The effects of cognitive impairment resulting from either dementia of the Alzheimer type (DAT) or major depression (pseudodementia) on choice reaction time were examined in two conditions hypothesized to influence group performance selectively. Elderly controls had shorter reaction times than depressed patients who, in turn, were faster than dementia patients in the standard choice reaction time test. Elderly control and depressed subjects responded more quickly under conditions designed to reduce task demands. However, no effect was detected for DAT patients, presumably due to the neural constraints imposed on cognitive functioning in dementia. These results highlight the different etiologies for the intellectual decline in dementia and pseudodementia.
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