List length effects in item method directed forgetting in adults with and without Alzheimer's disease
MetadataShow full item record
This study seeks to explore changes in cognitive control due to normal aging as well as due to Alzheimer's disease (AD) through the item-method directed forgetting (DF) paradigm. The earliest significant manifestations of AD are deficits in patients' episodic memory as well as deficits in cognitive control - the ability to keep goal relevant information in mind despite interference. Cognitive control is thought to be paramount to an array of higher cognitive functions involved in planning and organization, as well as behavioral regulation. The DF paradigm looks specifically at intentional forgetting, whereby individuals are instructed to remember certain words and to forget others, and are then tested on both the remember items and the forget items. The DF effect refers to an increased accuracy for remember items compared to forget items, and the mechanisms of DF is thought to be closely tied to cognitive control. Greater understanding of the process of intentional forgetting may lead to discovery of strategies that can improve patient memory and potentially improve their quality of life. The DF paradigm employed in this study utilizes item-method cueing, where words to be studied are each immediately followed by the cue to remember or forget, and testing is done through a yes-no recognition task. The effect of list length - the total number of items to be studied is also examined (low, medium, high), along with an examination of source memory accuracy to words that are recognized, i.e. whether the word was a remember word or a forget word. Results comparing younger adult controls (YCs) and older adult controls (OCs) shows overall higher hit rates (percentage of correctly recognized items) across the three list lengths for YCs. Hit rate for the low condition is significantly higher compared to the medium and high list lengths. A DF effect is shown for both YCs and OCs for the low and medium conditions only, but no significant difference between the groups is present. This is contrary to the present literature, where OCs show limited to no DF effect. Source memory data shows greater accuracy for remember items compared to forget items, while performance on the task was significantly greater for YCs compared to OCs, demonstrating an age-related breakdown in source memory accuracy. A single participant with mild cognitive impairment due to AD has been tested, and the performance is shown to mirror that of OCs. Data collected thus far is still limited and more needs to be collected before further conclusions may be drawn. Greater understanding of the process of intentional forgetting may lead to discovery of strategies that can improve patient memory and potentially improve their quality of life.