Being sleep-deprived makes it difficult for our brain’s deliberate system to perform its daily miracles. A tired brain devotes less blood to the prefrontal cortex, where most of the deliberate system lives. That makes it hard for us to respond intelligently to the unexpected, think up new ideas, or stay calm under stress. Skimping on sleep also dents our ability to remember and learn anything new, because sleep is central to the brain’s ability to convert the day’s experience into long-term memories.
