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Clinical Trial
, 14 (2), e0211826
eCollection

Blue Light-Dependent Human Magnetoreception in Geomagnetic Food Orientation

Affiliations
Clinical Trial

Blue Light-Dependent Human Magnetoreception in Geomagnetic Food Orientation

Kwon-Seok Chae et al. PLoS One.

Erratum in

Abstract

The Earth's geomagnetic field (GMF) is known to influence magnetoreceptive creatures, from bacteria to mammals as a sensory cue or a physiological modulator, despite it is largely thought that humans cannot sense the GMF. Here, we show that humans sense the GMF to orient their direction toward food in a self-rotatory chair experiment. Starved men, but not women, significantly oriented toward the ambient/modulated magnetic north or east, directions which had been previously food-associated, without any other helpful cues, including sight and sound. The orientation was reproduced under blue light but was abolished under a blindfold or a longer wavelength light (> 500 nm), indicating that blue light is necessary for magnetic orientation. Importantly, inversion of the vertical component of the GMF resulted in orientation toward the magnetic south and blood glucose levels resulting from food appeared to act as a motivator for sensing a magnetic field direction. The results demonstrate that male humans sense GMF in a blue light-dependent manner and suggest that the geomagnetic orientations are mediated by an inclination compass.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Schematic drawing of the geomagnetic food orientation assay.
(A) A schematic drawing of a subject sitting on the rotatable chair and the direction of geomagnetic north during the food association/no association phase and the actual test. Left: Frontal view of the subject. Subjects had to wear earmuffs and close their eyes for the duration of the experiment. Middle and right: Top view of the subject facing toward the ambient geomagnetic north during the food association/no association phase, and four modulated geomagnetic norths, one of which was randomly provided to the subject during the test. Note that geomagnetic east instead of geomagnetic north was tested in a set of experiments in Fig 2. The subjects could choose to rotate clockwise or counterclockwise as indicated by the arrows during the test. mN, magnetic north; square, the vertical Helmholtz coils; circle, the subject; black closed triangle, the facing direction of the subject; red open triangle(s), the direction of ambient geomagnetic north (middle) or modulated geomagnetic north (right). (B) The procedure and timeline for the geomagnetic food orientation assay. Food was provided for ‘association’ trials only. (C) The light and magnetic field conditions for the experiments. The subjects had their eyes closed to avoid distraction and to prevent visual cues from aiding in the locating of the modulated magnetic north. Subjects were provided with either a full wavelength of light or light filtered by either a blindfold or filter glasses. Intensity, light intensity on the surface of the eyelids; Yes and No, inversion of the vertical component of the magnetic field was performed or not performed; Figure, the figure(s) in which the indicated experimental condition was provided.
Fig 2
Fig 2. Geomagnetic field-sensitive food orientation in starved men.
(A) and (B) The subjects had meals normally and were tested under the no association experimental condition. There was no notable magnetic north orientation in the unstarved men (A) and women (B). (A) α = 64.4°, r = 0.06, P = 0.43 (V test), P = 0.93 (Rayleigh test), n = 20. (B) α = 207.1°, r = 0.06, P = 0.64 (V test), P = 0.92 (Rayleigh test), n = 21. (C) and (E) No magnetic north orientation in the starved men (C) and women (E), when they were tested under the no association experimental condition. (C) α = 79.7°, r = 0.12, P = 0.45 (V test), P = 0.77 (Rayleigh test), n = 20. (E) α = 152.3°, r = 0.31, P = 0.96 (V test), P = 0.14 (Rayleigh test), n = 21. (D) and (F) A significant (D) and unremarkable (F) magnetic north orientation in the starved men and women, respectively, tested after the food association. (D) α = 350.0°, r = 0.51, P = 0.00043 (V test; 95% confidence interval, 326.9°–31.1°), P = 0.004 (Rayleigh test), n = 20. (F) α = 206.8°, r = 0.28, P = 0.96 (V test), P = 0.19 (Rayleigh test), n = 21. (G) and (H) An unremarkable (G) and a significant (H) magnetic east orientation in the starved men under the no association and the food association condition, respectively. (G) α = 285.8°, r = 0.24, P = 0.92 (V test), P = 0.33 (Rayleigh test), n = 20. (H) α = 83.2°, r = 0.34, P = 0.015 (V test; 95% confidence interval, 33.2°–133.2°), P = 0.09 (Rayleigh test), n = 20. Circular statistical analyses were performed using the V test and Rayleigh test for all experiments. Note that throughout the study, the V test was more appropriate to evaluate whether the subjects oriented toward the magnetic north (east) along which the food association/no association phase was conducted. In each circular diagram, each of the dots and arrow indicate the subject’s mean direction vector and group mean vector of the subjects, respectively. Throughout, the dashed circle, solid outer circle, and solid inner circle indicate the gradation of 0.25, the maximum value (i.e., 1.0) for the length of a subject’s mean vector, and the minimum length of the group mean vector needed for significance in the Rayleigh test (P = 0.05), respectively. mN, the modulated magnetic north; mE, the modulated magnetic east; α, group mean vector as clockwise degree; r, length of group mean vector. The dashed lines and the solid arc indicate the confidence interval and the minimum length of the group mean vector needed for significance in the V test (P = 0.05), respectively.
Fig 3
Fig 3. Reception of blue light by the eye is necessary for geomagnetic food orientation in starved men.
The starved men were tested after the food association under different light conditions or a particular magnetic field condition. (A) and (C) An unremarkable magnetic north orientation under the blindfold (A) and the light (500–800 nm) (C). (A) α = 292.5°, r = 0.13, P = 0.52 (V test), P = 0.79 (Rayleigh test), n = 20. (C) α = 64.7°, r = 0.06, P = 0.44 (V test), P = 0.94 (Rayleigh test), n = 20. (B) A significant magnetic north orientation under the light 400–800 nm. α = 349.7°, r = 0.44, P = 0.003 (V test; 95% confidence interval, 311.4°–28.0°), P = 0.02 (Rayleigh test), n = 20. (D) A significant magnetic orientation toward magnetic south under inversion of the vertical component of the GMF (− Z) with the light (350–800 nm). α = 178.4°, r = 0.50, P = 0.00062 (V test; 95% confidence interval, 145.2°–211.6°), P = 0.006 (Rayleigh test), n = 20. The dashed lines and the solid arc indicate the confidence interval and the minimum length of the group mean vector needed for significance in the V test (P = 0.05), respectively. mN, the modulated magnetic north; α, group mean vector as clockwise degree; r, length of group mean vector.
Fig 4
Fig 4. Glucose-motivated magnetic orientation in starved men.
(A) Orientation profiles of unstarved men (top), starved men (middle), and (starved men–unstarved men) (bottom) from the tests in Fig 2A, 2C and 2D and Fig A in S2 Fig. The orientation index was calculated as [absolute value of (direction vector angle– 180°)] ∕ 180 and ranges 0 to 1. In each trial, the dot and error bar indicate the mean and standard error of the mean (SEM) of the 20 male subjects, respectively. (B) An analysis of the data in (A). (left, center) In each session, the values of mean and error bar denote the mean and SEM of dots in the corresponding session of a), respectively. (right) Mean and error bar of a session indicate the mean and SEM of the values calculated as [(orientation index value of a trial in the center)–(orientation index value of the same trial in the left)] in the session. Analysis of variance (ANOVA) test, n.s.: not significant. *, P < 0.05; **, P < 0.01. (C) Blood glucose levels during the magnetic north orientation assay in men (left) and women (right). In a separate set of experiments, blood glucose level at shortly before the first session and immediately after each session was determined in the same starved or unstarved men and women subjects. Student’s t-test, n.s.: not significant. #, P < 0.01; **, P < 0.0001; ***, P < 0.000001. Statistical values are presented as mean ± standard error of the mean (SEM).

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References

    1. Blakemore R. Magnetotactic bacteria. Science 1975; 190: 377–379. - PubMed
    1. Maffei ME. Magnetic field effects on plant growth, development, and evolution. Front Plant Sci 2014; 5: 445 10.3389/fpls.2014.00445 - DOI - PMC - PubMed
    1. Johnsen S, Lohmann KJ. The physics and neurobiology of magnetoreception. Nat Rev Neurosci 2005; 6: 703–712. 10.1038/nrn1745 - DOI - PubMed
    1. Wiltschko W, Wiltschko R. Magnetoreception. Bioessays 2006; 28: 157–168. 10.1002/bies.20363 - DOI - PubMed
    1. Merlin C, Heinze S, Reppert SM. Unraveling navigational strategies in migratory insects. Curr Opin Neurobiol 2012; 22: 353–361. 10.1016/j.conb.2011.11.009 - DOI - PMC - PubMed

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Grant support

This research was supported by 2018R1A2B2007227 grant to KSC through the National Research Foundation of Korea (NRF, http://www.nrf.re.kr/eng/main) funded by the Korea government (MSIT). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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