Document Detail

Demonstrating the qualitative differences between semantic aphasia and semantic dementia: A novel exploration of nonverbal semantic processing.
MedLine Citation:
PMID:  22713375     Owner:  NLM     Status:  Publisher    
Semantic dementia (SD) implicates the anterior temporal lobes (ATL) as a critical substrate for semantic memory. Multi-modal semantic impairment can also be a feature of post-stroke aphasia (referred to here as "semantic aphasia" or SA) where patients show impaired regulatory control accompanied by lesions to the frontal and/or temporo-parietal cortices, and thus the two patient groups demonstrate qualitatively different patterns of semantic impairment [1]. Previous comparisons of these two patient groups have tended to focus on verbal receptive tasks. Accordingly, this study investigated nonverbal receptive abilities via a comparison of reality decision judgements in SD and SA. Pictures of objects were presented alongside non-real distracters whose features were altered to make them more/less plausible for the semantic category. The results highlighted a number of critical differences between the two groups. Compared to SD patients, SA patients: (1) were relatively unimpaired on the two alternative forced choice (2AFC) decisions despite showing a comparable degree of semantic impairment on other assessments; (2) showed minimal effects of the plausibility manipulation; (3) were strongly influenced by variations in the regulatory requirements of tasks; and (4) exhibited a reversed effect of familiarity - i.e., better performance on less commonly encountered items. These results support a distinction between semantic impairments which arise from impaired regulatory processes (e.g., SA) versus those where degraded semantic knowledge is the causal factor (e.g., SD). SA patients performed relatively well because the task structure reduced the requirement for internally generated control. In contrast, SD patients performed poorly because their degraded knowledge did not allow the fine-grained distinctions required to complete the task.
Krist A Noonan; Elizabeth Jefferies; Peter Garrard; Sheeba Eshan; Matthew A Lambon Ralph
Related Documents :
22347855 - The time course of semantic richness effects in visual word recognition.
22361165 - Enhanced early-latency electromagnetic activity in the left premotor cortex is associat...
22806665 - Learning emergent behaviours for a hierarchical bayesian framework for active robotic p...
22484205 - Morphometric gray matter differences of the medial frontal cortex influence the social ...
23873035 - Interpretation of low-vision rehabilitation outcome measures.
23406515 - Cause and prevention of moisture-induced degradation of resistance-random-access-memory...
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-2-15
Journal Detail:
Title:  Behavioural neurology     Volume:  -     ISSN:  1875-8584     ISO Abbreviation:  -     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-6-20     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8914585     Medline TA:  Behav Neurol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
School of Psychological Sciences, University of Manchester, Manchester, UK.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Previous Document:  Sylvian fissure and parietal anatomy in children with autism spectrum disorder.
Next Document:  Degenerative jargon aphasia: Unusual progression of logopenic/phonological progressive aphasia?