Early detection and differential diagnosis of Alzheimer's disease and depression with neuropsychological tasks.

The development of novel treatments for Alzheimer's disease (AD), aimed at ameliorating symptoms and modifying disease processes, increases the need for early diagnosis. Neuropsychological deficits such as poor episodic memory are a consistent feature of early-in-the-course AD, but they overlap with the cognitive impairments in other disorders such as depression, making differential diagnosis difficult. Computerised and traditional tests of memory, attention and executive function were given to four subject groups: mild AD (n = 26); questionable dementia (QD; n = 43); major depression (n = 37) and healthy controls (n = 39). A visuo-spatial associative learning test accurately distinguished AD from depressed/control subjects and revealed an apparent sub-group of QD patients who performed like AD patients. QD patients' performance correlated with the degree of subsequent global cognitive decline. Elements of contextual and cued recall may account for the task's sensitivity and specificity for AD.