Magnetobiology & Magnetoreception [Resources]

New 2018 paper by Binhi & Prato "Nonspecific biological effects of weak magnetic fields depend on molecular rotations"

Abstract
The radical pair mechanism is a leading hypothesis in animal magnetic navigation. This mechanism associates the magnetic sense with the visual system, the radical pairs in cryptochromes of the eye retina being specialized magnetic receptors that modulate rhodopsin-mediated photoreception. There are also nonspecific magnetic effects in biology, which occur mostly by chance and originate from the interaction of weak magnetic fields with the magnetic moments dispersed all over the organism at the microscopic level. The radical pair mechanism cannot explain this type of response for many reasons. We have previously shown that the above interaction has a finite probability of resulting in an observable. Here, we develop our physical model of nonspecific magnetic effects for the case of magnetic moments located in rotating molecules. We generalize the results of recent experiments on gene expression in plants in a constant magnetic field, and show that the precession of the magnetic moments that reside on rotating molecules can be slowed relative to the immediate biophysical structures. In quantum mechanical language, the crossing of the quantum levels of magnetic moments conjointly with molecular rotations explain nonspecific magnetic effects and leads to magnetic field-dependences that are in good agreement with the experiment.

https://www.researchgate.net/publication..._rotations

A new study on Magnetoreception in birds - Bojarinova et al (2020) - which complicates the issue.

The team developed a minaturised magnetic field coil that generated a tiny hyper-weak magnetic field that did not extend very far, and stuck it to the head of the Robins. First they tested the Robins disorientation using the large field coils generating the same oscillation pattern at 5nT magnetic field strength, this confirmed the robins were disoriented in the presence of the field. Then they tested them with the miniaturised field coil mounted directly to their heads using the same oscillation pattern and a magnetic field strength of 2-3nT, unfortunately the robins were not disorientated at all, and flew in the same direction as control Robins.

This causes a problem, as it suggests the mechanism used for hyper-weak magnetic field sensing is more complicated... indeed it begins to look like there is perhaps further processing involved. Considering Landler et al (2015) paper - mentioned earlier in this thread - which also suggested a much more complicated mechanism at work, that seemed to involve the encoding of spatial location, suggesting a role for magnetic fields involved in encoding memory, it's possible Bojarinova et al (2020) are seeing a different perspective of the same issue.

I've made a quick diagram, showing one possible option to consider, which is the curvature of the fields from the large coils, vs the miniature coil intersecting the Robins head is very different. Considering Landler et al (2015) very fine field effect again, it almost looks like the field with tighter curvature is somehow being recognized/disregarded by the mechanism which is behind the magnetoreception phenomena in Robins.




Magnetic compass of garden warblers is not affected by oscillating magnetic fields applied to their eyes

Abstract: The magnetic compass is an important element of the avian navigation system, which allows
migratory birds to solve complex tasks of moving between distant breeding and wintering locations.
The photo-chemical magnetoreception in the eye is believed to be the primary biophysical mechanism
behind the magnetic sense of birds. It was shown previously that birds were disoriented in presence of
weak oscillating magnetic fields (OMF) with frequencies in the megahertz range. The OMF effect was
considered to be a fingerprint of the photo-chemical magnetoreception in the eye. In this work, we used
miniaturized portable magnetic coils attached to the bird’s head to specifically target the compass
receptor. We performed behavioral experiments on orientation of long-distance migrants, garden
warblers (Sylvia borin), in round arenas. The OMF with the amplitude of about 5 nT was applied locally
to the birds’ eyes. Surprisingly, the birds were not disoriented and showed the seasonally appropriate
migratory direction. On the contrary, the same birds placed in a homogeneous 5 nT OMF generated by
large stationary coils showed clear disorientation.

https://www.researchgate.net/publication...their_eyes

Very exciting paper from May 2019... which I missed... This study robustly proves strong neural processes in the brain are being recruited by environmental magnetic fields... the race is on... all the other mainstream candidate mechanisms have fallen away, except Magnetite. The paper is free... if you read nothing else, read the general discussion... Very very exciting...

Our results indicate that at least some modern humans transduce changes in Earth-strength magnetic fields into an active neural response. We hope that this study provides a road-map for future studies aiming to replicate and extend research into human magnetoreception. Given the known presence of highly-evolved geomagnetic navigation systems in species across the animal kingdom, it is perhaps not surprising that we might retain at least some functioning neural components especially given the nomadic hunter/gatherer lifestyle of our not-too-distant ancestors. The full extent of this inheritance remains to be discovered.

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

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.

https://europepmc.org/backend/ptpmcrende...obtype=pdf

Conference study paper... suggesting Human non-conscious detection of geomagnetic strength magnetic fields, which also show a relationship to encoding memory (spatial)

Blue light-dependent human magnetoreception in geomagnetic food orientation

Kwon-Seok Chae*1, I-T. Oh, S-H. Lee, S-Ch. Kim
1 Kyungpook National University

Magnetic fields, including the Earth’s geomagnetic field (GMF), are known to influence a wide phylogenetic range of creatures with magnetoreception, from bacteria to mammals, as a sensory cue or a physiological modulator. Despite some previous evidence, it is largely accepted that humans cannot sense magnetic fields. Here, we show that humans sense the GMF to orient their direction toward food in a self-rotatory chair experiment.

Starved men significantly oriented toward the 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, 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, indicating that orientation is dependent on an inclination compass. Moreover, blood glucose levels resulting from food appeared to act as a motivator for sensing a magnetic field direction.

The results demonstrated that humans can sense the GMF and use it for magnetic food orientation when starved, and suggest that a cryptochrome-mediated radical pair mechanism may underlie the magnetoreceptive behaviors.

https://journals.plos.org/plosone/articl...ne.0211826