Good question. The general consensus seems to be that it enables a primitive form of magnetoreception,
Kirschvink thinks magnetite is the key. Receptor cells containing crystals of magnetite could register changes in magnetic fields and report this information to the brain. This is almost identical to what magnetotactic bacteria do. They have structures containing nanoscale magnetite crystals called magnetosomes. These essentially act as biological compasses, allowing the bacteria to navigate.
https://www.realclearscience.com/blog/2019/06/11/why_is_there_magnetite_in_the_human_brain.html
Apparently research has shown that humans may have some small degree of magnetoreception.
Magnetite is widely distributed in the brain but especially concentrated in the brainstem and cerebellum. It also seems to be produced by the brain’s own chemistry, so it might play an important role doing something.
Another alternative that occurs to me is that magnetite plays some role in neurons that increases sensitivity to the brain’s own EM field.
Broad Speculations 
When I read your title I was guessing that they finally figured out why I have such a magnetic personality. Very disappointed. Plus I have no sense of direction so can’t even compete with pigeons.
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I saw something on PBS that explained pigeon homing with the smell sense. Maybe you should try that sense. 🙂
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Similar to Steve, my sense of direction is pretty poor. I also have a history of iron deficiency. I would assume iron brings in the magnetite. Hmmm. 🤔
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Interesting. So what’s being proposed here is that the brain uses our planet’s magnetic field as sense input for various yet to be determined bodily functions, and in an entirely non-conscious capacity. I like how they simply measured differences in brain alpha wave production for subjects that either were or were not exposed to the earth’s magnetic field. Better yet would be to test some actual body functions to see if any would be so altered. But if the human body does use the earth’s magnetic field somehow, I guess this could at least be a start.
I suppose it can be strange to think of senses in a non-conscious capacity, though actually I’d say that all conscious senses exist non-consciously first. Eye based light information might be used algorithmically by the brain in many ways. Theoretically however the brain also goes beyond this to provide phenomenal vision information for an actual experiencer to use.
In an interview I recall McFadden talking about how the eyes of certain birds might create a compass through quantum mechanics. A quick google search suggests that this has been a fertile ground of study for others as well. https://www.google.com/amp/s/www.sciencenews.org/article/quantum-mechanics-compass-songbird-physics/amp
Here the theorized magnetic sensor for birds is a protein called cryptochrome 4 rather than magnetite however.
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I don’t think the magnetite is related to magnetoreception of the earth’s magnetic field.
I think it serves some other function. I think this might provide a clue.
“Scientists have mapped magnetic materials in human brains for the first time, revealing that our brains may selectively contain more magnetic material in their lower and more ancient regions.
Researchers used seven specimens donated in Germany to measure brain tissue for signs of magnetite, Earth’s most magnetic mineral. Scientists have known that other types of life, such as special kinds of bacteria, contain magnetite. But the distribution of magnetite in human brains has been unclear because no systematic study had mapped the mineral in human tissue before”
Also, this:
“Gilder applied the same two-step technique to the brain samples. The comparison revealed that the human brain had a detectable magnetism after a magnetic field had been applied to the samples. The results showed that magnetite was in “almost every piece” of the specimens, said Gilder”.
https://eos.org/articles/human-brains-have-tiny-bits-of-magnetic-material
The more ancient the part of the brain, the greater the concentration, but it’s all over the brain. So some possibilities suggest to me.
1- The magnetite directly enhances neurons or firings.
2- It enhances EM feedback.
3- It provides a carry-over EM effect from one synchronous firing to the next which may help account for continuity.
4- It is a component of a system of EM field sensors which create the actual feeling of consciousness.
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I guess I have no reason to think that my body uses such a sense. And if it did then why wouldn’t evolution have passed it over to the conscious side as well? Surely a human with an inherent conscious sense of north would tend to do better than otherwise.
As a proponent of the idea that consciousness exists as the proper kind of EM field, all of your speculation seems reasonable to me. Or perhaps the magnetite exists for some other reason. Surely it’s not there by accident. I’d think that McFadden would be exploring this if he thought it might add to his theory. And perhaps he is.
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I don’t see much evidence that humans use the earth geomagnetic field for navigation. That studies have discovered an influence on brainwaves from small electromagnetic fields, such as those of earth, does indicate sensitivity to weak EM fields by neurons.
There was a paper out suggesting magnetite is in the brain as a pollutant. But there isn’t any evidence of the concentration increasing with age nor is it concentrated solely around the olfactory system, which the theory would expect. It is all over and especially in the brainstem which might be expected if it has something to do with normal brain operation. It would be interesting to know if similar findings extend to other animals. I don’t know that is the case and I can’t seem to find that anyone has investigated it. Even if the magnetite is only in humans or primates, it still might be an enhancement on neural function but not absolutely required for consciousness.
If it is associated with consciousness and widely found in animals, its presence in the brainstem might suggest a long evolutionary history for consciousness. It might also suggest either neurons or some specialized subset of neurons in the brain act similarly to sensory neurons but, instead of detecting something external to the organism, they are detecting the brain’s own operation, The “something it is like” would have its basis in the brain feeling its own internal neural activity.
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