Hank: Pretty soon, figuring out your blood type might be as easy as squeezing a drop of blood onto a piece of paper.

Last week, a team of Chinese researchers reported in the journal Science Translational Medicine that they’d come up with a new test to see whether you have A, B, AB, or O blood, in as few as 30 seconds. Because you barely need any equipment or time, this invention could help with emergency blood transfusions and save lives.

Your blood type is determined by what kind of antigens decorate the outside of your red blood cells. Antigens are sugars and proteins that immune systems can recognize, to help defend against foreign invaders. If you have the A antigen, you have type A blood; if you have the B antigen, you have B blood; if you have both, you’re AB; and if you have neither, you’re O.

Normally, blood testing involves two methods to make sure it’s right. Because picking the wrong blood for a transfusion can make your immune system go haywire and, like kill you.

Forward testing checks for antigens, by mixing a blood sample with either A or B antibodies. If you have A antigens, it’ll clump with A antibodies. But not with B antibodies. Reverse, or back, testing, does the opposite. It checks for what antibodies you have in the liquid part of your blood, called plasma, by seeing if it clumps with red blood cells known to have A or B antigens.

So, reverse testing is a great way to double-check your forward result. But even the speediest labs have to centrifuge your blood to get the plasma, and can’t do the test much faster than 10 minutes. If you’re seriously hurt on a battlefield, you don’t have the equipment or time for that!

Enter the paper test. It still relies on the fact that antibodies and antigens clump together, but it uses a dye that changes color depending on whether it touches whole blood or just plasma. After you drip some blood on a forward test strip, it runs into A and B antibodies that are dried onto the paper, before reaching two patches of dye.

If you have type A blood, red blood cells will clump on the A antibody side, so only the plasma will reach the dye, turning it a teal color. Nothing will clump on the B side, so the full sample will reach the dye and turn it brown. So whether one, both, or neither side turns teal, you can figure out your blood type.

For double-checking, they made a strip with the reverse test on it too. It has a thin membrane that filters the blood so the plasma can be checked for antibodies, either forming clumps or not before touching the dye.

When the researchers tested their invention, they got the forward result in 30 seconds and the reverse one in 2 minutes, with 99.9% accuracy. These paper tests aren’t being used by doctors yet, but the researchers hope we’ll be seeing them in the next year or two.

Now, while some scientists are studying blood, others are studying blood flow in the brain. Specifically, in a paper this week in Nature Communications, a team of neuroscientists discovered how certain brain regions act differently when we’re navigating with or without help from GPS. The researchers had 24 volunteers take a 2 hour virtual tour through Soho, a fashionable district in the West End of London, to learn the area.

And the next day, the volunteers were quizzed about how to get from various point As to point Bs. Everything was still virtual: the scientists made videos of the walking routes, which paused at intersections. Then, they told participants which way to go, or asked them to choose – kind of like a Google Maps Choose-Your-Own-Adventure.

While all this was happening, they monitored the volunteers’ brains with an fMRI machine, to see if different regions became more active with different kinds of routes. The researchers found that the back part of the right hippocampus was active when people who were actively navigating entered new streets, especially when there was a change in the number of connecting streets. But when the volunteers didn’t have to choose where to go next – kind of like blindly following GPS instructions – their hippocampi hardly lit up.

We know the hippocampus is important for spatial memory, but we haven’t been so sure how it’s involved in navigation. In this experiment, the scientists think the hippocampus is keeping track of all the possible walking paths, to help you simulate different ways your journey could go. And if you’re just passively following instructions, and not using your hippocampus, you might not actually be learning how to get around.

These results fit with a previous experiment done with London taxi cab drivers, who need to pass a notoriously difficult test covering London’s 25,000 or so streets in a 10 kilometer radius.

Researchers imaged the brains of drivers before they started training, and again three to four years later, after they took the test. And people who passed the test actually gained more brain tissue in the back of their hippocampus than those who failed. So, if you want to give your brain a good workout, maybe pass on the GPS if you don't definitely need it.

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