Week 8: Concepts and their Representation in the Brain Flashcards
What is semantic knowledge?
is a category of long-term memory
Involves = Recollection of ideas, concepts, and facts (general knowledge)
What does conceptual mean?
• Something to do with the mind or mental concepts
E.g.: When you formulate an abstract philosophy to explain the world which cannot be proven or seen
So what is conceptual semantic knowledge?
We want to know how we ‘represent’ something in the mind
What are the types of mental represenation?
Analogical
Symbolic
What is analogical mental representation?
This is a mental representation that has some of the physical characterisations of an object.
E.g. A picture of a violin
A picture of a violin isn’t actually a real violin, but it has similar characterisations
Examples of analogical representations =
- Maps
- Pictures
- Diagrams
- Flow charts
What is symbolic represenatation?
This is a mental representation that allows us to think about objects or stuff in the environment.
Involves the use of =
- Signs
- Symbols
It does not correspond to the physical features of an object or idea
E.g. the word ‘violin’
Advantage of symbolic representation?
Symbolic representations are more suited to represent concepts because of their flexibility
Concept vs category
concept =
A concept has been viewed as a mental representation that picks out a category.
E.g.: Every person has a concept of a dog (mental representation) and can use that concept to pick out a category of things that one would call dogs.
Is categorisation sensitive to goals and contexts?
Yes
Are concepts used for semantic classification?
Yes
What is the classical view?
• Argue that a set of features is necessary and sufficient to be a member of a category
- Necessary = Each feature must be present
- Sufficient = If each feature is present that’s all you need
• This means that every member of a category possesses the same characteristics
- E.g.: To be a member of the category ‘bachelor’ it must possess the features: an unmarried adult male
Criticisms of classical view?
all things can sometimes be in category and has “necessary” features
- Typicality effect = Slower reaction times when making a category judgment. E.g. : for “penguin is a bird” compared to “robin is a bird” (Rips et al. 1973)
- Some members are “more members” (Rosch & Mervis, 1975)
What is the prototype model?
- Argue that concepts of something E.g. ‘bird’ are organised around similarity to a prototype
- So a robin or a sparrow can be a good prototype or a “good example” of the category bird, WHEREAS a penguin or an ostrich is a “bad example” of this category
- So when we think about a concept we think about the “best” category member
- Membership of the category is defined on = The basis of a ‘typical’ set of features
- Membership doesn’t necessarily mean the possession of all characteristics (different to the classical view)
- This model is = flexible
Criticisms of prototype model?
- Some concepts are determined by definition rather than similarity to a prototype
- Typicality is sensitive to context =
- Two objects may have the same level of typicality but one may be more suited for certain contexts compared to the others
- E.g. : Category of ‘bird’ more likely to be given to chicken if seen in a farm than a city scene
What disorders inform us about the organisation of semantic knowledge brain in the brain?
- Semantic Dementia
- Herpes Simplex Encephalitis
- Alzheimer’s disease
- Injury following stroke
What is gradual loss of semantic knowledge?
This is when concepts deteriorate gradually with some aspects of their meaning being lost before others
What is partial loss?
Partial information is a part of information lost. The knowledge is gone.
• So concepts are made up of features, and these features are gradually lost over time, NOT the whole thing!
E.g. features of a helicopter
What hemisphere supporta semantic memory?
Right and Left hemisphere
- If one hemisphere is damaged OR more severely damaged then the other hemisphere will compensate for the knowledge.
- This isn’t noticeable in speech but brain activity is reduced in the damaged area
Brain damage affects certain categories of concepts and not others, which concepts are affected?
- Problems more often with living things
- Problems with non-living things much rarer
- Living things share more features with each other than non-live things. E.g. discriminating a tiger from a cat is harder to state the differences. BUT if you distinguish a hammer from a screwdriver, they don’t share much.
- Patient will find it harder to name a tiger because they have to look at finer details, but can tell between non-living objects (but still difficulty).
What evidence supports that brain damage affects certain categories of concepts and not others?
Herpes simplex Encephalitis (HSE) =
causes lesion to the antero-medial temporal lobe.
What does patterson (
2007) want to find out?
How our brain represents semantic memory.
What are the two models patterson proposed about semantic memory?
Distributed only view: No specific hub for semantic knowledge
Distributed + hub : Specific hub for semantic knowledge
What is Distributed only view: No specific hub for semantic knowledge?
- This model argues that conceptual bits are widely distributed, are stored in sensory AND motor areas relevant to the concept.
- This is bound together via connections between the various areas.
- There is no specific region or hub that stores semantic knowledge .
- Concepts are stored in independent areas in the brain (E.g. Name is more near the Broca’s area) and they interconnect together.
- There is no single ‘core area’ responsible for semantic knowledge.
- Conclusion = There is no single area coordinating the linkages between conceptual bits
- This model predicts = If there is an impairment it will not be generalised to all the areas. E.g. remembering a cat – semantic memory of the sounds of the concept would be impaired but not the picture of the concept.
- Evidence comes from lesion studies of semantic memory disorder
What is Distributed + hub : Specific hub for semantic knowledge?
- This model is the opposite of the “distributed-only” model.
- It argues that conceptual bits are WIDELY distributed in sensory-motor areas BUT these linkages areas are coordinated by a single “hub” in the Anterior temporal lobe (red area)
- This model predicts = Lesions to the ‘hub’ will lead to semantic impairments all over. E.g. semantic knowledge about a cat will all be forgotten because everything is interconnected in one hub. Objects, sounds, pictures, words associated with that concept will be impaired!
- Evidence comes from lesion studies of semantic memory disorders
Evidence for a semantic hub: Semantic dementia:
- Semantic dementia is characterised by focal lesions in the anterior temporal lobes (Focal lesion = Focal brain lesions are a consequence of head trauma, cerebral infarcts or intracerebral hemorrhages)
- There is a loss across all semantic modalities (expect numeric representations – numbers are retained)
