Life goes on in dreams.

15 What goes through our minds While We fall asleep? at sleep onset, students preparing for exams commonly re-experience some of the material they have been revising during the day; lovers have pervasive thoughts about their romantic partner; software developers may see bits of programming codes unfold in their mind's eye. these anecdotal observations suggest that, during the transition from wakefulness to sleep, elements from daytime activities may spontaneously re-emerge in dream-like mentation also called hypnagogic imagery. in a behavioral study published in this issue of sleep, Wamsley and colleagues 1 provide support for the existence of such spontaneous cognitive " replay " at sleep onset. in this study, healthy young participants were trained on a highly motivating visuomotor game–the downhill skiing game alpine racer ii. in this simulated skiing game, the player stands on a movable platform while holding two ski poles. the player's goal is to use his/her body to move the platform left or right to steer and thus improve the downhill skiing of an " avatar skier " presented on a computer screen. after training on the alpine racer, 30% of spontaneous mentation collected at different times during pre-sleep wakefulness and light nrem sleep (up to 300 sec after sleep onset) contained imagery (of any modality , 24%) or thoughts (6%) related to the skiing game. Wamsley et al. 1 also found that imagery directly related to training on the game (unambiguous representations of the alpine racer or of skiing) declined across time. this time-course was paralleled by a tendency for game-related incorporations to become more abstracted from the original experience. These findings do not only provide empirical evidence for spontaneous memory replay during wakefulness and light nrem sleep (stages 1 and 2), but they show that reports of subjective experience offer valuable information about cognitive processes across changing brain states. 2 consistent with animal neurophysiology data, 3 human imaging studies have demonstrated that brain activity associated with waking experiences may be reactivated during subsequent sleep, and can thus contribute to memory consolidation and improved performance. 4-7 however, although incorporation of the alpine racing game was high in the Wamsley study, suggesting abundant memory replay at sleep onset, no relationship was found between introspective measures of memory replay and later improvement in performance on the game. Whether dreaming of some tasks or stimuli may enhance subsequent memory or performance, and whether dreaming actually relates to neural …