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Title: Automatic and executive language impairment in Alzheimer's disease
Author: Carta, Caroline
ISNI:       0000 0004 6347 1045
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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The increase in the number of people living with Alzheimer's disease (AD) and the lack of treatment available for them advocate the need to develop diagnostic tools for early and accurate diagnosis. Clinical testing offers high diagnostic accuracy during the advanced stages of the disease, but its utility decreases in detecting subtle cognitive changes during the early stage of the disease. Tests that require the use of linguistic abilities have been proven to be reliable and replicable tools in detecting dementia risk. One of the prominent early changes that can be tested through language is semantic memory (SM). The first part of the study focused on the neuropsychological debate of category specific impairment in early AD by the assessment of living and non-living categories using the category fluency test (CFT) and the second part of the study aimed to modify clinically standardised tests and devise a new one to improve the assessment of the different components of SM, executive functioning (semantic control) and automatic functioning (semantic representation). The modified tests included the CFT, which had greater demand on executive functioning than the standardised test, and confrontation naming test (CNT) which assessed both the executive and automatic functioning. Key findings suggest that semantic memory is degraded earlier on in the disease progression with a greater impairment for living categories. This impairment is highly influenced by word attributes with words higher in frequency being better preserved. Additionally, a progressive degradation of semantic knowledge is observed from the early to the late stages of AD but the pattern of living and non-living dissociation remains qualitatively similar. Results from this thesis support the view that semantic memory tests are good measures to differentiate between healthy and early AD, as semantic knowledge remains stable in healthy ageing, up until age 70. Performance between different ages in the healthy group does not differ from one group to another except for adults older than 70 years. A major finding was that the executive component of SM is earlier impaired than the automatic functioning which could possibly be that impairment threshold is reached when both the temporal and frontal areas experience neurodegeneration. Compared to the standardised test, the novel ones are more sensitive in detecting people at risk of developing the disease. These results contribute to the understanding of the memory impairment present in early AD and sets the foundation for future research regarding clinical diagnostic tools.
Supervisor: Venneri, Annalena ; Simpson, Julie Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available