The interest of the event-related desynchronization study has already been evidenced, for example in the study of the cerebral activation modifications consecutive to cognitive processes. We observed here the evolution of this index during a recognition task where the material to memorize varied. Ten young subjects had to learn and then recognize a list of words or forms. The desynchronization of the alpha rhythm consecutive to each stimulus was recorded at 14 localizations on the scalp. We observed that the time evolution of the event-related desynchronization was different in each task. In the visual task, the phenomenon began sooner and was longer lasting. As long as the cortical area were concerned, any dominance nor interhemispheric difference were observed. During the visuospatial recognition task, the event-related desynchronization was however more widespread.