Short-term forgetting in senile dementia of the Alzheimer's type

Abstract

This study explored the nature of forgetting in a group of patients at the early stages of senile dementia of the Alzheimer's type (SDAT). Two experiments were conducted to test the hypothesis that abnormal forgetting in SDAT is due to a reduction in central processing resources, leading to deficits in maintenance rehearsal. The first experiment tested the patients' ability to remember consonant trigrams after an interval of 0, 5, 10 or 20 seconds, during which they were either instructed to do nothing, articulate the word “the” repeatedly, reverse pairs of digits or add pairs of digits together. The articulation distractor task caused substantial forgetting with SDAT patients in comparison with minimal forgetting in an elderly control group. They were also clearly impaired with digit reversal and digit addition as distractor tasks, although their forgetting rates were similar to the controls. The second experiment showed a substantial decrement in the SDAT patients' ability to remember consonant trigrams with both tapping and articulation as distractor tasks. Overall, these results support the hypothesis that SDAT patients have insufficent central processing resources available for maintenance rehearsal.