Dolphins Can Sleep One-half of Their Brain At a Time Say Researchers

An anonymous reader writes "Looks like the evolution in multi-core computing is something nature has already figured out. Dolphins will sleep one core while the other remains vigilant, running background tasks necessary for survival. From the article: 'The scientists wrote: "From an anthropomorphic viewpoint, the ability of the dolphin to continuously monitor its environment for days without interruption seems extreme. However, the biological, sensory and cognitive ecology of these animals is relatively unique and demanding. If dolphins sleep like terrestrial animals, they might drown. If dolphins fail to maintain vigilance, they become susceptible to predation. As a result, the apparent 'extreme' capabilities these animals possess are likely to be quite normal, unspectacular, and necessary for survival from the dolphin's perspective."'"

Evolution

[girlintraining]

The real question is: Why is sleep needed in mammals in the first place? We've already found drugs that can keep a person going without sleep for weeks or months at a time, apparently without any significant reduction in cognitive ability or any significant change in neurological functioning. It's been investigated my the military for quite some time now.

Evolution says the reason for sleep is that it improves a creature's ability to adapt... but what does sleep adapt us for? Why the downtime? Even here with mammals where never going to sleep is a survival necessity... nature kept it intact and instead segmented the brain so parts of it could sleep. Something about sleep is very, very important... but be damned if we can figure out what.

Re:Evolution

[JonySuede]

Memory consolidation [wikipedia.org] , occurs more efficiently during sleep. That alone is worth it's evolutionary cost of sleep. Sure, Nature could have stumbled upon a memory consolidation scheme that do not involved sleep but it did not and evolutionary wise it seems that having a solid long term memory is more beneficial than not having to sleep. BTW if the drugs you talk about are orexin activator/recapture inhibitor/supressing enzyme inhibitor, only one: Orextin-A, is currently without know side effects. If those drugs you talked about do not act on the orexin transmitter up regulation, please tell me about them !

So do birds.

[Black Parrot]

This is old "news". (Can we call it "olds"?)

Supposedly when you see a row of birds standing on a cable, all the ones in the middle are asleep, and the two on the end have half a brain awake so that their outside eye is paying attention.

More recent result is that even in humans, 'asleep' isn't a boolean proposition. Different parts of your brain may go to sleep at different times. Sometimes leads to "normal" sleepwalking, sometimes to horrid behavior because the impluse-suppression part is asleep and most of the rest isn't. See the overview article in a recent issue of Scientific American. (Current or previous issue, IIRC.)

Re:Evolution

[girlintraining]

That doesn't explain why Dolphins didn't just turn sleep off, since they are warm and active throughout all time. Was it just so fundamental to the brain architecture that the segmenting was needed, or is sleep providing something else that dolphins still need?

Bingo. The one question that everybody missed, because they were too busy making jokes or talking about Dolphins to realize that this evolutionary development can shed a lot of light on our own. Don't mod this up, no siree, we like our science dumbed down and sprinkled in apple sauce here! deeeerp. :(

Re:Evolution

[guttentag]

Evolution says the reason for sleep is that it improves a creature's ability to adapt... but what does sleep adapt us for?

Most creatures don't live long enough to have a need to adapt as an individual, but they adapt as a species over generations.

Humans probably have the greatest need to adapt as individuals. Every day:

• laws are changing. Today: Gay Marriage Legal! Tomorrow: Gay Marriage Illegal and Unconstitutional because the 40.46% [wikipedia.org] of the electorate said so! Next Friday: Bingo at the Supreme Court!)
• religions are changing. Today: Earth is the Center of the Universe and Stoning Pregnant Women for Sex Out of Wedlock is Good! Tomorrow: Earth Not the Center of the Universe and Abortion is Evil. Next Friday: Earth is the center of the Universe every third Thursday during certain seasons, check local listings or pastors for details.
• food sources and taboos are changing. Today: steel cans lined with BPA keep your family's food fresh! Tomorrow: BPA in bottles bad, but we're OK with BPA in cans! Next Friday: FDA outlaws all estrogen-mimicking substances including Richard Simmons.
• business and personal relationships are changing. Today: Great work, Invaluable Employee/Loving Wife! Tomorrow: You've been replaced by someone cheaper/someone cheaper! Next Friday: Special Rates at the Chapel of Love for Couples Marrying Each Other for the 3rd Time!
• even the side of the street [wikipedia.org] you may park on is changing on a regular basis.

You have to be able to adapt because society ensures that someone is constantly moving your cheese [wikipedia.org], and in return for this, you as an individual get to live longer than wild animals do.

One theory [wikipedia.org] about why we need to sleep is that we need to filter out all the crap from the stuff we need to save. During REM sleep the neurons are subjected to spontaneous, chaotic activity, strengthening memories whose neuronal substrate is already sufficiently established, and disintegrating those that are weaker. Ever built a sandcastle by the water line at the beach? The walls that are not tightly packed get washed away when the water hits them, but the ones that are tightly packed survive and seem to actually be strengthened by the encounter. In a way, that's what REM sleep may do for our memories. Without that, it's all just an unstable jumble, and you can't adapt to all the crap in your life without the clarity to know what day it is or where the heck you're supposed to be.