Since I remember myself, I’m fascinated with senses: What can we sense, what will happen if I’ll concentrate – how many surrounding sounds will I hear, what is color blindness and what is synesthesia, and of course, what superpowers or super-senses animals have. Luckily, it’s an endless world where almost everything is possible: Bats and dolphins use echolocation, a.k.a. bio sonar, for spatial orientation, snakes can detect infrared, the children of a Thailand tribe, The Moken, can see well underwater thanks to a special ability to change the shape of their eye lens and make the pupil smaller, in contrast to a native automatic reflex to make the pupil bigger and receive more light underwater, which causes everything to appear blurry, and the list is endless.
For us, humans, we normally characterize five senses: sight, hearing, smell, taste, and touch. Nevertheless, the actual picture is much more complicated, and the number of available senses is not well defined. For example, we have some senses that don’t fall well under any of the previous five categories, like proprioception, the sense of self-movement and body position, thermoreception, the ability to sense temperature and equilibrioception, the perception of balance and spatial orientation – those normally are considered as additional senses.
Human anatomy is rich and complicated and up to these days, it is full of surprises. In addition to the known “five” senses, people sometimes talk about a mysterious sixth sense – the ability to feel something beyond the recognized physical senses. And as extraordinary as it may sound, we actually do have a sixth sense. It appears that we can sense more than what we are aware of. We wrote about one such sixth sense in our article, “When a Legend Becomes Reality”, where we described the sense of polarization, which was discovered less than two centuries ago. Today, we want to talk about another unbelievable, but real, sense, that was discovered just a year ago: The sense of magnetism, or magnetoreception.
Many animals are sensitive to Earth’s magnetic field: Some types of birds use the Earth’s magnetic field for navigation, and they are even able to distinguish it from local anomalies, like volcanic or igneous terranes. The Monarch butterflies use an internal magnetic compass during their migrations, which helps them to navigate during cloudy days when the sun isn’t visible. Dogs are sensitive to small variations of the Earth’s magnetic field, several species spontaneously align their body axis with respect to the Earth’s magnetic field when they, well, do their business.
Magnetoreception is common in the animal world, but its presence in humans has been normally considered as not possible. It has been tested rarely – some research on the matter was performed about 30 years ago, and all the tests didn’t provide conclusive results. Behavioral experiments could not be replicated and the previous attempts to detect human brain responses using electroencephalography (EEG – a monitoring method to record the electrical activity of the brain.) were limited as well.
Since then, there have been major advances in our understanding of animal geomagnetic sensory systems. An ever-expanding list of experiments on magnetically-sensitive organisms has taught us a lot about magnetic sensing and processing. Recently, in 2019, a group of researches published a new study, that shows, this time conclusively, that magnetoreception is possible in humans as well [1].
The approach was technical and not behavioral: 36 adult volunteers entered a Faraday cage, a chamber that is isolated from external electromagnetic fields, and their brain wave activity was recorded with an EEG. The idea was that whether we can consciously detect some magnetic field or not, if we are able to sense magnetism in any way, it can be detected in the brain’s activity. They were right: The scientists found a few strongly-responding participants, that showed significant alpha-oscillations (8–13 Hz) during artificial magnetic stimulation.
A clarification from the discussed paper: The alpha-rhythm is the dominant human brain oscillation in the resting state when a person is not processing any specific stimulus or performing any specific task. Neurons engaged in this internal rhythm produce 8- to 13-Hz alpha-waves that are measurable by EEG. Individuals vary widely in the amplitude of the resting alpha-rhythm. When an external stimulus is suddenly introduced and processed by the brain, the alpha-rhythm generally decreases in amplitude compared with a pre-stimulus baseline.
The researches were lucky: Out of 36 participants, only 4 showed a strong response, and not to any magnetic stimulation, but specifically to Earth’s-like magnetic field, showing no response to other magnetic stimulation. This implicates a biological response tuned to our ecology, to our natural surrounding and evolvement, rather than a generic physical effect. The tests were repeated multiple times, over weeks or months, and those 4 individuals repeatedly showed a strong reaction, indicating that it wasn’t a chance, but indeed occurred due to Earth’s like magnetic stimulation.
This is fantastic news, and it’s truly amazing what we are capable of doing. It’s still not clear whether we are able to consciously feel and detect the Earth’s magnetic field or not. Maybe, we just need to practice it, or maybe the system lacks a conscious component and we can’t be aware of it. We still don’t know why only certain people respond while others not, and we don’t know are we able to use it and how – all those and many other questions are still open. But now, since we already know that feeling a magnetic field is something we can do, all the options are on the table, and their research will definitely continue.
Seeing all that, something that just recently was considered impossible and now it’s a scientifically known fact, I’m starting to wonder – What other senses we have?
[1] Transduction of the Geomagnetic Field as Evidenced from alpha-Band Activity in the Human Brain Connie X. Wang, Isaac A. Hilburn, Daw-An Wu, Yuki Mizuhara, Christopher P. Cousté, Jacob N. H. Abrahams, Sam E. Bernstein, Ayumu Matani, Shinsuke Shimojo and Joseph L. Kirschvink eNeuro 18 March 2019, 6 (2) ENEURO.0483-18.2019; DOI: https://doi.org/10.1523/ENEURO.0483-18.2019.
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