Quantcast
Connect with us

New evidence for a human magnetic sense that lets your brain detect the Earth’s magnetic field

Published

on

Do human beings have a magnetic sense? Biologists know other animals do. They think it helps creatures including bees, turtles and birds navigate through the world.

Scientists have tried to investigate whether humans belong on the list of magnetically sensitive organisms. For decades, there’s been a back-and-forth between positive reports and failures to demonstrate the trait in people, with seemingly endless controversy.

The mixed results in people may be due to the fact that virtually all past studies relied on behavioral decisions from the participants. If human beings do possess a magnetic sense, daily experience suggests that it would be very weak or deeply subconscious. Such faint impressions could easily be misinterpreted – or just plain missed – when trying to make decisions.

So our research group – including a geophysical biologist, a cognitive neuroscientist and a neuroengineer – took another approach. What we found arguably provides the first concrete neuroscientific evidence that humans do have a geomagnetic sense.

How does a biological geomagnetic sense work?

Life on Earth is exposed to the planet’s ever-present geomagnetic field that varies in intensity and direction across the planetary surface.
Nasky/Shutterstock.com

The Earth is surrounded by a magnetic field, generated by the movement of the planet’s liquid core. It’s why a magnetic compass points north. At Earth’s surface, this magnetic field is fairly weak, about 100 times weaker than that of a refrigerator magnet.

Over the past 50 years or so, scientists have shown that hundreds of organisms in nearly all branches of the bacterial, protist and animal kingdoms have the ability to detect and respond to this geomagnetic field. In some animals – such as honey bees – the geomagnetic behavioral responses are as strong as the responses to light, odor or touch. Biologists have identified strong responses in vertebrates ranging from fish, amphibians, reptiles, numerous birds and a diverse variety of mammals including whales, rodents, bats, cows and dogs – the last of which can be trained to find a hidden bar magnet. In all of these cases, the animals are using the geomagnetic field as components of their homing and navigation abilities, along with other cues like sight, smell and hearing.

ADVERTISEMENT

Skeptics dismissed early reports of these responses, largely because there didn’t seem to be a biophysical mechanism that could translate the Earth’s weak geomagnetic field into strong neural signals. This view was dramatically changed by the discovery that living cells have the ability to build nanocrystals of the ferromagnetic mineral magnetite – basically, tiny iron magnets. Biogenic crystals of magnetite were first seen in the teeth of one group of mollusks, later in bacteria, and then in a variety of other organisms ranging from protists and animals such as insects, fish and mammals, including within tissues of the human brain.

Chains of magnetosomes from a sockeye salmon.
Mann, Sparks, Walker & Kirschvink, 1988, CC BY-ND

Nevertheless, scientists haven’t considered humans to be magnetically sensitive organisms.

Manipulating the magnetic field

Schematic drawing of the human magnetoreception test chamber at Caltech.
Modified from ‘Center of attraction’ by C. Bickel (Hand, 2016).

In our new study, we asked 34 participants simply to sit in our testing chamber while we directly recorded electrical activity in their brains with electroencephalography (EEG). Our modified Faraday cage included a set of 3-axis coils that let us create controlled magnetic fields of high uniformity via electric current we ran through its wires. Since we live in mid-latitudes of the Northern Hemisphere, the environmental magnetic field in our lab dips downwards to the north at about 60 degrees from horizontal.

In normal life, when someone rotates their head – say, nodding up and down or turning the head from left to right – the direction of the geomagnetic field (which remains constant in space) will shift relative to their skull. This is no surprise to the subject’s brain, as it directed the muscles to move the head in the appropriate fashion in the first place.

ADVERTISEMENT

Study participants sat in the experimental chamber facing north, while the downwards-pointing field rotated clockwise (blue arrow) from northwest to northeast or counterclockwise (red arrow) from northeast to northwest.
Magnetic Field Laboratory, Caltech, CC BY-ND

In our experimental chamber, we can move the magnetic field silently relative to the brain, but without the brain having initiated any signal to move the head. This is comparable to situations when your head or trunk is passively rotated by somebody else, or when you’re a passenger in a vehicle which rotates. In those cases, though, your body will still register vestibular signals about its position in space, along with the magnetic field changes – in contrast, our experimental stimulation was only a magnetic field shift. When we shifted the magnetic field in the chamber, our participants did not experience any obvious feelings.

The EEG data, on the other hand, revealed that certain magnetic field rotations could trigger strong and reproducible brain responses. One EEG pattern known from existing research, called alpha-ERD (event-related desynchronization), typically shows up when a person suddenly detects and processes a sensory stimulus. The brains were “concerned” with the unexpected change in the magnetic field direction, and this triggered the alpha-wave reduction. That we saw such alpha-ERD patterns in response to simple magnetic rotations is powerful evidence for human magnetoreception.

Video shows the dramatic, widespread drop in alpha wave amplitude (deep blue color on leftmost head) following counterclockwise rotations. No drop is observed after clockwise rotation or in the fixed condition. Connie Wang, Caltech

Our participants’ brains only responded when the vertical component of the field was pointing downwards at about 60 degrees (while horizontally rotating), as it does naturally here in Pasadena, California. They did not respond to unnatural directions of the magnetic field – such as when it pointed upwards. We suggest the response is tuned to natural stimuli, reflecting a biological mechanism that has been shaped by natural selection.

Other researchers have shown that animals’ brains filter magnetic signals, only responding to those that are environmentally relevant. It makes sense to reject any magnetic signal that is too far away from the natural values because it most likely is from a magnetic anomaly – a lighting strike, or lodestone deposit in the ground, for example. One early report on birds showed that robins stop using the geomagnetic field if the strength is more than about 25 percent different from what they were used to. It’s possible this tendency might be why previous researchers had trouble identifying this magnetic sense – if they cranked up the strength of the magnetic field to “help” subjects detect it, they might have instead ensured that subjects’ brains ignored it.

ADVERTISEMENT

Moreover, our series of experiments show that the receptor mechanism – the biological magnetometer in human beings – is not electrical induction, and can tell north from south. This latter feature rules out completely the so-called “quantum compass” or “cryptochrome” mechanism which is popular these days in the animal literature on magnetoreception. Our results are consistent only with functional magnetoreceptor cells based on the biological magnetite hypothesis. Note that a magnetite-based system can also explain all of the behavioral effects in birds that promoted the rise of the quantum compass hypothesis.

Brains register magnetic shifts, subconsciously

Our participants were all unaware of the magnetic field shifts and their brain responses. They felt that nothing had happened during the whole experiment – they’d just sat alone in dark silence for an hour. Underneath, though, their brains revealed a wide range of differences. Some brains showed almost no reaction, while other brains had alpha waves that shrank to half their normal size after a magnetic field shift.

It remains to be seen what these hidden reactions might mean for human behavioral capabilities. Do the weak and strong brain responses reflect some kind of individual differences in navigational ability? Can those with weaker brain responses benefit from some kind of training? Can those with strong brain responses be trained to actually feel the magnetic field?

A human response to Earth-strength magnetic fields might seem surprising. But given the evidence for magnetic sensation in our animal ancestors, it might be more surprising if humans had completely lost every last piece of the system. Thus far, we’ve found evidence that people have working magnetic sensors sending signals to the brain – a previously unknown sensory ability in the subconscious human mind. The full extent of our magnetic inheritance remains to be discovered.The Conversation

ADVERTISEMENT

Shinsuke Shimojo, Gertrude Baltimore Professor of Experimental Psychology, California Institute of Technology; Daw-An Wu, , California Institute of Technology, and Joseph Kirschvink, Nico and Marilyn Van Wingen Professor of Geobiology, California Institute of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Report typos and corrections to [email protected].
READ COMMENTS - JOIN THE DISCUSSION
Continue Reading

Facebook

White House either lied or there was ‘gross mismanagement’ for not knowing Shanahan’s past: David Gergen

Published

on

On Tuesday, acting Secretary of Defense Patrick Shanahan withdrew his nomination as new details came to life about a violent series of domestic disputes within his family, including an incident in which he defended his son for assaulting his wife with a baseball bat.

Former White House official David Gergen scorned the idea that the White House and Senate Republicans were not aware of this information, noting that Shanahan was already confirmed to a high-ranking office in the Pentagon and would have already undergone a rigorous FBI background check.

Continue Reading

Breaking Banner

Nancy Pelosi says White House attempt to block Hope Hicks testimony is ‘obstruction of justice’

Published

on

Nancy Pelosi clap

President Donald Trump's White House is committing obstruction of justice by claiming Hope Hicks has "immunity" from testifying before Congress about her time in the administration and even transition.

Speaker of the House Nancy Pelosi was asked about the administration's contention by CNN congressional reporter Manu Raju.

Pelosi replied that it was, "obstruction of justice."

The answer could be important as Congressional precedence says that obstruction of justice is a high crime or misdemeanor worthy of impeachment.

Continue Reading
 

Breaking Banner

Ocasio-Cortez dunks on Liz Cheney again for using Nazi language to defend Trump: ‘Enjoy defending concentration camps’

Published

on

Dick Cheney's daughter continued to receive ferocious backlash after she falsely claimed that Donald Trump's tent cities are not "concentration camps."

Rep. Liz Cheney (R-WY) demanded Rep. Alexandria Ocasio-Cortez (D-NY) learn history -- while revealing she knew little -- during a Twitter outburst.

“The U.S. is running concentration camps on our southern border and that is exactly what they are. … ‘Never Again’ means something ... we need to do something about it," Ocasio-Cortez noted.

Continue Reading
 
 

Copyright © 2019 Raw Story Media, Inc. PO Box 21050, Washington, D.C. 20009 | Masthead | Privacy Policy | For corrections or concerns, please email [email protected]

I need your help.

Investigating Trump's henchmen is a full time job, and I'm trying to bring in new team members to do more exclusive reports. We have more stories coming you'll love. Join me and help restore the power of hard-hitting progressive journalism.

TAKE A LOOK
close-link

Investigating Trump is a full-time job, and I want to add new team members to do more exclusive reports. We have stories coming you'll love. Join me and go ad-free, while restoring the power of hard-hitting progressive journalism.

TAKE A LOOK
close-link