====== Magnetoreception ====== A number of animal species, including bacteria, arthropods, molluscs, fish, [[https://sora.unm.edu/sites/default/files/journals/auk/v109n01/p0043-p0056.pdf|birds]] and mammals are known to be able to sense magnetic fields. >__Animals use geomagnetic fields for navigational cues, yet the sensory mechanism underlying magnetic perception remains poorly understood. __One idea is that geomagnetic fields are physically transduced by magnetite crystals contained inside specialized receptor cells, but evidence for intracellular, biogenic magnetite in eukaryotes is scant.\\ \\ Source : [[https://www.pnas.org/content/119/3/e2108655119|PNAS January 18, 2022 119 (3)]] {{:oa_padlock_grn.png?16&nolink|Open Access}} For some varieties of bacteria, known as [[https://en.wikipedia.org/wiki/Magnetotactic_bacteria|Magnetotactic bacteria]], the ability is now quite well explained. But for mammals and birds, for example, there are currently no agreed explanations. >The largest issue affecting verification of an animal magnetic sense is that despite more than 40 years of work on magnetoreception there has yet to be an identification of a sensory receptor. Given that the entire receptor system could likely fit in a one-millimeter cube and have a magnetic content of less than one ppm [part per million], it is difficult to discern the parts of the brain where this information is processed."\\ \\ //See// [[https://en.wikipedia.org/wiki/Magnetoreception|Magnetoreception]] at Wikipedia//.// ==== Recent experiments on human magnetoreception ==== Although there have been a large number of controlled studies intended to determine (or refute) the existence of magnetoreception in humans, the results have not been conclusive. A 2019 study from Caltech and the University of Tokyo, however, appears to show marked differences in measurements of human brain [[content:life_sciences:human_body:eeg|alpha waves]] in varying geomagnetic fields. It's important to note that the experimental subjects were not necessarily aware of the changes. //See// [[https://www.eneuro.org/content/6/2/ENEURO.0483-18.2019|Transduction of the Geomagnetic Field as Evidenced from alpha-Band Activity in the Human Brain]]. The report paper on the research ends : >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.__ //Notes:// [1] Many organisms have been found to contain materials which are quite strongly magnetic - but in general this is thought to be co-incidental. Reference example [[https://web.gps.caltech.edu/~jkirschvink/pdfs/KirschvinkBEMS92.pdf|Magnetite in Human Tissues: A Mechanism for the Biological Effects of Weak ELF Magnetic Fields-]] //Bioelectromagnetics Supplement //1:101-113 [2] Recent research in [[content:life_sciences:life_itself:ciss_theory]] is motivating experimental research efforts to see if it may have implications for magnetoreception. ---- Also see: [[content:life_sciences:zoology:avian_navigation|Pigeon navigation]]