Putting Brains in Rock Machines

Lower areas of the brain have higher magnetic signals, particularly the brain stem. Credit: Stu Gilder

What happens when you cross medical science with geophysics? In one study published last year, the result was one-part interdisciplinary and one-part science fiction.

Scientists have studied the presence of a magnetic mineral, magnetite, in organisms, but work on the human brain has been far and few between. Tiny chains of magnetite crystals in the cells of magnetotactic bacteria, for example, help the bacteria swim in the right direction. Could pigeons, turtles, or even, humans, have built-in compasses too?

Stu Gilder, a geophysicist from Ludwig-Maximilian’s University in Munich, wanted to find out. He and his coauthors, many of them medical professionals, published the first systematic look at magnetite in human brains. The results reveal that humans have concentrated areas of magnetite in the more “ancient” parts of the brain.

This episode was produced by Jenessa Duncombe and mixed by Kayla Surrey.


Shane Hanlon (00:00):

Hi, Nancy.

Nanci Bompey (00:01):

Hi Shane.

Shane Hanlon (00:02):

How’s it going?

Nanci Bompey (00:03):

It’s going. How are you?

Shane Hanlon (00:06):

I’m fine.

Nanci Bompey (00:07):

So, this is an odd question because we’re obviously not lost a lot right now. We’re all in our homes. Very well-trodden paths.

Shane Hanlon (00:16):

Right. I’ve never known where I was more.

Nanci Bompey (00:17):

Yes. But have you actually ever been lost, like really lost?

Shane Hanlon (00:24):

That’s a good question. I genuinely have a good sense of direction or at least I think I do, but I have. So every summer, you’ve probably heard this on previous episodes, but I teach this field course usually, and it’s for undergraduates. And we go out and do herpetology and disease ecology, and all sorts of things. But probably my second year teaching it, so very new, I was out with the class and we were in a gully by a stream looking for salamanders because basically to find salamanders, you just flip rocks and they’re there.

Shane Hanlon (00:57):

And we walk down this stream, this creek and we got to a point where I said, “All right, everyone. That’s probably enough. You can all turn around and go back. I’ll meet you back there.” And I turned around with them and started walking. And about 20 minutes later, I realized I hadn’t seen anyone and I should be back to where we were all meeting. And probably 20 minutes after that, I realized I had no idea where the heck I was. Absolutely no idea. And thank God we were in cell phone range because I had to pull my phone out in the middle of this forest and look on Google Maps, find my little dot and then find a clearing. I walked to this clearing.

Shane Hanlon (01:38):

All the while I’m getting these frantic texts from my teaching assistant like, “Oh my God, Shane, where are you? The students are worried. I’m worried.” I did get back to them. As I approached the group, I heard a lot of snickering and some under the breath making fun of the professor. And I swallowed my pride. It was fine. It was all good. I was all safe and everything, but this was literally day one of the class. And so for the rest of the course, which was a few weeks, I never quite was able to live that down.

Nanci Bompey (02:10):

Ha, that’s funny.

Shane Hanlon (02:13):

Welcome to the American Geophysical Union’s podcast about the scientists and the methods behind the science. These are the stories you won’t read in the manuscript or hear in a lecture. I’m Shane Hanlon.

Nanci Bompey (02:22):

And I’m Nanci Bompey.

Shane Hanlon (02:24):

And this is Third Pod from the Sun.

Nanci Bompey (02:33):

Okay. But Shane, there was a reason why I asked you about being lost. It wasn’t just random.

Shane Hanlon (02:38):

Just to make fun of me.

Nanci Bompey (02:39):

Well, that is always good.

Shane Hanlon (02:42):

Right. We are talking about direction today and to talk more about this and explain what we’re going to be hearing about, we want to bring in our producer Jenessa. Hi, Jenessa.

Jenessa Duncombe (02:54):

Hi, you two.

Shane Hanlon (02:56):

So what do you got for us?

Jenessa Duncombe (02:57):

Yeah. So at Fall Meeting last year, I went to a talk that was probably the strangest talk I’ve ever been to at a conference. It was on magnetism in organisms. So there’s been a long discussion of whether animals use magnetic receptors in our brain to give us a sense of direction.

Shane Hanlon (03:16):

Like birds and stuff.

Jenessa Duncombe (03:18):

Yeah, like birds. There’s been papers on this for pigeons and bacteria, but also recently there’s been a look into humans and whether we have this in our brains too. So the talk was by a paleomagnetism researcher named Stu Gilder. He’s at the Ludwig-Maximilians-University in Munich, and Stu was presenting results on a study from 2019. Him and his team looked into this question of human brains and they actually dissected seven human brains to see their magnetic remanence.

Shane Hanlon (03:53):

I don’t… Wait, what were they looking for, though? Dissecting them for what?

Jenessa Duncombe (03:59):

So the reason they’re looking at this is knowing if humans have some kind of way of sensing direction or way of how our brains signal. That could really tell us more about human biology. And at this point, the research is really early days. What scientists are looking for is, do humans have this magnetic mineral called magnetite in our brains? And where is it? And what could that mean?

Stu Gilder (04:34):

My name is Stuart Gilder. I’m a professor of geophysics at Ludwig-Maximilians-University in Munich. I do all kinds of different things, but mostly everything I do is related to magnetism, whether it’s related to the present-day Earth’s magnetic field or the Earth’s magnetic field in the past or anything that has magnetic recorders in it, including biologic tissue.

Stu Gilder (05:04):

And one day my neighbor came into my office and my neighbor is a retired medical doctor, and he wanted to see our lab. And I made a offhanded comment that one of the new machines we were developing would be perfect to measure human brain samples and his eyes got really big and he left. And the next thing I know is he wrote a letter for me that he gave to the head of neuroanatomy at my university. My university has a famous medical school, and that’s where he studied several years ago. And he wrote this nice letter to the head.

Stu Gilder (05:51):

And the next thing I knew, I had a very nice response from… His name is Christoph Schmitz saying that yeah, we have all these brain samples and you can have them all to study. The idea was that they have a collection of human brains that were in formaldehyde since the early 1990s. The patients who had died and I guess left there their body parts for research purposes. And I’m interested in that because if it is true that they can actually detect the Earth’s magnetic field for navigation and if we can understand why then it was my thought that we could actually build better rock magnetometers.

Jenessa Duncombe (06:45):

So at this point, Stu is thinking that he can help answer a biological question ‘do humans have magnetite in our brain?’ As well as answer his own curiosities as a geophysicist. Now, magnetite has been found in other animals.

Stu Gilder (07:03):

Several people believe that nearly all species from nearly all phyla, so several species of nearly all phyla use the magnetic field for some reason. And most people think that they use it for… This magnetoreception is used for orientation to guide them. And that’s the general thought. And so birds, tortoises, bats, lobsters, fish. All kinds of different things. Bees are thought to have these magnetoreceptors, and we don’t know why.

Stu Gilder (07:49):

The one creature that I would say definitely uses the magnetic field, and I’m 100% convinced of it are these small bacteria called magnetotactic bacteria. And they absolutely have magnetite in them. They have chains of these single-domain magnets and these chains are aligned perfectly. These are the best swimming magnets in the world, and we don’t know why they are, but we do know that they do it. And again, humans have the same kind of magnetite as these magnetotactic bacteria.

Stu Gilder (08:34):

I read some papers on the human brain and most studies that were done previously up to the certain date found that there was magnetite in the brain. Nobody had really looked at the entire human brain.

Stu Gilder (09:14):

So we took one of these whole human brains, and we chopped it up into 120 pieces of about large cube size. And this is an extremely important point because the magnetization of materials scales with size. And so the bigger the piece you have, the more likely you’ll have something that’s measurable. So our philosophy was we wanted to work with very, very large samples, the largest samples we could. These are about inch size cubes or two, two and a half centimeters on a side cubes. And we systematically dissected the brain. So by dissecting it, separating it into what’s called the cerebral cortex, which is the big part of the brain and the cerebellum, which is the small part of the brain. And also the brainstem.

Stu Gilder (10:25):

We brought those pieces to one of our labs, and this particular lab is in the middle of a forest. It’s a beautiful place. This forest was given by King Maximilian in 1806, I believe, to my university. And we have called a magnetically shielded room that shields out the Earth’s magnetic field and variations of that field. And we built a clean lab for it. So there wouldn’t be any dust or potential sources of magnetic contamination.

Jenessa Duncombe (11:05):

Well, I wanted to ask you as an earth scientist, what it was like to conduct this lab work? I mean, you’re used to rock samples, right?

Stu Gilder (11:18):

Yeah. I’m not very squeamish and the brain samples, because they’ve been in formaldehyde for so many years… It’s like putty. Yeah, they have a strange texture, but they kind of look like if you’re French and you eat duck livers called foie gras. And I lived in France a long time and so it looks a lot like foie gras to me, the brain tissues. And so I’m able to separate that out.

Nanci Bompey (11:49):

Foie gras. I actually don’t think I’ve ever had foie gras. Maybe. I don’t think so.

Shane Hanlon (12:05):

Can you just say foie gras?

Nanci Bompey (12:06):

Foie gras.

Shane Hanlon (12:06):

I can’t even say it either. Yeah. Look at that. What I want to know is how does he know the texture of it?

Nanci Bompey (12:11):

If he’s a chef.

Shane Hanlon (12:12):

Is he a chef? Maybe. Yeah. Maybe that’s it. No, what’s going on Jenessa?

Jenessa Duncombe (12:19):

Yeah. It is pretty wild and I’ve never had foie gras either. And I can assure you, I never will now.

Shane Hanlon (12:28):

We’ll see. Now I’m just fascinated.

Jenessa Duncombe (12:30):

Well, so basically, once they have all these brain samples in their special magnetically shielded lab, they zap the brain samples with a super-strong magnetic field and this magnetic field… They are not messing around here. This is a field that’s a million times stronger than the Earth’s magnetic field.

Nanci Bompey (12:52):

A million times!

Jenessa Duncombe (12:54):


Shane Hanlon (12:55):

What would happen if that got out of their specially shielded room?

Jenessa Duncombe (13:00):

That sounds like a really brilliant-

Nanci Bompey (13:00):

Every magnet in the world… I actually don’t know that much about…

Shane Hanlon (13:03):

It would all point to there, right?

Nanci Bompey (13:04):

Would every magnet in the world be attracted to it? I don’t know.

Jenessa Duncombe (13:09):

That sounds like a great geo disaster movie that needs to star The Rock.

Stu Gilder (13:15):

Yes. All right. Our digression is going to turn into a movie, but no, we’ll let you get back to it.

Jenessa Duncombe (13:20):

Well, okay. Yeah. So assuming that nothing diabolical happens, they’ve now zapped the brains with this really strong magnetic field. And then the team compares how magnetic those tissues are after the strong field was applied to them. That’s called remanent magnetization. And basically on their first try, they found something really interesting.

Stu Gilder (13:44):

And I thought it would never work. And I thought we would just measure noise and it turned out most pieces acquired a remnant magnetization, a permanent magnetization that was much stronger after we had exposed it to a magnetic field. And that was proof that there was magnetic material in those pieces. It was hard for me to believe, but I wrote a report for the doctors and… You’re the first person that’s ever done this. And you don’t really know what you’re looking for or where you’re looking for it.

Stu Gilder (14:34):

I did some basic statistics on the anatomical positions. So the cerebral cortex and cerebellum and right and left and all that kind of thing. And immediately the thing that stuck out most was that the cerebellum, so the small part of the brain, the more ancient part of the brain was two or three times more magnetic on average than the cerebral cortex.

Jenessa Duncombe (15:24):

Stu needed to know if he was seeing a real signal or a fluke. So with permission, they decided to dissect six more brains coming to seven in total. Like the first brain, these had been preserved in formaldehyde since the ’90s when relatives and guardians of the deceased donated their bodies to science. Because of patient confidentiality, of course, we don’t know much about these men and women. Other than that they ranged from their mid-fifties to their late eighties when they died. And they’re from Germany.

Jenessa Duncombe (15:57):

So Stu and his team repeated the same lab process before. Sorting, cutting, slicing, and then putting these samples into Stu’s rock machine. When the data comes in, they find the exact same pattern. Each person’s brain had magnetic remanence, and the remanence was stronger in certain parts of the brain than other parts of the brain. Stu didn’t really know what to make of this because this was the first time anyone had ever systematically mapped this.

Stu Gilder (16:30):

What was amazing was that they all gave us the same pattern. So seven out of seven brains, regardless of male or female, the sex of the individual, and regardless of age of the individuals. And they all gave us the exact same pattern where the cerebellum was always really significantly more magnetic than the cerebral cortex.

Jenessa Duncombe (17:05):

For those of us not up on our brain anatomy. Here’s a quick explanation. So if you put your hand on top of your head, Nanci and Shane.

Nanci Bompey (17:16):

Doing it right now.

Jenessa Duncombe (17:17):

Good. So you’re near the upper part of your brain right now called the cere…

Shane Hanlon (17:20):

No, cerebrum.

Nanci Bompey (17:20):

No, cerebellum, right?

Jenessa Duncombe (17:24):

Cerebrum. Thank you. So it’s your cerebrum and this part of the brain has fewer little magnets in it than the lower part of our brain, according to Stu’s research. So put your hand on the back of your head now near your neck. This part of the brain area, that is where your cerebellum is and your brainstem. These are the lower parts and they control heart rate, breathing, these really base functions. And they had more magnetic material than the upper part. And Stu points out that these lower parts are the more ancient parts of our brain. So if you want to know where the magnets are at, just remember.

Nanci Bompey (18:07):

I wonder if you put a magnet up there, what would happen?

Shane Hanlon (18:10):

Let’s not find out.

Jenessa Duncombe (18:12):

Well, I was actually curious about that too. And I’ll get to that question in a minute. But first I asked Stu, did these findings have anything to do with our sense of direction, how we understand it? And sorry in advance Shane, I don’t think you’re going to be able to blame getting lost on your magnetic receptors.

Stu Gilder (18:34):

I think most people are fixated on the orientation question. So most people, when they think of magnetite, they think of compasses. We’re humans and we try to relate to our natural environment, the way that we see things and the compass and orientation seems like a natural thing. I don’t think that it’s for orientation. In all the brains that we sampled and what interests me most and I hope medical scientists will really think about is it could be that the magnetite is used as some kind of electromagnetic switching. And this is really my feeling. I have no proof to support that other than I see this gradient.

Stu Gilder (19:29):

The one thing that was interesting is one of the patients we knew was diagnosed with schizophrenia and that patient had the exact same distribution of magnetite. What was interesting with that patient was they had much more magnetite on average throughout the brain. And that again always makes me wonder, and this is why it’s nice for me to do this podcast because maybe somebody will listen and be inspired by it, is maybe schizophrenia has to do… If this electromagnetic switching is true and if you have too much magnetite in your brain, maybe you’re overstimulated, maybe this operator switch that’s trying to direct all these electrical signals through an electromagnetic switch, maybe you get overloaded.

Stu Gilder (20:32):

So if somebody was listening to that, that maybe they can get inspired. And we need more studies. We need more of that.

Jenessa Duncombe (20:43):

Something I wanted to ask is what about this research is interesting from the medical side? What are they trying to understand when it comes to magnetic remanence in human brains?

Stu Gilder (20:58):

When we applied very strong magnetic fields, we saw that we permanently magnetized these tissues. And if, if you or I held something strongly magnetic to our heads, like a cell phone or telephones have strong magnets in them, the question is, is can we permanently magnetize the brain?

Stu Gilder (21:23):

And so far, the distance is far enough away from the brain at least for the magnetic fields from phones is probably weak enough that it’s not an issue, but I had always wondered if our findings were true and you put your head next to a very strong magnet that you can permanently magnetize your brain and we should have saw that, at least in one of these seven patients. We didn’t see that and so maybe just by chance, none of these seven people ever came in contact with a strong magnet, or maybe it was that over time this strong magnetic field that the brain saw got randomized. And I think this is another esoteric question that needs to be answered.

Jenessa Duncombe (22:17):

Yeah, definitely. That’s strange to think of an imprint lasting on the brain.

Stu Gilder (22:23):

Yeah. And so I can imagine tools are made out of steel and especially in the days where steel rusted, that that can be quite magnetic. And you would imagine that somebody had to have gotten their head close to these big ships are made out of steel. And you think that someone could have permanently magnetized themselves. And what would that do?

Stu Gilder (22:54):

And this was also a question. Here’s another esoteric thing. If pigeons, for example, there are some people that really believe that pigeons use the magnetic field. There are these homing pigeons, and I’ve always wanted to stick these pigeon brains in strong magnetic fields and see whether or not we can make bad homing pigeons into good homing pigeons by aligning all of the magnetite in their brains.

Jenessa Duncombe (23:26):

Right. Interesting. Yeah.

Stu Gilder (23:30):

But I’m not going to be the person to put a live pigeon into a magnet. Somebody else can do that.

Nanci Bompey (23:37):

Honestly. I mean, pigeon brains, why not? He’s doing human brains, I wouldn’t put it past him.

Stu Gilder (23:42):

Well, there’s so many of them out there too so it’s probably not going to be that big of a deal.

Jenessa Duncombe (23:47):

Yeah. I wouldn’t be surprised. Yeah. I wouldn’t be surprised at this point.

Shane Hanlon (23:51):

All right. So maybe not pigeon brains, but what is next for him?

Jenessa Duncombe (23:55):

Well, I was really interested in what he’s doing next, but he couldn’t say other than he’s applied for a grant, he wouldn’t give any specifics.

Shane Hanlon (24:07):


Jenessa Duncombe (24:07):

It is. But he did mention that maybe they could test… They could recreate this study for fresh brain samples. What that means is instead of brains that have been sitting in formaldehyde, like the ones he used in this study, they would actually take recently deceased people’s brains.

Shane Hanlon (24:28):

Every time I hear it I’m just like brains.

Nanci Bompey (24:29):


Shane Hanlon (24:40):

All right. So on that note, that’s all from Third Pod from the Sun.

Nanci Bompey (24:45):

Thanks so much Jenessa for bringing us this story. And of course, thanks to Stu for sharing his work with us.

Shane Hanlon (24:52):

This podcast was produced by Jenessa and thanks to our sound engineer, Kayla Surrey.

Nanci Bompey (24:57):

We would love to hear your thoughts on our podcast. Please rate and review us on Apple Podcasts. You can find this podcast wherever you get your podcasts. And of course, always at thirdpodfromthesun.com.


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