For some creatures, the magnetic field that hugs our planet serves as a compass for navigation or orientation.
Migratory birds, sea turtles and certain types of bacteria are counted among the species with this built-in navigation system. But what about humans? According to a new study, humans can also sense Earth’s magnetic field.
The new study, published today (March 18) in the journal eNeuro, provides the first direct evidence, from brain scans, that humans can do so, likely through magnetic particles scattered around the brain.
The ability to detect the magnetic field, called magnetoreception, was first suggested to exist in humans back in the 1980s. But subsequent studies of the brain, from the 1990s, didn’t find evidence of the ability.
But with access to new data analysis techniques, an international group of researchers decided to take another look.
To study whether humans can sense the magnetic field, 34 adults were asked to sit in a dark test chamber adorned with large, square coils. Electric currents traveled through these coils, changing the magnetic field in the chamber..
The intensity of this magnetic field was about the same as the one that surrounds our planet, said lead study author Connie Wang, a doctoral student at the California Institute of Technology. For comparison, it’s about 100,000 times weaker than the ones created by MRI machines, Wang noted.
The participants were told to relax and close their eyes while the researchers manipulated the magnetic field around them. During the experiment, electroencephalogram (EEG) machines measured a type of brainwave called an alpha wave. Alpha waves are known to decrease in amplitude when the brain picks up a signal, whether it be sight, sound … or something magnetic.
Of the 34 participants, brain scans from four individuals showed strong reactions to one change in the magnetic field: a shift from northeast to northwest. This shift would be the same as a person outside the chamber shifting their head quickly from left to right, except the head moves through the static magnetic field rather than the field moving around it.
In the four individuals, alpha brain waves decreased in amplitude by as much as 60 percent. But they responded only when the field shifted from northeast to northwest — not in the other direction.