Author(s): Eugen Tarnow
Objective: Recently it was shown that free recall consists of two stages: the first few recalls empty working memory and a second stage, a reactivation stage, concludes the recall. It was also shown that the serial position curve changes in mild Alzheimer’s disease – lowered total recall and lessened primacy - are similar to second stage recall and different from recall from working memory. Here we wanted to investigate whether there were any free recall first stage changes in more advanced Alzheimer’s disease. Methods: The Tarnow Unchunkable Test (TUT) uses double integer items to separate out only the first stage, the emptying of working memory, by making it difficult to reactivate items due to the lack of intra-item relationships. Results: TUT is found to be gender and culture independent with small dependencies on age and years of education. TUT 3-item test selects out diagnosed Alzheimer’s disease but not amnestic MCI or non-amnestic MCI. On average, diagnosed Alzheimer’s disease is correlated with a loss of 0.6 memory pointers (out of an average of 2.6 pointers) and this is most pronounced for the later serial positions. Conclusion: Diagnosed Alzheimer’s disease is correlated with a loss of 0.6 working memory pointers. The identification of a lost memory pointer may have implications for improved stage definitions of Alzheimer’s disease and for remediation therapy via working memory capacity management.
