Assessment of the semantic knowledge network in older adults with familial history of Alzheimer's disease.

摘要

Current techniques for the treatment of Alzheimer's disease rely on early implementation, which necessitates the need for accurate and early identification of individuals most at risk for future cognitive decline. Research has demonstrated the usefulness of examining the temporal gradient for long-term semantic knowledge in identification of such individuals. The assessment of the temporal gradient within varying levels of knowledge specificity, however, has received considerably less attention. In this study, we aimed to contrast accuracy and reaction times for semantic memory tasks tapping multiple dimensions of semantic specificity from multiple time epochs in adult children with and without a parental history of AD. Two supplementary aims involved: 1) examination of the integrative effects of age of memory (i.e., the temporal gradient) and specificity of information on the organization of famous person knowledge in older adults and 2) whether these effects could also be used to understand the organizational structure of conceptual word knowledge. While no group differences were observed on our novel tasks, we believe that understanding task performance at this stage is of benefit for future studies. The potential use of similar tasks in neuroimaging studies is discussed within the context of literature documenting the utility of brain activation patterns during semantic memory tasks. Finally, behavioral performance on our tasks indicates that both the age of memory and specificity of knowledge are influential in the organization of semantic networks for person knowledge. Performance on conceptual word knowledge tasks, however, does not produce a similar temporal gradient for long-term memory. We believe that this is due to the integration of episodic/autobiographical networks during recall of person knowledge. Theoretical implications of these findings for understanding the encoding and consolidation processes of long-term memory circuits and hippocampal involvement in semantic memory formation are discussed.