Binding information in short-term memory: evidence from healthy individuals, Alzheimer's Disease and other clinical populations
Rodríguez, Mario Alfredo Parra
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Memory binding is a cognitive process that enables complex objects to be stored or retrieved coherently during perception, learning, or action. Binding functions are aimed at reducing the misattribution of the features of objects in crowded and changing sensory contexts, ensuring accurate representation in visual working memory. Binding is a relatively new concept in working memory research. However, as an integrative function it provides a rich context in which to investigate the mechanisms underlying memory deterioration. In this PhD project, a range of experimental temporary binding paradigms were used to investigate whether some of the memory impairments observed in patients with Alzheimer’s Disease could be accounted for by deficits in this memory function. A set of neuropsychological tasks were used to investigate binding operations across memory domains (i.e., verbal and nonverbal), sensory modalities (i.e., visual and auditory), types of information (e.g., objects and colours), and retrieval processes (i.e., recognition and recall) in healthy individuals, Alzheimer’s Disease patients and other clinical populations. The results suggest that the efficiency of short-term memory to store bound complex events depends on the nature of the information presented (e.g., type of information bound into objects) (Chapter 2). Short-term memory seems to be equipped with relatively separate mechanisms to store integrated objects and individual features (Chapter 4). It was also observed that the binding properties of short-term memory apply to healthy young and older people, and are functions which are preserved in the elderly (Chapter 3). In two additional experimental chapters (5 and 6) the preserved binding abilities of older people were compared with temporary binding in Alzheimer’s Disease. The latter group showed a very large impairment in binding that was distinct from their impairments in memory for individual features. These findings suggest that memory binding tasks could reliably separate the cognitive changes in normal ageing from those linked with Alzheimer’ Disease. Moreover, the results of Chapter 7 suggested that memory binding tasks may detect memory changes in people that will develop Alzheimer’ Disease (i.e., asymptomatic carriers of the gene defect E280A of the Preseniline-1 gene) almost 10 years before the average age of onset. These results are relevant to our understanding of short-term memory and to the memory models currently available. Finally, it is suggested that the constructs of memory binding may increase the sensitivity of current assessment procedures for people at risk of developing Alzheimer’s Disease.