Reward reactivates and facilitates visual perceptual learning during REM sleep

Abstract

Visual perceptual learning (VPL) is defined as a long-term performance improvement on a perceptual task as a result of perceptual experience. It has been found that sleep strengthens and consolidates VPL. In parallel to the effect of sleep, reinforcement given through external primary reward (such as water) has been found to facilitate VPL. However, it remains unclear whether sleep and reward independently influence VPL or whether they interact with each other. Our previous research has found a significant interaction between reward and sleep in performance improvement on a visual task, suggesting that the effect of reward on VPL is enhanced during sleep. Here, we investigated the neural mechanism of the interaction of reward and sleep on VPL of the texture discrimination task (TDT). Twenty-two participants were trained and tested on TDT before and after a nap during which brain activity was monitored with polysomnography. During training, half of the participants received auditory feedback and water as a reward through a tube for a correct response (reward group), while the other half only received auditory feedback for a correct response (no-reward group). First, we replicated the previous results that performance improvement after a nap was significantly larger for the reward group than for the no-reward group. Second, the reward group showed significantly longer REM sleep periods than the no-reward group. Third, during REM sleep, the reward group showed both significantly higher alpha activity at the fronto-central regions that are involved in the brain's reward system and significantly lower theta activity at the untrained side of the visual cortex, in comparison to the no-reward group. Finally, these neural modulations by reward were highly correlated with performance improvements. These results suggest that reward given during training allows the reward system to reactivate and interacts with visual processing during subsequent REM sleep.

Meeting abstract presented at VSS 2016