George Dvorsky, Gizmodo, Mar 18, 2019
New experimental evidence published today in the science journal eNeuro suggests the human brain is capable of responding to the Earth’s magnetic field, though at an unconscious level. It’s not clear if our apparent ability to sense the magnetic field is in any way useful, as it’s likely a vestigial trait left over from our more primitive past. Giving the new finding, however, researchers should investigate further to determine if magnetoreception is somehow contributing to our behavior or abilities, such as spatial orientation.
Magnetoreception is found among both invertebrates and vertebrates, and it’s probably a capacity that’s been around for a very long time. Some bacteria and protozoans exhibit magnetoreception, as do some migratory birds and sea turtles, who use the added sense to assist with navigation. Dogs are also sensitive to the Earth’s magnetic field, orienting their bodies along the North-South axis when they poop.
“There is no such thing as ‘extra-sensory perception’. What we have shown is this is a proper sensory system in humans, just like it is in many animals.”Around 30 years ago, scientists tried to determine if humans have a similar capacity, but to no avail. These pioneering efforts produced results that were either inconclusive or unreproducible, so scientists largely gave up, figuring magnetoreception is something outside the human realm. In the years that followed, work on animals increasingly pointed to magnetoreception as the result of complex neurological processing—a possibility that motivated Caltech geophysicist Joseph Kirschvink and neuroscientist Shin Shimojo to revisit the issue.
“Our approach was to focus on brainwave activity alone,” Kirschvink told Gizmodo. “If the brain is not responding to the magnetic field, then there is no way that the magnetic field can influence someone’s behavior. The brain must first perceive something in order to act on it—there is no such thing as ‘extra-sensory perception.’ What we have shown is this is a proper sensory system in humans, just like it is in many animals.”
To test whether the human brain is capable of magnetoreception, and to do so in a reliable, believable manner, Kirschvink and Shimojo set up a rather elaborate experiment involving a chamber specially designed to filter out any extraneous interference that might influence the results.
Picture caption: Illustration of the experimental setup.
During carefully controlled experiments, participants sat upright in the chair with their heads positioned near the center of the magnetic field, while EEG data was collected from 64 electrodes. The hour-long tests, in which the direction of the magnetic fields were rotated repeatedly, were performed in total darkness. The experiment involved 34 adult volunteers, who collectively participated in hundreds of trials; all tests were done in a double blind manner, and control groups were also included.
After the experiments, none of the participants said they could tell when or if any change to the magnetic field had occurred. But for four of the 34 participants, the EEG data told a different story.
Picture caption: EEG data showing strength of alpha waves, as influenced by magnetic fields. Image: Wang et al., eNeuro (2019)
The alpha rhythm is the dominant brain wave produced by neurons when individuals aren’t processing any specific sensory information or performing a specific task. When “stimulus is suddenly introduced and processed by the brain, the alpha rhythm generally decreases,” the authors wrote. The drop in alpha waves observed during these experiments suggested the brain interpreted the magnetic fields as some kind of stimulus—the neurological purpose or result of which is unclear. But as the new study pointed out, this observation now “provides a basis to start the behavioral exploration of human magnetoreception.”
The researchers don’t know how the human brain is able to sense magnetic fields, but Kirschvink has a favorite theory. There may be “specialized sensory cells that contain tiny magnetite crystals,” he said, which is currently “the only theory that explains all of the results, and for which there is direct physiological data in animals.” Back in 1992, Kirschvink and his colleagues isolated crystals of biogenic magnetite from human brains, so he may be onto something; other researchers should now dive into this possibility to flesh this idea out.
“Magnetoreception is a normal sensory system in animals, just like vision, hearing, touch, taste, smell, gravity, temperature, and many others,” Kirschvink told Gizmodo. “All of these systems have specific cells that detect the photon, sound wave, or whatever, and send signals from them to the brain, as does a microphone or video camera connected to a computer. But without the software in the computer, the microphone or video camera will not work. We are saying that human neurophysiology evolved with a magnetometer—most likely based on magnetite—and the brain has extensive software to process the signals.”
Looking ahead, Kirschvink would like to better understand the biophysics of this capacity, including measuring threshold sensitives. Shimojo believes it might be possible to bring magnetoreception into conscious awareness, a possibility that could spawn entirely new directions of research. Imagine, for example, if future humans had a built-in compass, allowing them to sense magnetic north.
Michael Winklhofer from the Institute of Biology and Environmental Sciences at Carl von Ossietzky University of Oldenburg, liked the new study, saying the authors “did everything to rule out artifacts [noise] which could easily occur during recording electrical brain activity in a changing magnetic field.” Also, the description of the setup and methods was so detailed that the study can be easily replicated, he said.
“For the first time in humans, clear responses to magnetic field changes were observed. Even though the magnetic field was not consciously perceived in the test persons that showed brain responses to the field, the study invites [other scientists] to follow up research to understand the mechanism by which the magnetic field elicits neuronal activity,” Winklhofer told Gizmodo.
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Transduction of the Geomagnetic Field as Evidenced from Alpha-band Activity in the Human Brain
Abstract
Although many migrating and homing animals are sensitive to Earth’s magnetic field, most humans are not consciously aware of the geomagnetic stimuli that we encounter in everyday life. Either we have lost a shared, ancestral magnetosensory system, or the system lacks a conscious component with detectable neural activity but no apparent perceptual awareness by us. We found two classes of ecologically-relevant rotations of Earth-strength magnetic fields that produce strong, specific and repeatable effects on human brainwave activity in the EEG alpha band (8-13 Hz); EEG discriminates in response to different geomagnetic field stimuli. Biophysical tests rule out all except the presence of a ferromagnetic transduction element, such as biologically-precipitated crystals of magnetite (Fe3O4).
Conclusion
Our results indicate that at least some modern humans transduce changes in Earth-strength magnetic fields into an active neural response. We hope that this study provides a road-map for future studies aiming to replicate and extend research into human magnetoreception. Given the known presence of highly-evolved geomagnetic navigation systems in species across the animal kingdom, it is perhaps not surprising that we might retain at least some functioning neural components especially given the nomadic hunter/gatherer lifestyle of our not-too-distant ancestors. The full extent of this inheritance remains to be discovered.
Open access paper: http://www.eneuro.org/content/
Magnetoreception, the perception of the geomagnetic field, is a sensory modality well-established across all major groups of vertebrates and some invertebrates, but its presence in humans has been tested rarely, yielding inconclusive results. We report here a strong, specific human brain response to ecologically-relevant rotations of Earth-strength magnetic fields. Following geomagnetic stimulation, a drop in amplitude of EEG alpha oscillations (8-13 Hz) occurred in a repeatable manner. Termed alpha event-related desynchronization (alpha-ERD), such a response has been associated previously with sensory and cognitive processing of external stimuli including vision, auditory and somatosensory cues. Alpha-ERD in response to the geomagnetic field was triggered only by horizontal rotations when the static vertical magnetic field was directed downwards, as it is in the Northern Hemisphere; no brain responses were elicited by the same horizontal rotations when the static vertical component was directed upwards. This implicates a biological response tuned to the ecology of the local human population, rather than a generic physical effect.
Biophysical tests showed that the neural response was sensitive to static components of the magnetic field. This rules out all forms of electrical induction (including artifacts from the electrodes) which are determined solely on dynamic components of the field. The neural response was also sensitive to the polarity of the magnetic field. This rules out free-radical 'quantum compass' mechanisms like the cryptochrome hypothesis, which can detect only axial alignment.
Ferromagnetism remains a viable biophysical mechanism for sensory transduction and provides a basis to start the behavioral exploration of human magnetoreception.
Significance Statement
Conclusion
Our results indicate that at least some modern humans transduce changes in Earth-strength magnetic fields into an active neural response. We hope that this study provides a road-map for future studies aiming to replicate and extend research into human magnetoreception. Given the known presence of highly-evolved geomagnetic navigation systems in species across the animal kingdom, it is perhaps not surprising that we might retain at least some functioning neural components especially given the nomadic hunter/gatherer lifestyle of our not-too-distant ancestors. The full extent of this inheritance remains to be discovered.
Open access paper: http://www.eneuro.org/content/
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Recent Electromagnetic Radiation Safety posts
- "Cell Phones, Cell Towers & Wireless Safety" (UC Berkeley Presentation)
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Twitter: @berkeleyprc
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
Website: https://www.saferemr.com
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