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).