Abstract
Sleep facilitates visual perceptual learning (VPL). However, neural mechanisms underlying sleep facilitation effects remain unclear. Previously, changes in the plasticity/stability in early visual areas (EVAs), which are indexed by the amount of excitatory signals divided by that of inhibitory signals (E/I ratio), were implicated in the sleep facilitatory effects of VPL. Here, we addressed the question regarding how the medial prefrontal cortex (mPFC) and dorsolateral prefrontal cortex (DLFPC), as “control” areas, play roles in sleep facilitatory effects in VPL. Specifically, we examined how the E/I ratio changes in these prefrontal areas were correlated with offline performance gains and resistance to retrograde interference in VPL as major behavioral outcomes of sleep benefits. Subjects were trained with two different texture discrimination tasks (TDTs) before and after sleep for 90 min inside the MRI scanner. The performance of presleep TDT was measured before sleep, after sleep, and after postsleep TDT training. E/I ratios in mPFC and DLPFC were measured by magnetic resonance spectroscopy simultaneously with polysomnography during non-REM and REM sleep relative to wakefulness. Offline performance gains were defined as performance increases in presleep TDT over sleep. The retrograde interference with presleep TDT learning by postsleep TDT learning was defined as performance decreases in the presleep TDT over postsleep TDT training. During non-REM sleep, the E/I ratio increased only in DLPFC and was positively correlated with offline performance gains of the presleep TDT. During REM sleep, the E/I ratio decreased only in mPFC and was correlated with the degree of resilience to retrograde interference. As EVAs previously showed the same tendencies in DLPFC during non-REM sleep and mPFC during REM sleep, the current results suggest that DLPFC controls EVAs to have plasticity enhanced for learning during non-REM sleep, whereas mPFC is involved in controlling EVAs to have learning stabilized during REM sleep.