L&D 1.3 - Semantic memory and the Meaning of Words

How are thoughts and concepts mapped to words?

orthographic being spelt work and phonological being how you say it

What are concepts in semantic memory?

Everything you associate with a word
eg dog has smell, movement, colour, encyclopaedic knowledge etc

what are the three cognitive theories of conceptual representations?

• collin and quinlan's hierarchically structured models
• prototype models
• embodies concepts

what are hierarchally structured models?

• Organisation based on categories
• evidence from category verification tasks such as a canary is an animal v a canary is a bird and seeing reaction time as creating these hierarchies
• however doesnt explain why it took longer for "penguin is a bird"

what are prototype models?

• noted that similarity to prototype was an essential aspect in categorising
• eg whales and penguins are not similar to prototype of mammals and birds and share features with fish so it's harder to know what category they belong to

What are embodied concepts?

• grounding concepts in body actions and perception

• eg jug has perceptual simulations (shape, size) and actions (drinking) and activates planning

• action verbs pertaining to execution-related features eg kick

• when people observe actions, similar brain regions are active as a function of the involved body part

• langauge elicits this too

What are distributed models of semantic memory in the brain?

• no single meaning centre
• concepts are distributed so theres no single meaning centre
• eg motor, motion and object in diff areas

What are the issues with embodied accounts?

• explaining abstract constructs such as truth as it's not obvious which would stimulate or what sensory-motor features would be activated

Who was patient JRB

• JRB had difficulty understanding and naming some categories

• others showed opposite pattern

• pic naming/object definiton for living and non-living

What are the differences between living and non-living properties?

• living things tend to be known for sensory-perceptual properties eg shape
• non-living things have functional properties eg actions and uses

What was damaged in JBR?

• JBR's impairments can be explained as damage to category knowledge Eg hierarchal models (living v non-living)

• selective damage of sensory features means knowledge representations are clustered (as in distributed models)

What is semantic dementia?

• herpes too affects the anterior temporal lobe (greater on left)
• leads to non-category specific semantic impairments
• inconsistent with distributed view of semantic features

what is the hierarchy in semantics?

• structure of concepts plays a role in cognitive theories
• eg living things to animal to dog to Dalmatian

How do deficits in semantic dementia appear?

• multi-modal
• impairment in recognising and understanding words/objects
• independent of how they're cued
• spoken and written affected
• not category specific or restricted to a feature type

What is relatively preserved in sd?

• grammar

• Articulation/pronounciation

• Episodic event memories

• Spatial/geographical knowledge

How is picture naming performance affected in semantic dementia?

• low frequency and specific concepts are lost first eg eagle and rooster
• specific distinctions are lost first and errors are made eg using basic level category to name a picture

How is drawing affected in semantic dementia?

• distinctions features are lost first
• patients can copy drawings
• when taken away, drawings lost distinctive features and become more generic

What other factors affect retention or loss of meanings in semantic dementia?

• familiarity/frequency
• age of acquisition
• early acquired, high frequency, typical are retained longer eg bed
• late acquired, low frequency, atypical are lost first eg camel

What results are found in categorisation experiments in sd?

• more likely to make errors with atypical members of bird category eg emu
• overgeneralisation errors eg butterfly is bird as it has wings

What is the hub and spoke model?

• temporal pole forms a modality-independent hub where features of meaning are brought together from different spoke sites

• multimodal integration in anterior temporal lobe eg touch, vision, sound etc

What does the hub and spoke model not explain about sd?

• processed involved in semantic decisions
• context-dependent language use

How are semantic processing studies conducted?

• don't only expect distributed semantic representations but also some way of selecting or deciding what's relevant for the context
• ppts perform meaning-related and conceptual tasks eg thinking of actions you perform with objects
• responses must be appropriate to task demands

How is left inferior frontal gyrus and posterior middle temporal gyrus semantic competition seen?

• competitive word generation where they had to think of possible alternatives competing with each other

• Ambiguous words being bowl v tray, bank v book

• Competition leads to more activity in lifg and p to

How is lifg activation in semantic meaning studied?

• respond to difficult word selection

• Indicate which word is more related to top one

• Comparing 2 v 4 choices elicits higher lifg activity

• Weakly related words elicit more activity than strongly related words

• Retrieving of semantic word types eg verbs over nouns and abstract over concrete concepts

What is the significance of lifg and pmts in semantic processing?

• When retrieval or semantic judgment is harder, specific brain regions not associated with sensory-motor functions is activated

• Semantic-conceptual brain processing regions are needed besides models of distribution

What is LIFG and PMTG’s role?

• LIFG for retrieving, selecting and maintaining semantic info

• Acts in concert with PMTF

• Is a converge

How are semantic processing seen in tv?

• Family fortune = select response that most people would answer
• pointless = provide a correct but more obscure polled answer

How is semantic processing done in these shows?

• brain doesnt activate all semantic associations with words or questions
• selection process to produce a winning response