wernicke’s areas).
- Problem with repetition
- Some problems with speech production
- Unlike some Wernicke’s aphasic patients, they can monitor their speech (aware of their errors)
- Conduit d’approche = After a few attempts, patients produce the right word
- Good comprehension
What is non-fluent aphasia?
They understand what is being said to them BUT their speech production is non-fluent
So there are problems in producing speech
Types of non-fluent aphasia?
- Broca’s Aphasia
- Global Aphasia
- Transcortical motor
What is Broca’s Aphasia (Non-Fluent)?
Often caused by a stroke
Sometimes patients have lesions that go beyond Broca’s area= (frontal lobe – part of the inferior frontal gyrus in the left-hemipshere)
What happens if you have Broca’s Aphasia (Non-Fluent)?
- Difficult to plan and organise spontaneous speech (effortful speech)
- This aphasia affects adjacent motor areas = Often associated with paralysis of the right upper limb AND buccofacial apraxia (difficulty in moving mouth and face)
- Telegraphic speech due to agrammatism
- Agrammatism = Difficulty in using syntax
- Syntax production can be impaired differently in different patients
- Patients show fewer difficulty when they are not required to spontaneously initiate speech
What is Transcortical sensory Aphasia (isolation)
(TSCA) FLUENT?
- Disorder of comprehension
- Production is filled with neologisms
- Lesions near junction of temporal, parietal and occipital lobes
What is Transcortical Motor Aphasia (TCMA)
NON-FLUENT?
- Difficulties in initiating speech
- Good comprehension
- Generally associated with dorsolateral prefrontal regions, often overlap with Broca’s area
What are the two main pathways for language?
Dorsal Pathway
Ventral Pathway
What is Dorsal pathway?
- Mostly associated with production and articulation of speech
- This is on top of the brain
What is Ventral pathway?
- Mostly associated with comprehension and semantics
- This is on bottom of the brain
- V POINTS DOWN = Bottom of brain (VENTRAL)
How does the dorsal pathway help in language?
Auditory-to-motor mapping =
The association between sounds and articulatory actions with the goal of facilitating speech output
- Important for speech repetition
- Accurate fasciculus = Key role by connecting Broca’s and Wernicke’s areas, which helps produce and understand language
How does the ventral pathway help in language?
Ventral pathway helps language by:
Mapping sound into meaning =
This is semantic processing
Semantic processing = Encoding the meaning of a word and relate it to similar words with similar meaning.
What is an event related potentional?
An event-related potential are scalp recorded voltage fluctuations that are time-locked to an event.
Types of Event-Related Potentials?
N400
LAN
P600
What is n400?
- N suggests it is negative
- 400 tells us about the latency
Latency = The time it takes for data to pass from one point on a network to another.
• N400 refers to a negativity peaking at about 400 milliseconds after stimulus onset
Stimulus onset = (the amount of time between start one on stimulus and the start of another stimulus)
Kutas & Hilyard (1980) first reported = N400 is involved in semantic processing
E.g.: “He spread the warm bread with…”
Butter
Socks
If you said socks = This a semantically unexpected word which produces a decrease in the signal of the EEG around 400ms after the word
Negativity is plotted upwards
primarily a semantic ERP NEGATIVE
What is LAN?
- LAN = Left anterior negativity
- 500ms
LAN = Involved in detecting a syntactic irregularity / syntactic violation
E.g. Violating the grammar, “She was writing a books”
- Syntactic violations produce a decrease in the EEG signal around 300-500ms after stimulus onset
- Depending on the violation the ms can vary
primarily a syntactic ERP NEGATIVE
What is P600?
- P suggests it is positive
- 600-800ms
- P600 is associated with the processing of grammatical anomalies
- This is a syntactic component
- Studies have found it outside of language (E.g. Patel et al (1998) in music; Lelekov et al (2000) in maths)
- Violations produces an increase in the EEG signal 600-800ms after stimulus onset (positive is downward)
primarily a syntactic ERP POSITIVE
Can the brain respond specifically to language stimuli from birth?
newborns can differentiate speech AND non-speech
Newborns showed an increase activation in the left-hemisphere
Pena et al. (2003) study
What did Gervain use to detect brain activation for repeated syllables?
NIRS (near-infrared spectroscopy)
Can newborn brains detect certain irregularities in language input?
Yes
Gervain found this!
What area of the brain responds to adjacent syllables?
Left temporal and frontal areas responded more to adjacent syllables E.g.: “mubaba” “penana”
What age can babies associate novel words to objects?
3 months
They dont remember the association the next day
Friedrich & Friederici (2015)
What can babies do by the end of the first year?
Babies can discriminate familiar AND unfamiliar words
Thierry et al., (2003); Mils et al., 2004 study
What does the developmental disorder do?
Affects the domain of language processing, with unaffected intelligence, affective processes and auditory abilities
• Friederici (2004) said = Children at (genetic) risk show decreased responses in what?
- Phonological processing
- Semantic (depicted) processing
- Syntactic processing
