MATERIAL: 13 patients with Mild Cognitive Impairment (MCI), 15 patients with Alzheimer's disease (AD) and 91 elderly healthy subjects were enrolled. A computerized test using the experiment software E-prime® was designed to assess reaction times (in ms) in different experimental conditions after a training trial (neutral, stimulation, stress, stimulation after stress, extinction) and relation between the performances to the test and the Apathy Inventory (AI) scores (lack of initiative, lack of interest, emotional blunting) were observed.