Protecting episodic memory after sleep loss: Similar benefits of exercise and naps via distinct neural contributions.

Sleep loss is a public health concern requiring widely accessible cost-effective interventions to counteract the cognitive and brain health impairments caused by it. Sleep loss impairs the brain's capacity to form new episodic memories, which is critical for everyday cognition, future planning, and decision-making. In this study, we compared the protective effect of a 20-min exercise and a 90-min nap against a no-intervention control condition on the capacity to encode episodic memory after 30 h of uninterrupted wakefulness and examined underlying neural mechanisms using electroencephalography. Both exercise and nap preserved episodic memory after sleep loss, with an average of 22% higher memory performance than the control condition. Electroencephalography revealed distinct neural mechanisms within the intervention groups, which significantly contributed to memory performance. After napping, the brain-state markers of neural fatigue and sleep pressure determined memory performance more than episodic memory markers and after exercise, only episodic memory markers significantly contributed to memory performance. In contrast, in the control group, none of these markers explained memory performance. Instead, those markers were associated with fatigue, suggesting compensatory neural efforts. Consistent with the principle of neural degeneracy, in which different brain mechanisms can yield similar outcomes, after sleep loss exercise facilitates efficient neural processing while napping makes the brain state conducive to new learning. These results warrant implementation studies within safety-critical occupations such as healthcare, shiftwork, mining, and transportation, where implementing sleep hygiene recommendations to counteract sleep loss is not effective or practical, but preserving brain and cognitive health is of global importance.