Neural fatigue due to intensive learning is reversed by a nap but not by quiet waking

Do brain circuits become fatigued due to intensive neural activity or plasticity? Is sleep necessary for recovery? Well-rested subjects trained extensively in a visuo-motor rotation learning task (ROT) or a visuo-motor task without rotation learning (MOT), followed by sleep or quiet wake. High-density electroencephalography showed that ROT training led to broad increases in EEG power over a frontal cluster of electrodes, with peaks in the theta (mean +/- SE: 24% +/- 6%, p = 0.0013) and beta ranges (10% +/- 3%, p = 0.01). These traces persisted in the spontaneous EEG (sEEG) between sessions (theta: 42% +/- 8%, p = 0.0001; beta: 35% +/- 7%, p = 0.002) and were accompanied by increased errors in a motor test with kinematic characteristics and neural substrates similar to ROT (81.8% +/- 0.8% vs. 68.2% +/- 2.3%; two-tailed paired t-test: p = 0.00001; Cohen's d = 1.58), as well as by score increases of subjective task-specific fatigue (4.00 +/- 0.39 vs. 5.36 +/- 0.39; p = 0.0007; Cohen's d = 0.60). Intensive practice with MOT did not affect theta sEEG or the motor test. A nap, but not quiet wake, induced a local sEEG decrease of theta power by 33% (SE: 8%, p = 0.02), renormalized test performance (70.9% +/- 2.9% vs 79.1% +/- 2.7%, p = 0.018, Cohen's d = 0.85), and improved learning ability in ROT (adaptation rate: 71.2 +/- 1.2 vs. 73.4 +/- 0.9, p = 0.024; Cohen's d = 0.60). Thus, sleep is necessary to restore plasticity-induced fatigue and performance.

Automated summary

The study found that brain circuits in well-rested subjects showed significant changes in EEG power after undergoing intensive training in a visuo-motor rotation learning task. The results suggest that sleep is necessary for restoring plasticity-induced fatigue and improving performance.