Neuropsychology of Semantics Flashcards
Modality-specific semantics
Patient TOB had trouble with living things, but only verbally, not visually (McCarthy & Warrington, 1988)
Patient EM was much more impaired at verbal tasks than visual tasks (Warrington, 1975)
Patient AR benefitted more from cues for written words than for picture naming
Patient AC could not access visual semantic attributes, but could access other sensory attributes and non-sensory attributes (Coltheart et al., 1998)
Against Modulaity
Visual and verbal are in the same store but visual infomation is more complex (Riddoch et al., 1988) and provide Visual cues like sharp teeth can be used to answer semantic questions like “is it dangerous”
Visual impairments should be less common than verbal impairments. Don’t need to understand it is a picture of a lion.
Double dissociations
Patient A is better on visual than verbal
Patient B is better on verbal than visual
Separate areas in brain for verbal and visual information
Complexity and indirect cues cannot fully explain data
Optic aphasia
Optic aphasia (Freund, 1889; Beauvois, 1982; Coslett & Saffran, 1989)
-can recognize objects, but can’t name them from visual input
-can name object from other inputs (e.g., sound,
touch)
Category-specific deficits
Patient JBR was better at naming inanimate objects than animate objects (Warrington & Shallice, 1984)
- Problems across multiple tasks
- Some animate categories spared (body parts) and some inanimate categories damaged
Patient MD had difficulty with fruit and vegetables (Hart et al. 1985)
Patient PC had difficulty with proper names (Semenza & Zettin, 1988)
Patient BC had difficulty with medical instruments (Crosson et al. 1997)
Suggests that the brain has separate modules for many different categories
Methodological issues of category specific deficits
Controlling for frequency (Funnel & Sheridan, 1992)
- More inanimate objects than animate objects
- Inanimate objects are more frequent than animate objects in test sets
- Patients with difficulties should have more trouble with lower frequency animate items
Visual similarity of animate things
-Normal participants make more errors in distinguishing animate things than inanimate things
Prediction is that animates should be harder than inanimates in general
Evidence for category specific
Inanimate better than animate
Warrington & Shallice (1984) JBR
Animate better than inanimate (Warrington and McCarthy, 1987)
Patient YOT had difficulty with naming inanimate objects over animate objects
Patient CW had more difficulty with non-living things and body parts than living things
What is this pattern called?
Hillis and Caramazza (1991) JJ and PS showed opposite pattern to each other on same stimuli
Sensory-Functional theory
Non-living things are distinguished by their function
-Can openers open cans, telephones are used to make calls
Living things are distinguished by their perceptual properties
-Lions are yellow and have big teeth
Category-specific deficits could be due to damage in sensory or functional parts of the semantic system
Farah & McClelland (1991)
Farah & McClelland (1991)
Had students rate sensory/functional features in dictionary definitions for concepts
Living things: 7.7 perceptual / 1 functional
Non-living things: 1.4 perceptual / 1 functional
Connectionist model of naming
If you knock out functional features, this has a bigger effect n things like telephone because roughly half of the meaning rely on functioal features.
Explains why some people have different issues with naming things not because they are stored in different parts of the brain but because different kind of features in the network are damaged.
Don’t have to assume because you have a double dissociation that you have separate parts of the brain that code for living and non living thing - down to functional and visual categories
Issues for sensory/functional theory
Sensory deficits do not always appear together (Caramazza & Shelton, 1998)
KR impaired on animals, but not food
Brain imaging finds different areas
Specialized areas evolved for living/non-living distinction
