Working memory task performance and chunking in early Alzheimer's disease

Background Chunking is a powerful encoding strategy that significantly improves working memory performance in normal young people. Aims To investigate chunking in patients with mild Alzheimer's disease and in a control group of elderly people without cognitive impairment. Method People with mild Alzheimer's disease (0=28) were recruited and divided according to Mini-Mental State Examination score into mild and very mild disease groups. A control group of 15 elderly individuals was also recruited. All participants performed digit and spatial working memory tasks requiring either unstructured sequences or structured sequences (which encourage chunking of information) to be recalled. Results The control group and both disease groups performed significantly better on structured trials of the digit working memory tasks, indicating successful use of chunking strategies to improve verbal working memory performance. The control and very mild disease groups also performed significantly better on structured trials of the spatial task, whereas those with mild disease demonstrated no significant difference between the structured and unstructured spatial conditions. Conclusions The ability to use chunking as an encoding strategy to improve verbal working memory performance is preserved at the mild stage of Alzheimer's disease, whereas use of chunking to improve spatial working memory is impaired by this stage. Simple training in the use of chunking might be a beneficial therapeutic strategy to prolong working memory functioning in patients at the earliest stage of Alzheimer's disease.