• Rats’ brains respond differently to the same stimulus depending on the time of day, showing weaker immediate reactions but stronger capacity for lasting memory changes during their fatigue periods
• A brain chemical called adenosine, which builds up during waking hours and makes you drowsy, appears to control this daily on-off switch for learning in the visual cortex
• Since the study used nocturnal rats and couldn’t tell whether effects came from internal body clocks or simple tiredness, applying these findings to human study schedules requires more research
• Don’t use this to plan your study time yet. Individual sleep patterns vary widely, other brain regions may work differently, and sacrificing sleep to study during a “tired window” would likely backfire

https://studyfinds.org/why-your-brain-might-learn-best-when-its-fatigued/