Although the ability to sense magnetic fields has been a long-established fact for a multitude of animal species, experiments searching for magnetoreceptive capabilities in humans have come up empty-handed. A new study may change our view on this seeming disability, having found evidence that our brains register changes in the magnetic fields found in our environment, even when we’re completely unaware of such changes.

The mechanism behind this ability, called magnetoreception, is the ability of living cells to form nanocrystals made out of magnetite, a ferromagnetic mineral that the organism, in turn, uses to sense magnetic fields. This ability has been demonstrated to be used by various species of bacteria, insects, birds, and even whales, rodents, bats and cows; magnetoreception in dogs is acute enough for them to be trained to find hidden magnets, and it has been found that they prefer to poop along a north-south orientation, for some odd reason. Dog works in mysterious ways…

But this magnetoreceptive ability is absent in humans for some reason—or at least it seems to be, despite the presence of these same magnetite crystal formations being present in human brain tissue. To solve that mystery, a group of researchers from the California Institute of Technology and Matani Laboratory in Tokyo devised a new experiment to see if humans can indeed, at least on a subconscious level, sense magnetic fields.

The study consisted of 34 volunteers who were placed in a special chamber that isolated them from the Earth’s magnetic field, but could generate and control artificial magnetic fields within it. The subjects’ brain activity was recorded using electroencephalograph (EEG) equipment, to see how they were responding neurologically to the changes in the magnetic fields generated within the chamber.

When we voluntarily turn our heads, this is a move that the brain expects, so if there is any effect of the Earth’s magnetic field on our biology we typically wouldn’t notice. However, the controlled changes in the magnetic fields generated within the experiment’s chambers would be outside the control of the test subjects’ brains, meaning that if they were indeed sensing the planet’s magnetic field, it would register in their brain patterns as if they had been involuntarily moved, despite the subjects having remained perfectly still in their seats. 

Predictably, the subjects did not consciously perceive any shifting of the magnetic fields. However, the EEG readings “revealed that certain magnetic field rotations could trigger strong and reproducible brain responses,” according to an article written by the study’s authors, published in The Conversation. One EEG pattern known as “alpha-ERD” (event-related desynchronization) showed that the subjects’ brains were “concerned” that they had apparently changed position. 

Alpha-ERD patterns typically appear when a person suddenly detects and processes an incoming sensory stimulus—in this case, the patterns shrink under these conditions—implying that their brains were reacting to a movement that had been registered, despite the only movement being the rotation of the magnetic fields. The study authors note that “such alpha-ERD patterns in response to simple magnetic rotations is powerful evidence for human magnetoreception,” with some of the participants’ Alpha-ERD patterns dropping by half their normal strength.

Interestingly, the subjects’ brains seemed to respond only to naturally-occurring magnetic orientations, and registered no response to artificial ones. “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,” the authors explain. “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.”

This seeming oddity makes sense in light of how other magnetoreceptive animals only seem to respond to relevant magnetic signals and ignore anomalous ones, such as a lighting strike or lodestone deposit in the ground. For instance, one study on robins shows that the birds stop using the geomagnetic field if the strength is more than approximately 25 percent different from what they’re accustomed to; basically, their brains are filtering out information that isn’t relevant, in the same way our brains will ignore background noise so that we can concentrate on something we’re trying to listen to. The researchers suspect that this effect may have prevented earlier experiments into human magnetoreception from succeeding: if the researchers had turned up the strength of the magnetic fields in an attempt to make them more noticeable for the subjects, they may have inadvertently caused their brains to ignore the stronger fields altogether.

“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,” according to the article. The study authors wonder if individuals with weak magnetoreceptive abilities could be trained to improve this ability, and could those with a strong sense actually learn to consciously sense the Earth’s magnetic field? Regardless of whether or not we can deliberately develop this ability, the experiment suggests that it is indeed a real phenomenon.

“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.”

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