We've learned a lot about how the human brain works, but there are still new discoveries and mysteries each year.

And this past year was no exception. From internal compasses, to mysterious sniffers, to brain-washing — no, not like that — here are three ways the brain surprised us in 2019. [ ♪INTRO ].

First, in March, scientists published evidence in the journal eNeuro that humans may be able to sense Earth's magnetic field. We know an internal compass exists in a lot of animals, like migratory birds and sea turtles, and we've suspected it might be present in humans, too. But no one had been able to provide solid evidence for that — so last year, scientists took another run at the problem.

They asked a group of about 30 volunteers to — one-at-a-time — climb into a special, room-sized device designed to block the Earth's magnetic field. The device had two main components: an external Faraday cage, which blocks magnetic fields, and internal coils that could create an artificial magnetic field — one the scientists could control. So basically, the only magnetic fields the participants experienced were the ones for the experiment.

In the study, the test subjects sat in a wooden chair in the center of the room, in the dark, while the scientists manipulated their artificial magnetic field. They turned it this way and that way as if the person was turning around. Kind of like virtual reality, but for magnetism.

Meanwhile, an EEG machine monitored the volunteers' brain activity — specifically, their alpha waves, which are seen when someone is awake, but resting. Then, the scientists combined all the participants' data sets and analyzed them. They found that certain changes in the artificial magnetic field appeared to trigger changes in the participants' alpha waves.

It was as if the brain suddenly noticed an abrupt change, suggesting there really is something in our brains that can sense magnetism. That said, the scientists don't know what that mechanism is, if it does exist. They suggested it could have something to do with magnetite crystals: iron compounds we've found in other animals that can function like biological magnets.

Where these might be located in our brains... we don't know. But one way or another, this study was still really helpful for the field, and it will be interesting to explore this more in the future. Next, moving from “things we're trying to find” to “things that are missing”!

In November, scientists announced in the journal Neuron that they'd found people who could smell without olfactory bulbs. Our olfactory bulbs are located just above the nasal cavity, and they're a part of our brain responsible for receiving and processing nerve signals from our noses. Basically, they allow you to smell stuff.

Except… maybe that's not the whole story. Last year, a group of scientists, working on a completely different study, were using. MRI brain scans to look at the olfactory bulbs of volunteers.

And they found something unusual: a 29-year old woman without olfactory bulbs. Not having these things isn't unheard of, but what was confusing is that the woman said she could smell just fine. And this wasn't a one-off case.

As the researchers were building a control group for their study, they found another woman who also could smell without olfactory bulbs. And tests backed up these claims. With the exception of one type of fruity-smelling chemical, the women had normal senses of smell.

But how? Well, we don't know yet. The scientists weren't able to detect any other differences in their brains, compared to the control group.

So maybe this is an example of just how the brain can adapt when some structure is missing. Or… maybe not. Other scientists have pointed out that it's possible there may be something there that just didn't show up on the MRI.

Maybe the women had really small olfactory bulbs. In any case, something is going on. And also?

There's a final twist in this mystery, too. After scientists combed through a database of about a thousand people's brain scans, they suggested this condition — whatever it is — might be associated with being female and being left-handed. Based on that database, they estimated that about 1 in every 200 women, and maybe 1 in every 25 left-handed women, might be mystery sniffers.

Admittedly, it does sound like a bit of a stretch, given how small their sample size was. And we definitely need more data about it. But the authors, at least, think there's a correlation here.

So if they're right, maybe there's something even cooler to be found this year. Finally, from sniffers to sleepers! Also in November, researchers announced in the journal Science that our bodies may naturally kind of “wash” our brains while we sleep.

See, like I said earlier… not that kind of brain-washing. Although you're not awake to experience it, a lot is going on in your brain while you sleep, including changes to brain waves and blood flow. But scientists have also detected changes in the amount of cerebrospinal fluid, also called CSF.

It's a clear, colorless fluid that surrounds, cushions, and protects the brain, and it can also carry things like antibodies. In this new study, though, the scientists wanted to know exactly what the CSF was doing. So they used MRI and EEG machines to watch what was happening in 13 people's brains during dreamless sleep.

And they found something pretty cool. They discovered that CSF seems to flow in and out of the brain in waves, about one every 20 seconds. This happened more-or-less in sync with certain brain waves and opposite cycles of blood flow.

As the blood goes in, the CSF goes out, and vice versa. The scientists think these waves of fluid might be important for maintaining our brain's health, and they might even be a missing link in how we understand sleep. For instance, as your sleeping brain is solidifying memories or doing whatever else, it looks like waves of CSF might help flush out toxic, memory-impairing proteins or other waste.

So now, the scientists think investigating how CSF flow changes could be a way into studying conditions associated with sleep, like insomnia. At the end of the day, our brains are super weird. They seem to go through a wash cycle, might have bits we haven't found yet, and might not need all the bits they do have!

But for as strange as they are, they're absolutely fascinating. And the more we learn about them, the more we'll understand a big part of what makes us who we are. Thanks for watching this episode of SciShow Psych!

If you want to help us make more content like this in the New Year, you can head over to patreon.com/scishow. Our patrons are an amazing community of people who love to learn, and they're the ones who voted for us to create SciShow Psych in the first place. So, to all our current patrons, thank you!

This show literally wouldn't exist without you. Happy new year! [ ♪OUTRO ].