Credit: CC0 Public Domain
The human brain can unconsciously respond to changes in Earth's magnetic fields, according to a team of geoscientists and neurobiologists.
Reported in eNeuro, this interdisciplinary study revives a research area in neuroscience that has remained dormant for decades.
Many animals, such as migratory birds and sea turtles, have a geomagnetic sense that supports their biological navigation system. Although magnetoreception has been well-studied in these animals, scientists have not yet been able to determine whether humans share this ability.
Geoscientist Joseph Kirschvink, neuroscientist Shin Shimojo, and their colleagues at Caltech and the University of Tokyo set out to address this long-standing question using electroencephalography to record adult participants' brain activity during magnetic field manipulations. Carefully controlled experiments revealed a decrease in alpha-band brain activity—an established response to sensory input—in some participants. The researchers replicated this effect in participants who responded strongly and confirmed these responses were tuned to the magnetic field of the Northern Hemisphere, where the study was conducted.
Future studies of magnetoreception in diverse human populations may provide new clues into the evolution and individual variation of this ancient sensory system.
Is electrical induction responsible for the brainwave response? (Ans: no). The six diagrams show the strength of the alpha-waves (~ 10 Hz) in the human brain, at 64 locations on the human head for different magnetic field rotations; note the symbols for the nose and ears for reference. The bottom row of diagrams shows experiments with the North-seeking direction of the field pointing stably downwards at an inclination of 60? (as in the Northern Hemisphere), and the top row with the field pointing upwards. The left pair of diagrams show results from the counter-clockwise rotation of the horizontal component of the geomagnetic field (CCW from NE to NW), the middle column is the opposite rotation (CW from NW to NE), and the right shows one of the control conditions where the field did not rotate, but data are analyzed in the same fashion. Data are shown at about half a second after the field shifts (or not, for the FIXED control). Only the downwards CCW stimulation causes a significant drop in the alpha-wave band (shown by the deep blue in the lower left diagram). Note that electrical induction will depend only upon the moving, horizontal component of the magnetic field, not the static vertical component. The lack of response in the upwards CCW stimulation (top right diagram) contradicts predictions of the electrical induction hypothesis. This shows that the effect is not an artifact of any form of electrical induction, including from the electrodes on the scalp. Credit: Wang et al., eNeuro (2019)
More information: Transduction of the Geomagnetic Field as Evidenced from Alpha-band Activity in the Human Brain, eNeuro, DOI: 10.1523/ENEURO.0483-18.2019
Provided by Society for Neuroscience
