language - semantic dementia Flashcards
Hierarchical Structured Models (Collins & Quinlan, 1969)
How are concepts organized?
Concepts are organized in a hierarchy.
General concepts are at the top (e.g., “animal”).
Specific concepts branch below (e.g., “dog,” “cat”).
What is the principle behind Cognitive Economy?
Shared features are stored at the highest level to avoid redundancy.
More specific concepts inherit features from general ones.
How is information retrieved in Hierarchical Models?
Start at the general concept and move down to specific ones.
Faster retrieval of information through inherited properties.
What do prototype models argue?
- concepts made of frequent/typical features of typical category members
- graded internal structure as a function of similarity to prototype (whales, penguins)
- can make new things you might encounter
How do prototype models explain categorization?
Prototype models focus on similarity to a prototype.
Categories are determined by how closely an item resembles the prototype.
Why is categorizing whales and penguins challenging in prototype models?
They differ significantly from typical mammals and birds.
They share features with fish, making their categorization more complex.
What problem does the hierarchical model have?
It can’t explain why verifying “A penguin is a bird” takes longer than other category verifications.
What evidence supports hierarchical models?
Evidence from category verification tasks.
Participants’ reaction times increased when moving up through more nodes in the hierarchy (e.g., “A canary is an animal” vs. “A canary is a bird”).
When people observe an action what occurs in the brain, such a running?
They will also have the leg area of the brain in the motor strip activated even if them themselves aren’t performing the action
what happens when you see the word of a concept in the brain?
The motor regions associated with this concept will also be activated - if you see someone using scissors, hands may be activated.
How do imaging studies show brain activity during action observation and performance?
Similar brain regions are active for both observing and performing actions.
Activity depends on the body part involved (e.g., mouth, hand, foot).
How does language relate to motor brain activation?
Language, especially action verbs, can activate similar motor brain regions as performing actions.
Concepts are grounded in body actions and perception.
What happens when you hear or read the word “jug”?
It activates perceptual stimulation related to the shape, size, and action associated with the object.
Actions like drinking or pouring are triggered, activating motor planning areas.
How are motor features activated during language processing?
When processing language related to actions, motor features associated with doing the action are activated.
This involves internal mental simulation of actions, similar to how mirror neurons work.
What is the overlap in brain activity when performing actions or hearing action-related words?
There is an overlap between brain regions activated when you perform an action with a body part and when you hear a word related to that body part.
Is there a single meaning centre in the brain?
No, concepts are a distributed network organized around sensory-motor functions
how are concepts organised across the brain?
there are groups of words across the brain, organises by connection
What is embodied cognition theory?
The theory that our thoughts, knowledge, and understanding are shaped by our bodily experiences.
Mind and body are connected in how we process the world.
How does embodied cognition theory explain understanding concepts?
We understand concepts through our bodily experiences, not just abstract thinking.
Our brain activates motor and sensory areas related to physical actions when thinking about certain concepts.
What is a problem with embodied cognition theories?
Abstract concepts like “TRUTH” or “BELIEVE” don’t have clear physical actions or sensory-motor features tied to them.
It’s difficult to explain how we simulate or understand these abstract concepts through bodily experiences.
What did patient JRB’s impairment reveal about categorization?
JRB had difficulty categorizing and naming living things but was good with non-living things.
He couldn’t name or define living things like a “snake” but could discuss non-living items.
How can JRB’s impairment be explained in terms of hierarchical or feature-based models?
Hierarchical models: JRB’s impairment suggests damage to category knowledge (e.g., living vs. non-living).
Distributed models: Selective damage to sensory features may have clustered representations for living vs. non-living categories.
What could explain JRB’s difficulty with living things and not non-living things?
Living things are often categorized by sensory and perceptual properties (e.g., shape).
Non-living things are categorized based on functional or action-related properties.
What brain damage could explain JRB’s impairment?
Damage to the ventral stream of the visual cortex, affecting shape and perceptual representations.
Limited ability to access sensory features for living things.
What is semantic dementia often caused by?
herpes simplex encephalitis
where is damage in SD?
- anterior temporal lobe - damage at the lobe is greater on the left than the right
- non-category specific semantic impairments
are deficits in SD specific?
no it appears to be multimodal
what is impaired in SD?
- impairment in recognition and understanding of words and objects
- Independent of whether objects are cued by smell, sound, visual shape or touch
- Spoken and written word are affected
- Not category-specific, not restricted to a feature type
what is preserved in SD?
- grammar (syntax)
- articulation (pronunciation)
- ‘episodic’ memory for events
- spatial & geographical knowledge
- executive control
- initially okay in IQ tests
what do SD patients have a loss of?
progressive loss of low level distinctive features
as the ATL has more atrophy what happens?
as you lose temporal lobe you lose more of the hierarchy - distinctive features of objects seem to be lost first.
Can SD copy drawings?
Patients can copy drawings
But if picture is then taken away, drawings lose the distinctive features of the objects and become more generic.
other factors that affect retention of loss of meanings include …
- familiarity / frequency how often objects are seen and their name are heard or read in everyday life.
- age of acquisition whether objects and their names are learned in early childhood or later childhood / adulthood.
when sd asked if a butterfly is a bird what are they likely to say?
yes - overgeneralising - has wings
theory of hub and spoke model
Theory: The temporal pole forms a modality-independent hub where features of meaning (appearance, sound, feel, use, etc.) are brought together from different spoke sites
why can people with SD not know what scissors are if their motor cortex in tact because this should activate the brain saying hand use them to cut ?
because distributive features that come together in the anterior temporal lobe to name or identify a concept cannot occur due to atrophy
what does hub and spoke model fail to explain
- Processes involved in semantic decisions
- Context-dependent language use
What is the role of the anterior temporal lobe (ATL) in the Hub and Spoke model?
The ATL is a connecting network that brings together distributed features necessary for naming or identifying concepts.
Damage to the ATL, as seen in SD, disrupts this process.
How does context influence the Hub and Spoke model in the brain?
Context determines which relevant features are activated for a concept, involving multiple brain regions.
It’s not a total distribution of features but a selective activation based on context.
How does the Hub and Spoke model explain semantic dementia (SD)?
The model explains SD by showing how damage to the ATL affects the integration of sensory features necessary for identifying concepts.
The model also captures both distributed and convergent aspects of conceptual knowledge.
