Unruled Notebook

There is a pet in-house theory in this part of the world that one should not sleep by keeping one’s head in the north side. The “scientific reason” given for this (by one of the elders in my house) is that if you sleep with your head resting in north direction, the earth’s magnetic field will adversely affect the body and hence your health. At least, sleeping north-south is supposed to induce lots of nightmares. I have been prompted time and again to lay my bed east west.

I am skeptical of this pet-theory as I am yet to find conclusive evidence that humans are affected by magnetic fields, that too, as weak as that produced by our geo-magnetic field. The only testable proposition of the above pet-theory is subjective and concerns my health. The only tangible verification is nightmares, which I don’t get, irrespective of the direction I sleep. I do get dreams, but they happen irrespective of my sleep direction. The in-house explanation for this of course is that if I never sleep north-south, my health would have been even better than what it is now.

One can never win such arguments you know.

Anyway, just to seek an answer to my doubt let me conjecture this. If my nightmares are controlled by my sleep position, which in turn is supposed to be influenced by the geomagnetic field, then one could conjecture that somehow the geomagnetic field affects human brain activity. At first glance, this seems possible. After all, the neurons in the brain, when active, are electrical signals (charges) in motion. It is possible that such a moving charge is influenced by a magnetic field of spatially or temporally varying field strength.

So I explored for corroboration for this phenomenon. For instance, the recent Physics Today article [see reference 1 below] that I mentioned in an earlier Cat crossing post, states that human tissue is found to be not influenced by magnetic fields. It says, this is one reason intuitive understanding or the medical literature on human senses doesn’t help much in detecting the mechanism for magneto-reception in humans and animals.

[...] humans do not appear to have the ability to sense magnetic fields. Whereas most nonhuman senses, such as polarization detection and UV vision, are relatively straightforward extensions of human abilities, magnetoreception is not.

Also, the geomagnetic field is very weak for easy detection as stated in the above article

[...] the weakness of the interaction between Earth’s field and the magnetic moments of electrons and atoms, roughly one five-millionth of the thermal energy kT at body temperature, makes it difficult to even suggest a feasible mechanism.

A further web search landed me with at least three different evidences that suggest human magnetic sense [follow the links in reference 2 below]. But let me discuss here the results from a recent peer reviewed research paper in Neuroscience journal [see reference 3 below].

The paper title “Evidence of a nonlinear human magnetic sense” itself intrigues us. The authors have done experiments with 17 humans subjected to a local magnetic field (2 Gauss, 60 Hz – a field strength comparable to that in the general environment) applied around their head. See the picture below for the schematic of the experiment, taken and reorganized from the paper. Schematic (a) shows the magnetic field application, while (b) shows the measurement of brain electrical activity.

By measuring the brain activity through electrodes kept at various location on the head (see (b) in picture above), the authors are able to show that magnetosensory evoked potentials (MEPs) in the brain or its activity in terms of electrical signals is altered (or affected) by the switch on and switch off of such a 2 G magnetic field. To quote from the lucidly written discussion section of the paper (even a non-expert like me can follow it easily)

[...] the observed changes in brain electrical activity were true MEPs. The results therefore can be interpreted to show that human subjects possess a magnetic sense. The mechanism of this sense as well as the anatomic location at which it is mediated (see below) remains unelucidated. Further, transduction of the field (conversion into an electrical signal by a receptor) did not result in perception, as in the case of the special senses. Thus the “magnetic sense” must be understood more narrowly, similar to the chemical senses for detection of pH, O₂, and blood pressure.

To put this finding in perspective, I quote one more paragraph from the discussion section in full (omitting the references)

Strong magnetic fields (10,000 G), such as those used for transcutaneous magnetic stimulation, instantaneously activate voltage-sensitive ion channels in axonal membranes. Fields on the order of 1 G cannot do so, and their biophysical mechanism of action is still unknown. Nevertheless, they can produce electrophysiological changes in animals throughout the phylogenetic spectrum. In some species, specialized receptor organs have been described. The anatomical basis for the detection of weak fields by human beings, however, has not been located. Consequently, the best evidence presently possible that human beings possess a magnetic sense consists of measurements of potentials evoked by a field stimulus. The primary objective of this study was to provide direct evidence indicating that detection of weak fields was a form of sensory transduction.

Bold font-face is mine.

So let me speculate now – I am no expert in neuroscience – to answer my doubt about my sleep position.

Even if human brain activity could be influenced by a magnetic field, while sleeping, neuron activity of the brain is expected to be minimal – not a conducive situation for magnetoreceptive interaction leading to nightmares. Further, as the current scientific knowledge indicates, there is no conclusive proof that humans exhibit magneto-reception anywhere in their body (leave alone brain) to detect the weak geomagnetic field (weaker than what is tested in the experiment discussed above). Brain activity is evidenced only to be influenced by proximity external magnetic stimulus. So I don’t need to relate my nightmares – if I get them – to my sleep position.

My dreams and nightmares could after all have a simple explanation in what I ate that day. Wonder how what I eat can affect my dreams? Well that is another age old belief in this part of the world that needs exploration.

References

1. Sönke Johnsen and Kenneth J. Lohmann, Magnetoreception in animals, March 2008, page 29, Physics Today

2. Magnetoreception Wikipedia page [sites one two three webpages that discuss human and animal magnetic sense]

3. CARRUBBA, S., FRILOTII, C., CHESSONJR, A., MARINO, A. (2007). Evidence of a nonlinear human magnetic sense. Neuroscience, 144(1), 356-367. DOI: 10.1016/j.neuroscience.2006.08.068