Some animals can sense the Earth’s magnetic field and use it for navigation, scientists have long wondered whether humans also have this kind of magnetoreception. Exposing human subjects to an Earth strength magnetic field pointed in different directions in laboratory settings lead researchers from Japan and the USA to discover distinct brain wave patterns that occur in response to rotating the field in a certain way; offering evidence of people subconsciously responding to the Earth’s magnetic field.
“Previous studies of human magnetoreception have yielded inconclusive results, this new evidence is a step forward, and it is hoped replications can be seen and further investigations in the future,” says Can Xie biophysicist at Peking University.
26 subjects wore an EEG cap to record the electrical activity of their brain while sitting with their eyes closed in a quiet dark chamber lined with electrical coils that manipulated the magnetic field inside the chamber so that it was the same strength as Earth’s natural field, and could be pointed in any direction. This simulated effects of turning in different directions in Earth’s natural unchanging field without the participants moving, the complete stillness prevented motor control thoughts from tainting brain waves due to the magnet field.
EEG readouts were compared to controls in which the magnetic field inside the chamber did not move; alpha waves were analysed to determine whether the brain reacted to changes in magnetic field direction which typically dominate EEG readings while a subject is sitting idle but fade when a sensory input is received.
Changes in the magnetic field were observed to trigger changes in subject alpha waves, specifically when the magnetic field pointed toward the floor in front of the subject facing north which is the direction Earth’s magnetic field points in the Northern Hemisphere. Changing the field counterclockwise from northeast to northwest was observed to triggered an average 25% dip in amplitude of alpha waves, which was about 3 times as strong as natural alpha wave fluctuations seen in the control trials. Subjects showed no responses to rotating the magnetic field toward the ceiling in the direction of Earth’s field in the Southern Hemisphere; 4 subjects were rested weeks to months later and showed the same responses.
If the yielded results can be replicated it raises several questions such as why do subjects appear to respond to downward but not upward pointing fields. “All of the subjects came from the Northern Hemisphere and should perceive the downward field as natural, upwards could constitute an anomaly. Animals are known to shut off their internal compass when they encounter weird fields, it is possible the Northern born subjects may be doing similar. Although the explanation seems plausible it will need to be tested in a study with participants from the Southern Hemisphere,” explains Joseph Kirschvink.
Even when taken into account which magnetic changes the brain may pick up, it is still not known what the brain uses the information for, or how the brain detects the Earth’s magnetic field. Uncovered brain wave patterns may be explained by sensory cells containing magnetite minerals, future studies will either confirm or eliminate this possibility.
“This is the first evidence of humans subconsciously processing magnetic signals, now researchers can try to identify brain regions this originates from and try to identify the nature of the cells responsible,” explains Michael Winklhofer of the University of Oldenburg.
