Semantic Memory Flashcards
Name 5 ways to test semantic memory
- Picture naming eg “point to…” or “what is…”
- Draw from memory
- Describe/define something, follow-up questions about it eg “how many legs does an oyster have?”
- Sort pictures according to categories
- Match items according to semantic associations
Herpes Simplex Viral Encephalitis is a viral infection that affects the ______ and ______ lobes, resulting in tissue ______. It can be bilateral or ________. As a result of damage to the hippocampus, they do have impairments in ________ memory, but also in ________ memory.
HSVE patients have ________-specific semantic deficits eg living compared to non-living things. Interestingly, they can be _______-specific (so it depends how you ask them eg: Picture of giraffe - “what is this?” (X) but asked “what is a giraffe? (tick)).
temporal frontal necrosis unilateral episodic semantic
category
modality
Organisation of semantic memory
The distributed-only view states that different ________ of things are stored in different areas of the brain. Eg: telephone - colour (vision) - ringing (sound) - pick it up (motor). So the entire ______ of this thing is distributed across a _______. The _____ can determine which part of the network is _______.
Hence, when one part is damaged, the category-specific and modality-specific impairments are caused by a loss to only ____ of the network, so _____ of the concept is lost, but it can be ______ a different way.
attributes
network
representation
network
task
accessed
part
part
accessed
Organisation of semantic memory
Name the two challenges to the distributed-only view of semantic memory
- People with HSVE often know things like bananas and grapes are a similar category, but these are vastly different things - colour, shape, how you eat it, are all different…
- People with semantic dementia also have damage in the anterior part of the temporal lobe, yet show devastating semantic impairments that cut across categories. The amount of impairment would indicate a very distributed damage across the brain, yet it is in a very restricted place.
Semantic dementia is the ______, selective loss of ________ knowledge when tested through _____ modality. It is not _______-specific, and there is a profound loss of word ______. This results in a lack of ________ and speech production (empty speech). They also have visual ______ (or inability to recognise objects). But, they have preserved _______ memory and some language aspects (eg: ______).
The damage is in the _______ and _____ temporal lobes, and is often _______ (moves from left to right)
progressive semantic any category meanings comprehension agnosia episodic syntax
anterior
lateral
asymmetric
Organisation of semantic memory
Describe the distributed-plus-hub view of semantic memory. What does this imply about categories of semantic information?
In additon to the distributed netowrk, there are also hubs of neurons in the anteriour temporal lobe that are NOT category-specific (heteromodal) or modality-specific
Neurons in these hubs direct the flow of traffic in the network, so if you remove them the entire semantic system is damaged.
This allows us to generalise across categories.
Parallel distribution processing (PDP) is a ________ model of the ______ system. You _____ the model to ______ different inputs with different outputs. Eg: a robin - can fly - is living - is a bird. There are also other ______ to this network to ensure associations ______ in the right way.
Some patterns here will be _______ with lots of overlap (eg: robin vs canary). But the bird category would show a ______ pattern of activation compared to plants.
computational semantic train associate layers flow
similar
different
Damage to the PDP network (through losing some middle layers) means the network looks more _____, and it is not possible to differentiate ______ as well (eg: different types of birds). However, you can still differentiate _______ as enough of the _______ of network activation is still there.
Damage can also occur through adding “noise” to the network. This makes the network more ______, so information maybe not _____ correctly to make the right association. Further, noise-type damage may occur in areas that are more _____, as exemplars share more features (there is more _______ for confusion). Hence, it may be more _______ to tell different birds apart compared to different cars.
sparse
features
categories
pattern
chaotic flow confusion dense opportunity difficult
Comparison of deficits in HSVE and Semantic Dementia
Despite showing damage in similar areas (anterior temporal lobe) patients with HSVE and semantic dementia show different patterns of semantic impairment (different bx patterns). Describe the Lambon, Ralph, Lowe and Rogers (2007) study which investigates this and how it relates to the PDP model.
- gave people with HSVE and semantic dementia word-picture matching tasks AND controlled for severity of semantic impairment
- SD patients showed no category-specificity whereas HSVE did have more correct in the non-living category
- Interestingly the errors made were quite different. The HSVE patients made a semantic error (called a cat a mouse) BUT the SD patients called the cat an animal when they made an error.
- so the researchers then “lesioned” the PDP model to try and recreate these patterns in correct and errors. SD patients “damage” was done by removing proportions of connections in the network (atrophy). HSVE patients damage was simulated by introducing “noise” (necrosis/disease)
- They replicated these findings in the computational model
- Conclusion was that HSVE patients easily confuse items with overlapping representations (category-specific deficits). Dense semantic neighborhoods - lots of sharing of features - noise makes things confused within categories.
- If there is a sparse network due to atrophy (SD) items are only recognised at a course level (a cat is called an animal) - gradual loss of specificity - generalisation of damage across categories. (eg: all birds fly - they resort back to that stereotype and may not remembers specifics like a penguin)
