At the edge of semantic space: the breakdown of coherent concepts in semantic dementia is constrained by typicality and severity but not modality.

TitleAt the edge of semantic space: the breakdown of coherent concepts in semantic dementia is constrained by typicality and severity but not modality.
Publication TypeJournal Article
Year of Publication2011
AuthorsMayberry, EJ, Sage, KE, Ralph, MALambon
JournalJ Cogn Neurosci
Volume23
Issue9
Date Published2011 Sep
Abstract

Hub-and-spoke models of semantic representation suggest that coherent concepts are formed from the integration of multiple, modality-specific information sources with additional modality-invariant representations-most likely stored in the ventrolateral anterior temporal lobe (vATL). As well as providing the necessary computational mechanisms for the complexities of feature integration, these modality-invariant representations also license a key aspect of semantic memory-semantic-based generalization. Semantic dementia allows us to investigate this aspect of conceptual knowledge because (a) the patients have a selective and progressive semantic degradation and (b) this is associated with profound ventrolateral ATL atrophy. Specifically, the boundaries between concepts become degraded in semantic dementia and, when tested using the appropriate materials, the patients make simultaneous under- and overgeneralization errors. We found that the rate of these errors were a function of typicality and pseudotypicality of the items as well as the severity of the patients' semantic impairment. Following the modality-invariant nature of the vATL hub representation, we also confirmed that the patients were impaired on both verbal- and picture-based versions of the same task.

ISSN Number1530-8898
KeywordsAged, Aged, 80 and over, Analysis of Variance, Choice Behavior, Concept Formation, Female, Frontotemporal Lobar Degeneration, Humans, Male, Middle Aged, Neuropsychological Tests, Photic Stimulation, Reaction Time, Semantics, Severity of Illness Index, Temporal Lobe
URLhttp://www.ncbi.nlm.nih.gov/pubmed/21126159?dopt=Abstract
DOI10.1162/jocn.2010.21582
Alternate JournalJ Cogn Neurosci
PubMed ID21126159
Grant ListG0501632 / / Medical Research Council / United Kingdom