Numerical processing and calculation deficits in Alzheimer's disease

Objectives: Despite patients with mild dementia's capacity for independent living, they still have difficulty dealing with number processing and calculation due to continued cognitive deterioration. Methods: This study used number processing and calculation tasks with number notation. The subjects of the study were comprised of two groups, an Alzheimer's disease (AD) group (N=16) and a healthy elderly group (N=16). The study compared the error rates and error types in number processing and calculation between the two groups. Results: First, the AD group showed significantly higher errors in number production, number dictation, number reading and transcoding to verbal numerals compared to the control group. The AD group presented more diverse error types in number processing. Both groups had the highest error rates in syntactic errors. Second, the AD group demonstrated remarkably higher errors than the control group in subtraction and multiplication. In addition, the AD group showed higher diversity than the control group in calculation error types. Arithmetic rule errors and factual errors were the two most frequent errors for both groups. Third, there was a double dissociation between number processing and calculation. Conclusion: This study is significant in that it dealt with a detailed analysis of number processing, specifically number transcoding to verbal numerals.