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(Phys.org)—A scientist who has dedicated a significant portion of his life to proving or disproving the notion that humans have an ability to detect and respond to Earth's magnetic field has given a talk at this year's meeting of the Royal Institute of Navigation at the University of London, suggesting that he has found evidence that it is true. Joe Kirschvink with the California Institute for Technology reported that experiments he and colleagues have been conducting have shown reproducible changes in brainwaves of volunteers who sat in a magnetically controllable chamber. Read more at: phys.org...
Birds do it. Bees do it. But the human subject, standing here in a hoodie—can he do it? Joe Kirschvink is determined to find out. For decades, he has shown how critters across the animal kingdom navigate using magnetoreception, or a sense of Earth’s magnetic field. Now, the geophysicist at the California Institute of Technology (Caltech) in Pasadena is testing humans to see if they too have this subconscious sixth sense. Kirschvink is pretty sure they do. But he has to prove it. He takes out his iPhone and waves it over Keisuke Matsuda, a neuroengineering graduate student from the University of Tokyo. On this day in October, he is Kirschvink’s guinea pig. A magnetometer app on the phone would detect magnetic dust on Matsuda—or any hidden magnets that might foil the experiment. “I want to make sure we don’t have a cheater,” Kirschvink jokes.
Every few years, the Royal Institute of Navigation (RIN) in the United Kingdom holds a conference that draws just about every researcher in the field of animal navigation. Conferences from years past have dwelt on navigation by the sun, moon, or stars—or by sound and smell. But at this year’s meeting, in April at Royal Holloway, University of London, magnetoreception dominated the agenda. Evidence was presented for magnetoreception in cockroaches and poison frogs. Peter Hore, a physical chemist at the University of Oxford in the United Kingdom, presented work showing how the quantum behavior of the cryptochrome system could make it more precise than laboratory experiments had suggested. Can Xie, a biophysicist from Peking University, pressed his controversial claim that, in the retina of fruit flies, he had found a complex of magnetic iron structures, surrounded by cryptochrome proteins, that was the long-sought magnetoreceptor. Then, in the last talk of the first day, Kirschvink took the podium to deliver his potentially groundbreaking news. It was a small sample—just two dozen human subjects—but his basement apparatus had yielded a consistent, repeatable effect. When the magnetic field was rotated counterclockwise—the equivalent of the subject looking to the right—there was sharp drop in α waves. The suppression of α waves, in the EEG world, is associated with brain processing: A set of neurons were firing in response to the magnetic field, the only changing variable. The neural response was delayed by a few hundred milliseconds, and Kirschvink says the lag suggests an active brain response. A magnetic field can induce electric currents in the brain that could mimic an EEG signal—but they would show up immediately. Kirschvink also found a signal when the applied field yawed into the floor, as if the subject had looked up. He does not understand why the α wave signal occurred with up-down and counterclockwise changes, but not the opposite, although he takes it as a sign of the polarity of the human magnetic compass. “My talk went *really* well,” he wrote jubilantly in an email afterwards. “Nailed it. Humans have functioning magnetoreceptors.” Others at the talk had a guarded response: amazing, if true. “It’s the kind of thing that’s hard to evaluate from a 12-minute talk,” Lohmann says. “The devil’s always in the details.” Hore says: “Joe’s a very smart man and a very careful experimenter. He wouldn’t have talked about this at the RIN if he wasn’t pretty convinced he was right. And you can’t say that about every scientist in this area.” Two months later, in June, Kirschvink is in Japan, crunching data and hammering out experimental differences with Matani’s group. “Alice in Wonderland, down the rabbit hole, that’s what it feels like,” he says. Matani is using a similarly shielded setup, except his cage and coils are smaller—just big enough to encompass the heads of subjects, who must lie on their backs. Yet this team, too, is starting to see repeatable EEG effects. “It’s absolutely reproducible, even in Tokyo,” Kirschvink says. “The doors are opening.”
Birds do it. Bees do it.
Thermoception: Ability to sense heat and cold. This also is thought of as more than one sense. This is not just because of the two hot/cold receptors, but also because there is a completely different type of thermoceptor, in terms of the mechanism for detection, in the brain. These thermoceptors in the brain are used for monitoring internal body temperature.
The mounting scientific evidence for magnetoreception has largely been behavioral, based on patterns of movement, for example, or on tests showing that disrupting or changing magnetic fields can alter animals’ habits. Scientists know that animals can sense the fields, but they do not know how at the cellular and neural level. “The frontier is in the biology—how the brain actually uses this information,” says David Dickman, a neurobiologist at the Baylor College of Medicine in Houston, Texas, who in a 2012 Science paper showed that specific neurons in the inner ears of pigeons are somehow involved, firing in response to the direction, polarity, and intensity of magnetic fields. Finding the magnetoreceptors responsible for triggering these neurons has been like looking for a magnetic needle in a haystack. There’s no obvious sense organ to dissect; magnetic fields sweep invisibly through the entire body, all the time. “The receptors could be in your left toe,” Kirschvink says.
originally posted by: Thecakeisalie
a reply to: skywatcher44
Cool find, but I have doubts.
The Arctic tern can fly from pole to pole without knowing the route on their first attempt, but we humans need directions or familial routes to get from point A to point B. To extrapolate, imagine a child in LA learning to ride a bike for the first time and then rode to Manhattan without looking at a map.
The magnetic compass of migratory birds has been suggested to be light-dependent. Retinal cryptochrome-expressing neurons and a forebrain region, “Cluster N”, show high neuronal activity when night-migratory songbirds perform magnetic compass orientation. By combining neuronal tracing with behavioral experiments leading to sensory-driven gene expression of the neuronal activity marker ZENK during magnetic compass orientation, we demonstrate a functional neuronal connection between the retinal neurons and Cluster N via the visual thalamus.
Humans are not believed to have a magnetic sense, even though many animals use the Earth's magnetic field for orientation and navigation. One model of magnetosensing in animals proposes that geomagnetic fields are perceived by light-sensitive chemical reactions involving the flavoprotein cryptochrome (CRY). Here we show using a transgenic approach that human CRY2, which is heavily expressed in the retina, can function as a magnetosensor in the magnetoreception system of Drosophila and that it does so in a light-dependent manner. The results show that human CRY2 has the molecular capability to function as a light-sensitive magnetosensor and reopen an area of sensory biology that is ready for further exploration in humans.