The Gift of Half Brained Sleep Is Not Unique to Aquatic Mammals

Matt has a special announcement this week: a new recurring type of episode called, ‘Sleep is Bloody Remarkable’. This series of episodes will share fascinating facts about sleep that will  blow your mind! In the premier episode, Matt focuses on something truly (bloody) remarkable: half-brain sleep, or unihemispheric sleep.  

Unihemispheric sleep is the phenomenon of when one hemisphere of the brain is awake, while the other sleeps. Matt goes on to discuss how the two sides of the brain rotate their sleep roles, such that after a set period of time, the side that got to undergo sleep first wakes, so that the other half of the brain gets its needed opportunity for sleep.  

Whales and dolphins are great examples of half brain sleepers. They need to maintain movement in their underwater environment. Half-brain sleep allows them to still do this while still getting plenty of NREM slumber (just one half of the brain at a time).  Birds are also capable of half-brain sleep. Birds use unihemispheric sleep for survival purposes, although for different reasons. Birds use it to keep one eye on things, literally!  

When birds land as a flock, the birds on the farthest left and right sides - the sentinels, as it were - undergo unihemispheric sleep, to keep one eye open for threat detection on their respective side (180 degree views on the left and right). The result being, combined, the entire flock gets full 360 degree panoramic threat detection. Indeed, all of the rest of the birds are allowed to sleep with both hemispheres i.e., full brain sleep.

The poor birds on the sides don’t actually get the chance to come into the middle of the flock, it seems. Instead, to get equal sleep on both sides of the brain, when one hemisphere has fulfilled its sleep need, these birds will rotate 180 degrees, and switch sides of the brain that is sleeping. Bloody remarkable! 

We humans undergo our own rendition of unihemispheric sleep…sort of =)  In an unfamiliar location, such as a hotel room, humans keep one of their hemispheres on guard in this potentially dangerous context. Meaning, one half of the brain does not go into as deep NREM sleep, almost as if it is remaining semi-conscious. Matt also notes that half-brain sleep only happens during NREM sleep. When all species go into REM sleep, both sides of the brain sleep. There is no unihemispheric dream sleep, it seems. 

Please note that Matt is not a medical doctor, and none of the content in this podcast should be considered medical advice in any way, shape, or form, nor prescriptive in any way.

The good people at Athletic Greens are the sponsors of this week’s episode, and they are generously offering three benefits for anyone who uses the above link for their first order: 1) a discount on your order; 2) a one-year free supply of vitamin D; 3) five free travel packs. Athletic Greens is a nutrition drink that combines a full complement of antioxidants, minerals and biotics, together with essential vitamins. Matt’s been using it for several years now, first because he’s serious about his health and uses it as a full nutritional insurance policy, and second, because Matt did his research on the science and ingredients in Athletic Greens and thinks it’s science and scientific data that can be taken as ground truth.

So, make your way over to Athletic Greens, and take advantage of this incredible deal. And, as always, if you have thoughts or feedback you’d like to share, please reach out to Matt on Instagram.