How Your Brain Fights Sleep Even When You're Exhausted

iStock
iStock

Maybe you’ve got an exam in the morning, or there’s just one more episode left in this season. Whatever the reason, tonight you ignore your body’s demands and stay up instead. It’s an impressive feat, if you think about it—sleep is essential—and now scientists may be closer to understanding how we do it. They published a report on their findings in the journal Neuron.

There’s a little section of your brainstem called the dorsal raphe nucleus (DRN). This region is responsible for making serotonin and other brain chemicals.

Lead researcher Viviana Gradinaru of Caltech says previous studies have also suggested that the dorsal raphe nucleus plays a role in helping keep us awake.

"People who have damage in this part of their brain have been shown to experience excessive daytime sleepiness,” she said in a statement, “but there was not a good understanding of the exact role of these neurons in the sleep/wake cycle and whether they react to internal or external stimuli to influence arousal."

Within the dorsal raphe nucleus lies a little-understood group of dopamine cells called the dorsal raphe nucleus neurons (DRNDA).

Color image of dorsal raphe nucleus neurons
Dorsal raphe nucleus neurons responding to light (green) and chemical (red) signals.
Viviana Gradinaru

Gradinaru and her colleagues wanted to know if voluntary wakefulness had anything to do with dopamine activity within these cells. They started by studying mouse brains, which are similar to our own in many ways.

The researchers monitored the rodents’ DRNDA action while the mice were fed, met new potential mates, or experienced sudden unpleasant sensations—all experiences for which the mice would want or need to stay awake. Throughout the experiences, the mice’s DRNDA cells kept very busy, sending bursts of dopamine to other parts of the brain.

Next, the scientists tracked DRNDA cell activity as the mice slept and woke. They found that the cells seemed to sleep when the mice did, and revved up when the mice got up.

So far, the researchers knew that the sleeping mouse/sleeping neurons and waking mouse/waking neurons pairs existed, but they couldn’t tell if the neurons caused the waking or vice versa.

To find out, they engineered DRNDA cells that could be switched on and off by light. They then bred mice with these light-sensitive cells and let them sleep. As the mice snoozed, the researchers switched on the lights and their DRNDA cells using a technique called optogenetics. Sure enough, the mice woke up.

Shutting off DRNDA cells had the opposite effect: Mice with no DRNDA activity couldn’t keep their eyes open, even when faced with danger, loud noises, or the possibility of mating.

The authors note that their experiments included only mice, and that it’s too soon to draw conclusions about what this might mean for people.

“Further work is necessary to establish causation in humans,” Gradinaru said, “and to test the potential of the DRNDA as a therapeutic target for insomnia or oversleeping, and for sleep disturbances that accompany other psychiatric disorders such as depression, bipolar disorder, and schizophrenia."

Why Thousands of 'Penis Fish' Washed Up on a California Beach

Kate Montana, iNaturalist // CC BY-NC 4.0
Kate Montana, iNaturalist // CC BY-NC 4.0

Nature works in mysterious ways. The latest example materialized at Drakes Beach near San Francisco, California, in early December, when visitors strolling along the shore stumbled upon what looked to be the discarded inventory of an adult novelty shop. In fact, it was thousands of Urechis caupo, a marine worm that bears more than a passing resemblance to a human penis.

The engorged pink invertebrate, which is typically 10 inches in length, is native to the Pacific coast and frequently goes by the less salacious name of “fat innkeeper worm.” Burrowing in sand, the worm produces mucus from its front end to ensnare plankton and other snacks, then pumps water to create a vacuum where the food is directed into their tunnel. Since it builds up a small nest of discarded food, other creatures like crabs will stop by to feed, hence the “innkeeper” label.

You can see the worm in "action" here:

Because the worms enjoy a reclusive life in their burrows, it’s unusual to see thousands stranded on the beach. It’s likely that a strong storm broke up the intertidal sand, decimating their homes and leaving them exposed. The event is likely to thrill otters, as they enjoy dining on the worm. So do humans: Penis fish are served both raw and cooked in Korea and China.

[h/t Live Science]

The Horrors of Anglerfish Mating

Masaki Miya et al. "Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective," BMC Evolutionary Biology 10, article number: 58 (2010), Wikimedia Commons // CC BY 2.0
Masaki Miya et al. "Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective," BMC Evolutionary Biology 10, article number: 58 (2010), Wikimedia Commons // CC BY 2.0

When you think of an anglerfish, you probably think of something like the creature above: Big mouth. Gnarly teeth. Lure bobbing from its head. Endless nightmares. 

During the 19th century, when scientists began to discover, describe, and classify anglerfish from a particular branch of the anglerfish family tree—the suborder Ceratioidei—that’s what they thought of, too. The problem was that they were only seeing half the picture. The specimens that they were working with were all female, and they had no idea where the males were or what they looked like. Researchers sometimes found some other fish that seemed to be related based on their body structure, but they lacked the fearsome maw and lure typical of ceratioids and were much smaller—sometimes only as long as 6 or 7 millimeters—and got placed into separate taxonomic groups.

It wasn’t until the 1920s—almost a full century after the first ceratioid was entered into the scientific record—that things started to become a little clearer. In 1922, Icelandic biologist Bjarni Saemundsson discovered a female ceratioid with two of these smaller fish attached to her belly by their snouts. He assumed it was a mother and her babies, but was puzzled by the arrangement.

“I can form no idea of how, or when, the larvae, or young, become attached to the mother. I cannot believe that the male fastens the egg to the female,” he wrote. “This remains a puzzle for some future researchers to solve.”

When Saemundsson kicked the problem down the road, it was Charles Tate Regan, working at the British Museum of Natural History in 1924, who picked it up. Regan also found a smaller fish attached to a female ceratioid. When he dissected it, he realized it wasn’t a different species or the female angler’s child. It was her mate.

The “missing” males had been there all along, just unrecognized and misclassified, and Regan and other scientists, like Norwegian zoologist Albert Eide Parr, soon figured out why the male ceratioids looked so different. They don’t need lures or big mouths and teeth because they don’t hunt, and they don’t hunt because they have the females. The ceratioid male, Regan wrote, is “merely an appendage of the female, and entirely dependent on her for nutrition.” In other words, a parasite.

When ceratioid males go looking for love, they follow a species-specific pheromone to a female, who will often aid their search further by flashing her bioluminescent lure. Once the male finds a suitable mate, he bites into her belly and latches on until his body fuses with hers. Their skin joins together, and so do their blood vessels, which allows the male to take all the nutrients he needs from his host/mate’s blood. The two fish essentially become one.

With his body attached to hers like this, the male doesn't have to trouble himself with things like seeing or swimming or eating like a normal fish. The body parts he doesn’t need anymore—eyes, fins, and some internal organs—atrophy, degenerate, and wither away, until he’s little more than a lump of flesh hanging from the female, taking food from her and providing sperm whenever she’s ready to spawn.

Extreme size differences between the sexes and parasitic mating aren’t found in all anglerfish. Throughout the other suborders, there are males that are free-swimming their whole lives, that can hunt on their own and that only attach to the females temporarily to reproduce before moving along. For deep-sea ceratioids that might only rarely bump into each other in the abyss, though, the weird mating ritual is a necessary adaptation to keep mates close at hand and ensure that there will always be more little anglerfish. And for us, it’s something to both marvel and cringe at, a reminder that the natural world is often as strange as any fiction we can imagine.

Naturalist William Beebe put it nicely in 1938, writing, “But to be driven by impelling odor headlong upon a mate so gigantic, in such immense and forbidding darkness, and willfully eat a hole in her soft side, to feel the gradually increasing transfusion of her blood through one’s veins, to lose everything that marked one as other than a worm, to become a brainless, senseless thing that was a fish—this is sheer fiction, beyond all belief unless we have seen the proof of it.”

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