A new study suggests that humans can subconsciously sense Earth's magnetic field. While this capability, called magnetoreception, is well known in birds and fish, there is now evidence that our brains are also sensitive to magnetic fields. The researchers from Caltech and the University of Tokyo measured the brainwaves of 26 participants who were exposed to magnetic fields that could be manipulated. Interestingly, the brainwaves were not affected by upward-pointing fields. From Science News:
Participants in this study, who all hailed from the Northern Hemisphere, should perceive downward-pointing magnetic fields as natural, whereas upward fields would constitute an anomaly, the researchers argue. Magnetoreceptive animals are known to shut off their internal compasses when encountering weird fields, such as those caused by lightning, which might lead the animals astray. Northern-born humans may similarly take their magnetic sense "offline" when faced with strange, upward-pointing fields…
Even accounting for which magnetic changes the brain picks up, researchers still don't know what our minds might use that information for, (Caltech neurobiologist and geophysicist Joseph) Kirschvink says. Another lingering mystery is how, exactly, our brains detect Earth's magnetic field. According to the researchers, the brain wave patterns uncovered in this study may be explained by sensory cells containing a magnetic mineral called magnetite, which has been found in magnetoreceptive trout as well as in the human brain.
"Transduction of the Geomagnetic Field as Evidenced from Alpha-band Activity in the Human Brain" (eNeuro)
"Evidence for a Human Geomagnetic Sense" (Caltech)