Early detection of Alzheimer's disease: a new working memory paradigm

Abstract

Early detection of Alzheimer's disease (AD) offers the chance to decelerate the patients' cognitive decline and to prolong a self-determined, independent life. Neuropsychological testing is one key approach to establish an early diagnosis. Whereas more global cognitive abilities can be preserved until further progression of the disease, specific executive abilities such as dual-task or active inhibition processes decline very early. Our recently developed working memory paradigm, the Block Suppression Test (BST), requires an active inhibition of irrelevant stimuli and thus should differentiate between Alzheimer patients and controls in early disease stages more accurately than classical screening instruments. In a pilot study we applied the BST, the MMSE, the clock drawing test, a digit-word transformation task as well as verbal and spatial memory span tasks to a group of 13 patients with Alzheimer's disease and 13 elderly controls and compared the instruments' capability to differentiate between patients and controls. The BST showed the highest sensitivity among all applied tests with a perfect differentiation of healthy subjects and patients. The patients' backward spans were significantly reduced, in the inhibition condition they showed disproportionally worse performances. Our results reveal a specific inhibition deficit in mild AD rather than a global working memory breakdown. The BST thus was superior for early diagnosis. However, these findings must be replicated in a larger sample to prove the BST's applicability for the early diagnostic assessment of AD and other dementias.