Humans can detect changes in the Earth’s magnetic field

Many animals can sense variations in the Earth’s magnetic field and use this sense to orient themselves. But a recent study shows that humans may also have this ability.

We have evolved to detect a range of sensory inputs, including light, sound, and smell. Other members of the animal kingdom have developed sensitivities that seem to go beyond our capabilities. Many species, including some bacteria, birds, mollusks, and marine mammals, exhibit magnetoreception. That is, they can detect fluctuations in magnetic fields.

They use this ability to orient themselves in the environment and to navigate. In the 1980s, a lot of research was done to find out if humans could detect these subtle variations, but the results were contradictory and difficult to replicate.

The debate died down. Recently, however, scientists at the California Institute of Technology in Pasadena and the University of Tokyo in Japan decided that the time had come to re-examine magnetoreception in humans.

Detecting the Earth’s Magnetic Field: A New Approach

In the 40 years since the first wave of interest in human magnetoreception, scientists have drawn a much more detailed picture of how this sense works in animals. Scientists have learned that some animals use a dual approach to navigating using magnetic fields: a compass and a map. The compass response simply uses the field to orient the animal relative to the local north/south direction. The magnetic card is more detailed. It uses the strength and direction of the field to build a picture of where the animal is in relation to where it wants to go.

It seems obvious that while we can detect magnetic fields, we are not aware of them. The authors of the recent study believe this is the main reason for the failure of previous studies. They were looking for behavioral responses to something humans probably sense unconsciously. Over the past few decades, brain scan technology has advanced by leaps and bounds.

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It is now possible to measure brain activity with much more precision than before. So, rather than looking for behavioral responses, the scientists decided to directly measure responses in the brain. They published their fascinating findings in the journal eNeuro.

Observe alpha rhythms

The researchers used EEG scanning technology to study brain activity. At the same time, they manipulated the magnetic field inside an isolated chamber protected against radio frequencies. They paid particular attention to the alpha rhythm of the participants.

They explain why:
The alpha rhythm is the dominant oscillation of the resting human brain. When a person does not process any specific stimulus or perform any specific task. When an external stimulus is suddenly introduced and processed by the brain, the alpha rhythm generally decreases in amplitude.

Scientists call this measurable change in activity “event-related alpha desynchronization.” As they expected, they found that in some participants there was a decrease in alpha event-related desynchronization as the magnetic field changed. However, the magnitude of the response varied considerably between participants.

Sensitivity to changes in the earth’s magnetic field

In the second set of experiments, the researchers focused on participants with the most robust responses to magnetic field changes. By examining these people, they were able to confirm that their answers were tuned to the magnetic field of the northern hemisphere, where the study took place.

The authors conclude that the results indicate that the human brain does indeed selectively collect and process directional inputs from magnetic field receptors. This question has been a hot topic in the scientific community for decades. It will therefore take more than one study to definitively prove that humans can detect changes in the Earth’s magnetic field.

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However, if scientists manage to prove that humans can detect magnetic fields, will that be such a shock? Given the known presence of highly evolved geomagnetic navigational systems in species across the animal kingdom, it is perhaps unsurprising that we can retain at least some functional neural components. Especially given the nomadic hunter/gatherer lifestyle of our not-so-distant ancestors. The full extent of this legacy remains to be discovered.



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