  Exposures to a hypomagnetic field can affect biological processes. Recently,
it has been observed that hypomagnetic field exposure can adversely affect
adult hippocampal neurogenesis and hippocampus-dependent cognition in mice. In
the same study, the role of reactive oxygen species (ROS) in hypomagnetic field
effects has been demonstrated. However, the mechanistic reasons behind this
effect are not clear. This study proposes a radical pair mechanism based on a
flavin-superoxide radical pair to explain the modulation of ROS production and
the attenuation of adult hippocampal neurogenesis in a hypomagnetic field. The
results of our calculations favor a singlet-born radical pair over a
triplet-born radical pair. Our model predicts hypomagnetic field effects on the
triplet/singlet yield of comparable strength as the effects observed in
experimental studies on adult hippocampal neurogenesis. Our predictions are
also in qualitative agreement with experimental results on superoxide
concentration and other observed ROS effects. We also predict the effects of
applied magnetic fields and oxygen isotopic substitution on adult hippocampal
neurogenesis. Our findings strengthen the idea that nature might harness
quantum resources in the context of the brain.
