A recent study looked into the brains of habitual short sleepers:
The team compared data from people who reported a normal amount of sleep in the past month with those who reported sleeping six hours or less a night. They further divided the short sleepers into two groups: Those who reported daytime dysfunction, such as feeling too drowsy to perform common tasks or keeping up enthusiasm, and those who reported feeling fine.
Both groups of short sleepers exhibited connectivity patterns more typical of sleep than wakefulness while in the MRI scanner. Anderson says that although people are instructed to stay awake while in the scanner, some short sleepers may have briefly drifted off, even those who denied dysfunction. “People are notoriously poor at knowing whether they’ve fallen asleep for a minute or two,” he says. For the short sleepers who deny dysfunction, one hypothesis is that their wake-up brain systems are perpetually in over-drive. “This leaves open the possibility that, in a boring fMRI scanner they have nothing to do to keep them awake and thus fall asleep,” says Jones. This hypothesis has public safety implications, according to Curtis. “Other boring situations, like driving an automobile at night without adequate visual or auditory stimulation, may also put short sleepers at risk of drowsiness or even falling asleep behind the wheel,” he says.
Looking specifically at differences in connectivity between brain regions, the researchers found that short sleepers who denied dysfunction showed enhanced connectivity between sensory cortices, which process external sensory information, and the hippocampus, a region associated with memory. “That’s tantalizing because it suggests that maybe one of the things the short sleepers are doing in the scanner is performing memory consolidation more efficiently than non-short sleepers,” Anderson says. In other words, some short sleepers may be able to perform sleep-like memory consolidation and brain tasks throughout the day, reducing their need for sleep at night. Or they may be falling asleep during the day under low-stimulation conditions, often without realizing it.
I’m a dysfunctional long sleeper.
I was fascinated by Tolkien’s Elves, who could sleep-on-the-go; no doubt from Tolkien’s war experience, where those who could handle sleep deprivation had an edge.
I sleep four hours a night. I can take a nap in the dentist chair, having a root canal. I can stay up doing fine detail work for two days, then sleep for maybe six hours and be back to normal.
I doubt the short sleepers who claim no dysfunction are randomly dozing off during the day. I know that is not possible in my case, as people would notice. That said, I have worked with people who cat nap during the day, but they were fully aware of it.
As far as the MRI, I’d take a nap for sure, What else is there to do? May as well put the time to good use. That’s another weird thing about some short sleepers. We can sleep whenever we like.