Week 8 - Semantic Memory

Question 1

Semantic Memory

Answer 1

semantic vs.. autobiographical (episodic memory)
 Semantic memory
• Knowledge about the world
• What we know

Question 2

Cognitive Neuropsychology – patients show
category specific problems

 Hillis & Caramazza (1991)

Answer 2

• Task – name line drawings
• JJ - left temporal lobe and basal ganglia damage
– animals 91% correct
– other categories 20% correct
• PS – damage left temporal lobe and smaller
damaged areas in the right temporal lobe and
frontal lobes
– animals 39% correct vegies 25% correct
– other categories 95% correct

Question 3

Category deficits = differences in

processing difficulty?

Answer 3

 Greater number patients reported with living thing
category deficit
 Possible explanation – living things less familiar and
usually more visually complex than non-living things
 Processing Difficulty Hypothesis

Question 4

Supporting evidence for this explanation:

Answer 4

 Cognitive Neuropsychology patients
 Normal participants – elderly and young participants –
living things harder even when items matched for
frequency, familiarity and prototypicality
 Not all category deficits explained like this…
• JJ – greater problem with non-living than living things
• Number other studies demonstrated differences even
after controlling for processing difficulty between living
and non-living thing items
 Some patients do show category specific deficits

Question 5

Theories of Semantic Memory

Answer 5

Neural-structure principle
Sensory/functional theory
Domain specific hypothesis
 Correlated-structure principle
Organised unitary content hypothesis
Conceptual-structural account

Question 6

Sensory/functional theory

Answer 6

 Adheres to neural-structure principle
 Information in brain segregated based on types of
information (perceptual vs. non-perceptual)
 Information about an object represented in a
distributed fashion in brain depends on modality of
input
 Allport (1985): each type of sensory information
represented in separate interconnected nodes
Nodes specific information: action-oriented
elements, kinaesthetic elements, visual elements,
tactile elements, and auditory elements

Question 7

Sensory/functional theory

 Warrington and Colleagues

Answer 7

 Sensory/functional theory assumes
1) Organisation of semantic system based on modality
specific sub-systems
─ Visual/perceptual
─ Functional/associative
2) Naming living things – visual/ perceptual information
Naming non-living things – functional/ associative
information

Question 8

Patient evidence in support of
Sensory/functional theory
 Warrington & Shallice (1984)

Answer 8

• SBY
– 75% correct non-living things
– 0% correct living things
• JBR
– 94% correct non-living things
– 4% correct living things
– JBR – problem musical instruments, gem stones,
metals, fabrics, food

Question 9

Sensory/functional theory predictions

Answer 9

• 1) recognition of all living things depends
representations in the same semantic sub-system
(visual/ perceptual) therefore….
– Specific deficits within the living things category
should not be observed
• Patients show deficit for
– fruits/vegetables relative to animals
– Animals relative to fruits/vegetables

 Warrington & Shallice - ok to have deficits outside the
living/ non-living things if these things have an
emphasis on the perceptual properties of an object
 Fruits/ vegetables emphasis on colour

Question 10

Sensory/functional theory predictions

2)

Answer 10

 2) patients with category specific deficits (living vs..
non-living) will also have deficits for the modality or
type of information tapped into via the impaired
category
Problems providing information or knowledge about
visual/perceptual characteristics or
functional/associative characteristics
 Initially patient data was consistent with the perdition
but more recent patient cases do not support this
prediction

Question 11

Sensory/functional theory predictions

 3)

Answer 11

3) patients with a deficit for visual/ perceptual or
functional/ associative knowledge should show a
categorical deficit that is most dependent on that type
of knowledge.
Living vs.. non-living things deficits.
 Patients have shown greater deficit for visual/
perceptual knowledge than functional/ associative
knowledge but they do not show any performance
differences in naming living and non-living things.

Question 12

Sensory/functional theory Argued that

Answer 12

Visual/ perceptual and functional/ associative
representations are interdependent so damage to
one would effect the other to some degree
Both living and non-living things have perceptual
and functional elements
Damage to one type of information will have some
type of impact on the other type of features

Question 13

Evidence against the Sensory/functional

theory

Answer 13

 Not well substantiated by patient data
 Damage to perceptual or non-perceptual properties 
damage categories most reliant on this type of
information
 Not always the case
– Patient EW – problem with animals BUT ok fruits,
vegies, food, musical instruments
– Patients problems processing visual information
but do not have any category specific processing
deficit

Question 14

Evidence against the Sensory/functional
theory
 Lambon-Ralph et al (1998) – patient IW

Answer 14

– Select name from 5 choices given
– IW worse given perceptual than non-perceptual
information about an object
– IW – equivalent performance for living and nonliving
things (no category deficit)
– When asked questions about items – better at
providing non-perceptual information and provided
greater amounts of non-perceptual information
about an item when asked to provide a definition
– Number patient cases no longer show the living
vs. non-living thing deficit when familiarity is
controlled

Question 15

`Evidence against the Sensory/functional

theory

Answer 15

 Normals
 Flores d’Arcais et al (1984; 1985) two studies
• Priming word pairs perceptually but not conceptually
related
• Paintbrush-carrot = priming
 Fundamentally flawed
 Pecher et al (1998) – using correct methodology – no
priming for perceptually but not conceptually related
items e.g., pizza-coin vs. pizza- hotdog

Question 16

Problems with the Sensory/functional theory

Answer 16

 Sensory/functional theory of semantics cannot
account for patients with sub-category specific
deficits
 Early supporting studies (normals and patients)
methodological problems

Question 17

Domain-specific hypothesis

Answer 17

 Assumes evolutionary pressures resulted in
specialized and functionally distinct neural circuits
that process perceptually and conceptually distinct
categories of objects
 Semantic knowledge is organised into categories
(domains) that reflect evolutionary salient distinctions
Specialised neural mechanisms for recognising
and understanding certain categories of
knowledge
Categories are those which require rapid and
efficient identification for survival and reproduction
 Animals, fruits/vegetables, conspecifics and possibly
tools important for survival.

Question 18

Evidence to support domain-specific

hypothesis

Answer 18

 Accounts for patient data sparing categories of animals,
fruits/vegies or body parts or patients with just one
category impaired
 Consistent with developmental studies:
– infants distinguish between living & non-living things
– 9 month olds – animals vs. non-animals

Question 19

Domain-specific hypothesis predictions

Answer 19

 1) Assuming distinct neural systems dedicated to
animals, fruits/vegetables, conspecifics and tools
then the other systems cannot compensate for the
damaged neural system.
Data from 16 year old patient with poorer
performance for living than non-living things had
this deficit since age 1.
More patient cases show deficits for living than
non-living things
Patients with specific-category deficits

Question 20

Domain-specific hypothesis predictions

2

Answer 20

 2) No association between a deficit for a type or
modality of knowledge and a conceptual deficit for a
specific category.
 Patients with category-specific semantic deficits
present with equivalent impairments to visual/
perceptual and functional/ associative knowledge.

Question 21

Domain-specific hypothesis predictions

3

Answer 21

3) Perceptual stages of object recognition models
might be functionally organised by domain specific
constraints and this predicts category specific visual
agnosia despite intact early visual processes
Supported by patients who have equivalent
impairments in their performance on tasks testing
visual/perceptual and functional/ associative
conceptual knowledge for living things BUT visual
agnosia for living things

Question 22

Problems with domain-specific hypothesis

Answer 22

 Lack specificity how knowledge is represented within
categories
 Selective deficits  categorical organisation but
approach does not explain how things are
represented within each category
– Plants – food or poison
– Animals – attack or food
– Tools – function, developed later

Question 23

Organised Unitary Content Hypothesis

OUCH

Answer 23

• OUCH unitary amodal semantic (conceptual)
representation system
• Members of semantic category share attributes
(humans breathe, composed certain type of
matter)
• Core semantic properties of an object tend to
be highly intercorrelated (breathing, being
composed of water, etc.)
• Category comprises highly correlated concepts
because of overlapping features

Question 24

• OUCH unitary amodal semantic (conceptual)
representation system
• Members of semantic category share attributes
(humans breathe, composed certain type of
matter)
• Core semantic properties of an object tend to
be highly intercorrelated (breathing, being
composed of water, etc.)
• Category comprises highly correlated concepts
because of overlapping features

Answer 24

 1) how concepts are represented within semantic
memory
Members of semantic category cluster close
together in feature space
Within a category representation occurs within
semantic space and is lumpy

Question 25

OUCH 2

Answer 25

Assumptions  2) Category specific patient deficits due to damage to lumpy region(s) within semantic space  Brain damage affects category members because it affects objects/concepts with similar properties and these are stored in adjacent neural areas OR Affects the highly correlated features of category members

Question 26

OUch can account for?

Answer 26

 Can account for very severe deficits  e.g., problem with animal category is a problem with the lumpy semantic space representation for animals and associated features

Question 27

Organised Unitary Content Hypothesis | (OUCH) predictions

Answer 27

• 1) OUCH predicts modality specific semantic effects • optic aphasia – cannot name an object but patient can mime the use of the object – Fits with dissociation between word access to semantics and object access to semantics and the strong link between visual attributes of an object and its use

Question 28

OUCH prediction 2

Answer 28

• 2) OUCH predicts relative sparing of categorisation performance – Patients with impaired object naming or the inability to name the attributes (features) of an object can still name the object’s superordinate category

Question 29

Organised Unitary Content Hypothesis (OUCH) predictions 3)

Answer 29

3) OUCH predicts category specific deficits – Category impairments would occur due to disruption of feature representations of items within the impaired category.

Question 30

Problems with Organised Unitary Content | Hypothesis (OUCH) predictions

Answer 30

* Type of featural representation not defined * Ways information clusters together not specified * Functional rather than neural approach

Question 31

Conceptual-Structure account

Answer 31

 Systematic relationship among properties of members of a category e.g., animals, furniture, vehicles – Bird: large, beak, wings, eats fish, flies etc. • Relationship between features of concepts which links them together into categories

Question 32

Conceptual-Structure account 2 | assumes

Answer 32

Assumes • 1) living things have more shared features than non-living things. In other words non-living things have more distinct/ informative features than living things • 2) living things – biological information is highly correlated with shared perceptual properties (can see – has eyes) AND for artefacts function information is highly correlated with distinctive perceptual properties (used for spearing – has tines) Assumes • 3) features that are highly correlated with other features will be more resistant to damage than features that are not highly correlated OR disrupting access to a given feature will disrupt access to highly correlated features

Question 33

Conceptual-Structure account prediction

Answer 33

1a) when brain damage is mild  deficit for living things when brain damage is severe  deficit for non-living things as all that is left is the highly correlated perceptual and functional features of living things

Question 34

Conceptual-Structure account prediction 1a

Answer 34

Moss et al (1998): distribution of distinctive vs. shared properties differs between living and nonliving things living things will show impairment at any level of damage, except severe since individual features of animals are more unique and therefore more likely to be damaged Artefact impairment only occurs with severe damage as the distinction between form and function is strongly correlated and therefore robust to brain damage  Category specific deficits based severity of damage

Question 35

Conceptual-Structure account prediction | 1b)

Answer 35

when brain damage is severe  deficit for living things as whole sets of intercorrelated features are wiped out when brain damage is mild  deficit for nonliving things (artefacts) as these concepts have more informative/distinct features that are wiped out at this level of damage

Question 36

Conceptual-Structure account prediction 1b evidence

Answer 36

Devlin et al (1998):  living things have a large number of intercorrelated properties and the degree of correlation between these properties is higher for living than non-living things  severe brain damage  impairment for living things as severe damage would negate shared features  mild brain damage  impairment for non-living things because mild damage impairs the distinctive features  Category specific deficits based severity of damage

Question 37

Evidence to support Conceptual-Structure | acco

Answer 37

Category specific deficits | Studies Alzheimer's patients

Question 38

Evidence to refute Conceptual-Structure | account

Answer 38

Alzheimer’s patient data – used to develop theories not replicated  Cannot explain • Selective deficit narrowly defined categories – i.e., defuse brain damage – selective category deficits such as fruits/vegies, body parts  Problem for assumption that the number and degree of intercorrelated properties relevant to all living things  Degree of severity argument • JJ and PS have similar levels of task performance (assume similar degree damage), yet show a double dissociation

Question 39

Problems with Conceptual-Structure | account

Answer 39

• Theories ok with broad category deficits but have problems accounting for fine-grained deficits • Alternative views about degree of brain damage and impairments to living vs. non-living things, views are in opposition • Theory not well supported by empirical studies and patient case

Question 40

Neuroanatomical basis of semantic memory

Answer 40

 Patients with deficits for living things damage to • Left temporal lobe • Left and right temporal lobe • Some cases right temporal lobe only • Damage to frontal and inferior parietal areas • Widespread brain damage

Question 41

Neuroanatomical basis of semantic memory |  Deficit artefacts

Answer 41

Left temporal lobe and basal ganglia • Left temporal lobe • Left frontal and inferior parietal areas

Question 42

Neuroanatomical basis of semantic memory PET

Answer 42

Living things/animals: • Inferior temporal lobe (bilateral or left hemisphere) • Bilateral occipital lobes Non-living things: • Posterior middle and inferior temporal gyri • Fusiform gyri of temporal lobes and left inferior frontal region • Lingual, parahippocampal gyri, middle occipital gyrus and dorsolateral frontal regions