Gist Distinctions in Healthy Cognitive Aging Versus Mild Alzheimer's Disease

There is limited understanding of the effects of normal and abnormal aging on gist-based memory in relation to the massive evidence regarding detail-based memory. This void is striking given the widely accepted view that memory is rarely veridical, but most often abstracted. The present study examined the effects of healthy advanced aging and mild Alzheimer's disease (AD) on three distinct forms of gist. Two of these gist forms involved a passage: transformed gist (global generalised meaning of a passage) and main-idea gist (main points of a passage). The third gist form involved a word list: categorical gist (clustering of words according to semantic categories during list recall). These gist forms were assessed in immediate and delayed recall conditions. A total of 36 participants were included: 12 cognitively healthy young seniors (65–79 years), 12 cognitively healthy old seniors (80–95 years), and 12 young seniors with mild AD (65–79 years). The findings revealed that age and dementia did not equally affect all three forms of gist. Specifically, transformed gist was relatively maintained in the cognitively healthy senior groups as compared to the other two gist forms (main-idea gist and categorical gist), whereas all three gist forms were impaired in individuals with AD. The present study suggests that transformed gist operates differently than detail-based memory in the cognitively healthy senior groups. These findings have important theoretical implications in terms of informing existing models on the interrelationship between gist and detail-based memory and clinical implications in diagnosis of AD.