• Reaction times (ms), using a computerized test [ Time Frame: one time point, at day 0 (day of inclusion) during the computerized test ] [ Designated as safety issue: No ]
  

• Apathy severity, using a specific apathy scale (Apathy Inventory) [ Time Frame: one time point, at day 0 (day of inclusion), during the visit ] [ Designated as safety issue: No ]
  

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. METHOD: Using a computerized test, each patient is asked to press a button (mouse of the computer) each time the screen of the computer becomes completely white. After pressing the button, a randomized colorized geometric figure appears on the screen, and disappears automatically after a few seconds, replaced by a new white screen.

Reaction time (in ms) between a white screen and a press of the button is analysed. After a training trial, reaction times are analysed in different experimental conditions: neutral - stimulation1 (patient gets points when pressing the button) - stress (alarm) - stimulation2 (patient gets points when pressing, after the stress trial) - extinction (similar to neutral condition).