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Humans—like other animals—may sense Earths magnetic field

first_img A study published today offers some of the best evidence yet that humans, like many other creatures, can sense Earth’s magnetic field. But it doesn’t settle other questions that have swirled around this contentious idea for decades: If we do have a subconscious magnetic sense, does it affect our behavior? And does it arise from an iron mineral found in our brains, as the authors believe?“I think this paper will make quite a splash,” says Peter Hore, a physical chemist at the University of Oxford in the United Kingdom. But, he adds, “Independent replication is crucial.”A variety of species—bacteria, snails, frogs, lobsters—seem to detect Earth’s magnetic field, and some animals, such as migratory birds, rely on it for navigation. But testing for the sense in humans has been tricky. Experiments in the 1970s that asked blindfolded participants to point in a cardinal direction after being spun around or led far from home yielded inconsistent results. By Kelly ServickMar. 18, 2019 , 1:00 PM Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe Humans—like other animals—may sense Earth’s magnetic field Biophysicist Joe Kirschvink and his team used brain recordings to search for a magnetic sixth sense in people. Click to view the privacy policy. Required fields are indicated by an asterisk (*)center_img Sign up for our daily newsletter Get more great content like this delivered right to you! Country Email Spencer Lowell Biophysicist Joe Kirschvink at the California Institute of Technology (Caltech) in Pasadena is a veteran of the search. Using electroencephalography (EEG), his team recorded brain activity from electrodes on the scalp to search for some response to changes in a highly controlled magnetic field equal in strength to Earth’s.In the experiment, each of the 34 participants sat quietly in a dark aluminum box that shielded them from electromagnetic noise such as radio waves. By changing the flow of electric current through coils lining the box, the researchers created a magnetic field that sloped steeply downward, like Earth’s own field at the midlatitudes of the Northern Hemisphere. Then they rotated the field, as would happen if a person turned their head.In an EEG study with a different design, published in 2002, other researchers failed to find any brain response to a changing field. Kirschvink says data analysis techniques used at the time were not powerful enough to detect an effect. The new study, published in eNeuro, found that the rotating field sometimes elicited a marked drop in waves of the α frequency, which are typical of a brain that is awake but at rest. Many EEG studies use α to track responses to visual information, says Mary MacLean, a neuroscientist at the University of California (UC), Santa Barbara, who was not involved in the work. A change in α, she says, “is generally a good indicator of the degree to which people are engaging in sensory processing.”The effect showed up in less than a third of participants, which could indicate that genetic factors or past experiences influence a person’s sensitivity to a magnetic field, says cognitive neuroscientist Shinsuke Shimojo, another member of the Caltech team. Mysteriously, the change registered only when the field was rotated counterclockwise.“What they show is very exciting and seems robust,” says Stuart Gilder, a geophysicist at Ludwig Maximilian University in Munich, Germany. But the results call for follow-up tests, such as measuring how different field strengths and rotation speeds affect brain activity, he adds.“I’m not surprised there’s an effect,” says Margaret Ahmad, a biologist at Sorbonne University in Paris, who notes that magnetic fields are known to affect human and other mammalian cells in a dish. “There’s something in a cell that is different in the presence of a magnetic field,” she says. “We see this effect in human embryonic kidney cells; you’re not going to convince me that an effect in brain cells is of any greater or lesser significance.”The Caltech team is still far from explaining how magnetoreception is possible, scientists say. “I’m convinced that something in the brain is responding to a magnetic field in a particular way,” Maclean says. “I just have no idea … what mechanism that really represents.”The mechanism of magnetoreception is only settled for certain bacteria, which harbor magnetite crystals that align with Earth’s magnetic field. Bird beaks and fish snouts also contain magnetite, as does the human brain. Gilder and his colleagues recently found that it is most concentrated in lower, evolutionarily ancient regions—the brain stem and cerebellum. But no one has identified the proposed sensory cells that contain magnetite.Other groups suggest a protein in the retina called cryptochrome, which senses incoming light, also responds to magnetic fields. But Kirschvink’s team contends its new results tip the scales in favor of magnetite. When they reversed their magnetic field to point upward, its rotations no longer elicited a change in brain activity. Magnetite, like a compass needle, responds to a field’s direction, whereas cryptochrome would respond identically to fields with opposite polarity.“If the results are real, I think that rules out cryptochrome as the source of these effects in humans,” Hore says, though it might play a role in other animals.But is a change in brain waves alone evidence of a “sense”? Some aren’t convinced. “If I were to … stick my head in a microwave and switch it on, I would see effects on my brain waves,” says Thorsten Ritz, a biophysicist at UC Irvine. “That doesn’t mean we have a microwave sense.”More convincing would be evidence that the brain actually processes magnetic information in a way that influences behavior, Ritz says. He is intrigued by a study from a South Korean research team, published last month in PLOS ONE, which found that, in the absence of visual or auditory cues, men who had fasted for about 20 hours could sometimes orient themselves in a direction they previously associated with food.Kirschvink’s team has experiments in progress that aim to unearth subtle consequences of a magnetic sense—for example, manipulating the magnetic field to bias a person’s best guess at a cardinal direction. “That would really supersolidly establish that humans have a full-fledged magnetosensory system,” says Caltech neuroscience graduate student Connie Wang, who is first author on the new paper. The team also wants to test whether careful training could bring magnetic sensations into consciousness.If humans really use a magnetite-based sensor, there are other concerns to explore, Kirschvink says, such as whether the magnets in aviation headsets could impair pilots’ sense of direction, and whether the strong magnetic field generated by MRI machines could somehow alter our magnetite.Three years ago, Kirschvink gave a preview of these results at a meeting of the United Kingdom’s Royal Institute of Navigation, which meets every 3 years in Egham. On 12 April, at the society’s next meeting, he’ll take the stage to defend his ideas to an audience of skeptics, with data in hand. “We’re going to have a fun session,” he says.last_img read more