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Radical triads, not pairs, may explain
effects of hypomagnetic fields on neurogenesis
Jess Ramsay and Daniel R. Kattnig∗
Living Systems Institute and Department of Physics,
University of Exeter, Stocker Road, Exeter,
Devon, EX4 4QD, United Kingdom
(Dated: June 17, 2022)
Adult hippocampal neurogenesis and hippocampus-dependent cognition in mice have been
found to be adversely affected by hypomagnetic field exposure. The effect concurred with
a reduction of reactive oxygen species in the absence of the geomagnetic field. A recent
theoretic study suggests a mechanistic interpretation of this phenomenon in the framework
of the Radical Pair Mechanism. According to this model, a flavin-superoxide radical pair,
born in the singlet spin configuration, undergoes magnetic field-dependent spin dynamics
such that the pair’s recombination is enhanced as the applied magnetic field is reduced.
This model has two ostensible weaknesses: a) the assumption of a singlet initial state is
irreconcilable with known reaction pathways generating such radical pairs, and b) the model
neglects the swift spin relaxation of free superoxide, which abolishes any magnetic sensitivity
in geomagnetic/hypomagnetic fields. We here suggest that a model based on a radical triad
and the assumption of a secondary radical scavenging reaction can, in principle, explain
the phenomenon without unnatural assumptions, thus providing a coherent explanation of
hypomagnetic field effects in biology.
I. INTRODUCTION
A multitude of biological processes have been ascribed sensitivity to weak magnetic
fields, i.e., magnetic fields comparable to the geomagnetic field (GMF; 25 − 65 µT). The
artificial absence of magnetic fields, i.e., exposure to hypomagnetic field, has likewise
been linked to biological effects in cells, animals and plants [1]. A recent study by Zhang
et al. suggests that male mice exposed to hypomagnetic fields (HMF; by means of near
∗ d.r.kattnig@exeter.ac.uk