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eNeuro. 2019 Apr 26;6(2). pii: ENEURO.0483-18.2019. doi: 10.1523/ENEURO.0483-18.2019. Print 2019 Mar/Apr.

Transduction of the Geomagnetic Field as Evidenced from alpha-Band Activity in the Human Brain.

Author information

1
Computation and Neural Systems, California Institute of Technology, Pasadena, CA, 91125.
2
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125.
3
Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, 91125.
4
Graduate School of Information Science and Technology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8654, Japan.
5
Department of Computer Science, Princeton University, Princeton, NJ 08544.
6
Computation and Neural Systems, California Institute of Technology, Pasadena, CA, 91125 hmre.contact@caltech.edu pmag.contact@caltech.edu.
7
Tohoku University Graduate School of Life Sciences, Sendai, Miyagi 980-8577, Japan.
8
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, 91125 hmre.contact@caltech.edu pmag.contact@caltech.edu.
9
Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan.

Abstract

Magnetoreception, the perception of the geomagnetic field, is a sensory modality well-established across all major groups of vertebrates and some invertebrates, but its presence in humans has been tested rarely, yielding inconclusive results. We report here a strong, specific human brain response to ecologically-relevant rotations of Earth-strength magnetic fields. Following geomagnetic stimulation, a drop in amplitude of electroencephalography (EEG) alpha-oscillations (8-13 Hz) occurred in a repeatable manner. Termed alpha-event-related desynchronization (alpha-ERD), such a response has been associated previously with sensory and cognitive processing of external stimuli including vision, auditory and somatosensory cues. Alpha-ERD in response to the geomagnetic field was triggered only by horizontal rotations when the static vertical magnetic field was directed downwards, as it is in the Northern Hemisphere; no brain responses were elicited by the same horizontal rotations when the static vertical component was directed upwards. This implicates a biological response tuned to the ecology of the local human population, rather than a generic physical effect. Biophysical tests showed that the neural response was sensitive to static components of the magnetic field. This rules out all forms of electrical induction (including artifacts from the electrodes) which are determined solely on dynamic components of the field. The neural response was also sensitive to the polarity of the magnetic field. This rules out free-radical "quantum compass" mechanisms like the cryptochrome hypothesis, which can detect only axial alignment. Ferromagnetism remains a viable biophysical mechanism for sensory transduction and provides a basis to start the behavioral exploration of human magnetoreception.

KEYWORDS:

EEG; alpha-ERD; biogenic magnetite; biophysics; magnetoreception; quantum compass

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