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Bioelectromagnetism

 

 

Recent experimental results suggested that humans may also possess magnetoreception (Chae et al.,

2019; Wang et al., 2019). How accurately can humans perceive the GMF without using any tools such as

magnetic compasses? If so, what is the physiological mechanism? Recently, South Korean researchers

have demonstrated in a self-rotatory chair experiment that humans sense the GMF and turn toward

food (Chae et al., 2019) within a Faraday cage, which is a conductive enclosure that shields its contents

from EFs (Engels et al., 2014). Te results demonstrated that starved men were largely oriented toward

the ambient/modulated magnetic north or east, rather than women (Chae et al., 2019). Tis is a direc­

tion that was previously related to food, without other useful clues such as sight or sound. Te orien­

tation was reproduced under blue light but was abolished under blindfold or longer wavelength light

(>500 nm), indicating that blue light is required for magnetic orientation (Chae et al., 2019). Importantly,

the reversal of the vertical component of the GMF seemed to orient in the S magnetic direction, allowing

food-induced blood glucose levels to act as a motive for sensing the direction of the MF (Chae et al.,

2019). Te results show that male humans rely on blue light to sense the GMF, suggesting that the geo­

magnetic orientations are mediated by an inclination compass (Chae et al., 2019). Tis study suggests

that blue light-dependent human magnetoreception occurs in the eyes in a manner that appears to

involve the brain and glucose, whereas the magnetoreceptor and magnetoreception mechanism (radi­

cal pair [RP] or otherwise) remains to be established (Chae et al., 2019). Te male-specifc magnetic

orientation might have originated from prehistoric male ancestors who were dominantly responsible for

gathering or hunting for food, and the varying level of individual orientation could be a diverging trait

from the evolutionary process to date (Chae et al., 2019).

A joint research team of the California Institute of Technology (Caltech), and the University of Tokyo

provided human subjects with “artifcial MFs” that have the same strength as the GMF with changes

only in the direction and inclination of the MF (Wang et al., 2019). Te directional changes of the MF

were perceived “unconsciously” by the subjects because the brainwaves showed specifc reactions (Wang

et al., 2019). Te experiment was conducted at Caltech in Pasadena, California, USA. Te research team

made an MF exposure device that changes only in the direction and inclination of the GMF, and the

recruited participants living in the local Pasadena (34 individuals; their genders, races, and ages ranging

18–68 years are variable) (Wang et al., 2019). EEG signals were measured at 64 points on the head surface

in the electromagnetically shielded room within a Faraday cage in a dark condition while simulating

the MF with the same intensity as the GMF and changing only the direction and inclination of the MF

(Wang et al., 2019).

As a result, none of the participants answered that they noticed the change in the MF (Wang et al.,

2019). However, only when they were stimulating with MF in the same direction and inclination as

they were exposed to in Pasadena, where they usually live, the α-wave component of the EEG (8–13 Hz)

decreased, leading to the response termed as α-wave event-related desynchronization (α-ERD) (Wang

et al., 2019). Te EEG data revealed that certain MF rotations could trigger strong and reproducible brain

responses (Wang et al., 2019). One EEG pattern known from existing research, called α-ERD, typically

shows up when a person suddenly detects and processes a sensory stimulus (Peng et al., 2012). Te brains

were “concerned” with the unexpected change in the MF direction, and this triggered the α-wave reduc­

tion (Wang et al., 2019). Te researchers insisted that such α-ERD patterns in response to simple mag­

netic rotations are powerful evidence for human magnetoreception (Wang et al., 2019). Te participants’

brains only responded when the vertical component of the feld was pointing downwards at ~60° (while

horizontally rotating), as it does naturally in Pasadena (60° inclination in the Northern Hemisphere),

California (Wang et al., 2019). Tey did not respond to unnatural directions and inclinations of the MF,

such as when it pointed upwards (Wang et al., 2019). Te researchers suggest the response is tuned to

natural stimuli, refecting a biological mechanism that has been shaped by natural selection (Wang et al.,

2019). In this study, only 4 out of 34 participants showed an α-wave reduction in response to magnetic

rotations. Te research team told that it was expected that only 4 out of 34 participants possess magneto-

reception (Wang et al., 2019). Just as not everyone excels in art and mathematics, the researchers think it’s

not strange that there are individual diferences in the ability to sense MFs (Wang et al., 2019).