Theme 3: Semantic Memory Flashcards
What type of amnesia relates to impaired episodic memory?
hippocampal amnesia
what form of impairment is caused by the degeneration of the anterior temporal lobes?
semantic dementia
what is semanticisation?
when EMs changing to SMs over time
describe the hierarchical network theory of concept organisation
SM is organised into a series of hierarchical networks. Property info is stored as high up the hierarchy as possible to minimise the amount of info needing to be stored in SM. Processing takes longer when concepts are many levels apart
What are the limitations of the hierarchical network theory of concept organisation?
- Familiarity explains processing speed (not the distance between the concepts)
- Typicality effect also counters theory
- It falsely assumes that concepts belong to rigidly defined categories (they dont bc of ambiguity & vagueness)
What does the spreading activation theory state?
SM is organised on the basis of semantic relatedness. A concept is activated when brought to our attention. Activation spreads to other concepts, where closely semantically related ones are more greatly activated
What evidence supports the spreading activation theory?
- the typicality effect
- semantic priming leads to greater concept activation
is performance the fastest and most accurate at the superordinate, basic, or subordinate level?
the superordinate level
how do we know that different kinds of information about an object are stored in different brain locations?
because of patients with category-specific deficits
describe the hub-and-spoke model
Spokes: the 6 modality-specific brain areas
Hub: a general, modality-independent unified conceptual representation where we integrate knowledge of any given concept
where are hubs located according to the hub-and-spoke model?
in the anterior temporal lobes
Describe the Controlled Semantic Cognition framework proposed by Ralph et al. (2017)
Semantic cognition (SC) relies on two principal interacting neural systems:
Representation → encodes knowledge of concepts through the learning of higher-order relationships
Control → manipulates representational system activation to generate inferences and behaviours that are appropriate for each specific context
in which ways do we see that the ATL’s function is graded (Ralph et al., 2017)?
from its functionally graded cytoarchitecture, the graded partially overlapping connectivity across ATL subregions, & its graded functionality
what do we see happens moving away from the central point of the vlATL (Ralph et al., 2017)?
moving away from the central point of the vlATL weakens the cross-modal semantic function of the ATL and is more tied to a specific input modality
One could argue that the graded functionality reflects multiple mutually exclusive ATL subregions. Is this true or not, and why (Ralph et al., 2017)?
it is false because units anatomically closer to a given modality-specific spoke take part in all types of semantic processing, despite contributing somewhat more to tasks involving the proximal modality
Which area in the ATL is responsive to visual materials and concrete concepts (Ralph et al., 2017)?
the medial ATL
Which area in the ATL is responsive to social concepts (Ralph et al., 2017)?
the polar and dorsal ATL
Which area in the ATL is responsive to auditory/verbal stimuli and abstract concepts (Ralph et al., 2017)?
the anterior STS
research in various semantic impairments led to two important updates in the new connectivity-constrained version of the hub-and-spoke model. Which are these (Ralph et al., 2017)?
- semantic representations reflect collaborations between hub and spokes
- modality-specific info will be differentially important for some categories, which is analogously reflected in impairments to modality-specific regions
Semantic cognition control is implemented within a ____ neural network that interacts with (but is separate from) the ____ (Ralph et al., 2017)
distributed
semantic representation network
In their paper, Ralph et al. (2017) describe an integrative system for semantic control. What are its components and how does it work?
there are two aspects:
1. modality-specific info interacts with a transmodal hub to form generalisable concepts
2. as part of a separate executive control network, a region represents the current task context
drawing from these 2, the integrative system generates task-, time-, and context-relevant behavioural responses
What is semantic aphasia and how does it occur (Ralph et al., 2017)?
it is a deficit in manipulating and using semantic knowledge, and occurs from prefrontal or temporoparietal lesions
how does semantic aphasia prove the existence of a separate semantic control network, as described in the framework of Ralph et al. (2017)?
prefrontal regions do not encode semantic representations but are crucial for accessing, retrieving and executively manipulating semantic knowledge. Therefore, damage to those regions will cause deficits in semantic knowledge manipulation, rather than loss of semantic knowledge
Is functional specialisation graded in the control network (Ralph et al., 2017)?
there is superior–inferior functional specialisation:
inferior regions boost retrieval of weakly encoded information and superior regions contribute to more domain-general control
What did the hierarchical processing model by Quillian propose (McClelland & Rogers, 2003)?
it proposed that if concepts are organised into a hierarchy progressing from specific to general categories, then propositions true for all members of a superordinate category could be stored once at the level of the superordinate category
What is the perceptual-to-conceptual shift (McClelland & Rogers, 2003)?
A hypothesised developmental transition where infants initially categorise objects on the basis of their directly perceived visual properties, but later come to categorise them on the basis of deeper relationships
What is the premise of the parallel distributed processing (PDP) model (McClelland & Rogers, 2003)?
processing takes place via the propagation of activation among simple, neuron-like processing units
What is pattern completion in the PDP model (McClelland & Rogers, 2003)?
semantic information is reconstructed in response to probes
What is meant by McClelland and Rogers (2003) when they state that, according to their PDP model, items have internal representations?
When a network is presented with a given input, a pattern of activity arising across its hidden layer is the internal representation of that input
What aspect of semantic cognition does PDP accurately represent (McClelland & Rogers, 2003)?
its graded nature
Rumelhart built on the PDP model, emphasising its feedforward nature. How is this apparent in the model (McClelland & Rogers, 2003)?
activation flows from units representing items and relations, through hidden layers, to an output layer containing units corresponding to possible completions of three-constituent propositions