0232 REM SLEEP STABILIZES VISUAL PERCEPTUAL LEARNING WHICH WAS RENDERED FRAGILE BY NREM SLEEP

Abstract

A growing body of evidence suggests that sleep spindle activity and slow-wave activity during NREM sleep play roles in enhancing visual perceptual learning (VPL). However, to successfully consolidate already enhanced VPL, a stabilization process of VPL needs to occur after the enhancement. Otherwise, VPL should be left fragile and vulnerable to interference by training of another task. That REM sleep succeeds NREM sleep during which VPL is enhanced raises the question regarding whether REM sleep plays a role in stabilization. To address this question, we tested whether VPL is still resilient to interference and therefore is stabilized if REM sleep does not occur after training. We used a two-block training paradigm using the texture discrimination task, a standard VPL task. Earlier studies have shown that learning of the first training with a stimulus is interfered by the second training with a similar but different stimulus unless the time-interval between the two trainings was longer than 60 min. Here, we separated two trainings by a 120-min interval, during which subjects either slept (sleep group, n=11) or stayed awake (control-wake group, n=10). Performance was measured before and after the first training, before the interval, and after the second training. In the control-wake group, consistently with the previous findings, the first learning was not interfered by the second, which showed stabilization of the first learning during wakefulness occurred. In the sleep group, the first learning was significantly interfered by the second training with subjects who showed only NREM sleep, whereas no such interference occurred with subjects who showed REM sleep after NREM sleep. The degree of the resilience of the first learning measured after the second training was significantly correlated with the strength of theta activity (5–7 Hz) from the visual areas retinotopically corresponding to the trained visual field during REM sleep, but not with the strength of slow-wave activity, sleep spindle activity, or the duration of slow-wave sleep during NREM sleep. These results suggest that theta activity in the visual areas during REM sleep is necessary for consolidation of VPL during sleep after training.