The Night Shift

The sponge would not clean itself.

Maya had cut it into the shape of a brain, more or less, and Soren had threaded thin aquarium tubing through it to be the blood vessels. They had squeezed blue food dye into the middle to be the waste. Now they were pushing clear water through the tubes to flush the blue out, and it was not flushing.

"It's just sitting there," Maya said. She poked the sponge. A little blue leaked, then stopped.

"The tubes aren't touching the middle," Soren said. He turned the sponge over under the desk lamp. "The water goes through the vessels, but the blue is out here, in the sponge part. Between everything."

"So it's stuck."

"It's stuck."

Maya sat back. The project was due at eight in the morning. Soren had the assignment sheet propped against a mug. It said, in their teacher Mr. Okafor's tight handwriting, Show how the brain removes waste. Mr. Okafor had told them the brain had no lymph vessels like the rest of the body, and had left it there, the way he left a lot of things, half a step short of the interesting part.

"Okay," Maya said. "If the vessels don't reach the blue, how does the real brain get the blue out."

"I don't know. That's the whole problem." Soren picked up his pen and wrote sponge holds waste, vessels don't reach it. He looked at what he had written. "Wait. Squeeze it."

"What?"

"Squeeze the sponge while the water's running."

Maya squeezed. Blue came out of the middle in a cloud, swirled into the clear water, and washed away down the tubing.

They both stared.

"It only cleans when you squash it," Maya said slowly.

"When the sponge changes shape, the spaces open and the water gets in between," Soren said. "When it's just sitting there, full size, the water can't reach."

"So the brain would have to squash." Maya let go. The sponge puffed back. "Brains don't squash. Yours doesn't get smaller when you think."

"No." Soren was quiet, turning the pen. "But something has to change. The water only moved when something changed."

Maya's mother put her head around the door. "It's ten thirty," she said. "Whatever this is, it needs to be a morning problem."

"It's a night problem," Maya said. "That's kind of the point, we just don't know why yet."

Her mother made the face that meant five more minutes and disappeared.

Soren was reading something on the tablet, the light on his face. "Maya. The brain cells shrink."

"They what."

"When you're asleep. It's a real thing, I found the study." He read fast. "The cells in your brain pull in a little when you sleep. They get smaller. And the space between them gets bigger. Like almost a fifth bigger."

Maya looked at the sponge. She squeezed it again and watched the blue leave the middle.

"The gaps open," she said.

"The gaps open. And the fluid rushes through the gaps and washes the waste out. Real waste. Junk the cells make all day just from working." Soren scrolled. "And it says the flushing runs about ten times faster asleep than awake."

"Ten times."

"Ten times. It basically doesn't happen when you're awake. Not really. It waits."

Maya sat very still with the sponge in her hand, blue water running down her wrist.

"So all day," she said, "the junk just builds up. In the gaps. And you can't get it out because you're using the brain."

"You can't clean the thing while you're running it."

"And at night the cells pull back and the water comes in and washes the whole day out of you." She looked up. "Soren. Every night. While we're just lying there doing nothing."

"We're not doing nothing." He had stopped scrolling. "That's the part. It looks like nothing."

That landed on both of them at the same time.

"People always say sleep is wasted time," Maya said. "My cousin brags about how little he sleeps. Like it makes him better."

"It's the opposite of wasted." Soren was writing again, fast. "It's the only time the cleaning happens. You lie down and go still and the whole inside of your head opens up and the river runs through it."

Maya read over his shoulder. One line said, the proteins it washes out are the same ones that pile up in Alzheimer's. She read it twice.

"So the stuff that gets left behind," she said. "If it never got washed. If it just stayed."

"Nobody's saying that for sure yet." Soren tapped the tablet. "They're still figuring it out. That's what it says. Still figuring it out."

Maya liked that better than an answer. She sat with the sponge and thought about being asleep, right now, tonight, hours from now, her own head going quiet and the cells drawing in and the space widening in the dark and the fluid moving through her like a tide coming into a bay while she dreamed about nothing and cleaned herself out.

"We can't show them a brain that squashes," she said. "We have to show them one that opens."

"We show them the sponge," Soren said. "And we make them squeeze it."

Maya set the sponge in the tray, dry side up, waiting for morning.

Under the lamp the blue that was left in the middle sat perfectly still, going nowhere, waiting for the room to go dark.