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Human Rotational Magnetoreception

June 2010 Paulsen

Changes in conscious state after a 2 minute immersion in a slowly rotating replica of the Earth's magnetic field have been demonstrated in human subjects. A series of double-blind tests were conducted at 9 fixed rotation rates from 0.1 rev/sec to 20 rev/sec (revolutions per second), and continuous sweeps from 0.08 to 0.6 rev/sec. Effects ranged from mild spaciness to strong "high" sensations, and varying degrees of reading impairment. Onset was typically delayed about 5 minutes. Peak effect strength occurred at about 25 minutes, fading to normalcy after about 1.5 hours.


Three orthogonal 2 meter diameter Helmholtz coils simultaneously null the Earth's field and generate a new field that can be rotated at arbitrary rates. The apparatus allows testing a subject's response to turning in the Earth's magnetic field while the subject remains stationary. This method avoids stimulating the vestibular, visual, and proprioceptive senses, thus allowing the magnetic effects to be studied in isolation.

Background

The ability to orient and navigate by sensing the Earth's magnetic field is widespread in the animal kingdom. Numerous behavioral studies have demonstrated magnetic sensing in insects[1], crustaceans[2], molluscs[3], fish[4], amphibians[5], birds[6], and mammals[7].

Humans were shown to have magnetic orienting abilities by Baker[8] in 1980, in a study that moved blindfolded subjects over long distances near Manchester, England. But efforts by Gould & Able[9] in 1981 to replicate Baker's results in the United States failed. A later series of experiments conducted in the U.K. by Westby & Partridge[10] also failed to replicate Baker's findings. In 2002 Sastre et al.[11] looked for changes in EEG and subjective reports in 50 subjects after exposure to static alterations of the Earth's magnetic field. None were found. More recently, a 2009 study by Souman et al.[12] that used GPS to track subjects for several hours, showed that when lost, humans deprived of visual cues will walk in random circles.

In contrast to the few investigations looking for human responses to the Earth's static magnetic field, a vast number of studies have searched for health effects caused by man-made extremely low frequency (ELF) fields, mostly at power line frequencies of 50-60 Hz. (For an extensive 400+ page review of the literature, see the 2007 WHO publication Extremely Low Frequency Fields.[13]) Despite decades of investigations, ELF magnetic fields have not been found to affect the health of humans, nor have humans been shown capable of detecting such fields when they were no stronger the Earth's static field. However, a few studies have detected changes in the EEG at field strengths similar to the Earth's static field.[14]

Experiments published on this website demonstrate that there are humans capable of sensing angular motion with respect to the Earth's magnetic field. Also, a simple protocol has been developed that gives a robust and reproducible response in those subjects. This should facilitate many additional experiments, and encourage replication by other workers.

Equipment and Procedures

The apparatus used 6 individual copper coils arranged in pairs to form 3 orthogonal Helmholtz[15] coils, and was oriented so that the 3 axes of the Helmholtz coils were aligned with the Earth's magnetic north-south (N-S) and east-west (E-W), and vertical. Direct currents fed to the N-S and vertical coils cancelled the Earth's static magnetic field within a 1 meter diameter region in the center of the device. Quadrature sinusoidal currents supplied to the E-W and N-S coils produced a uniform 25 microTesla magnetic field that rotated about a vertical axis. The quadrature signals were AM encoded on a 2 kHz sinewave carrier, and recorded onto music CDs. The CDs were then played back from an ordinary portable CD player. The stereo signals from the CD player were decoded with analog AM demodulators and sent to high current DC amplifiers. The currents fed to the Helmholtz coils were calibrated by measuring voltage drops across precision 0.1 ohm resistors in series with all 3 coils. See equipment details...

To conduct blind tests, the quadrature signals were recorded on individual un-marked CDs. Before the tests, the CDs were shuffled and marked with a series of identifying numbers, which were recorded along with the test results in a written notebook. At the end of the series the contents of the CDs were identified. Thus, a person could conduct an entire series of tests with no knowledge of what was on the individual CDs. See procedure details...

Results

As of June 2010, two series of blind tests have been conducted using myself as the test subject. In addition, a large number of non-blinded trials have been conducted on myself and one other subject, many of which were recorded in detail.


Fig. 1. Average recorded strength ratings for the first 30 minutes of each blinded, fixed frequency trial. Magnetic exposure time in each trial was 2 minutes, except for the zero-speed trial which had no magnetic field.

Fig. 1. shows the results of 10 blind trials conducted at similar times on separate days. Changes in conscious state were self-reported, and were necessarily subjective, noisy, and prone to the placebo effect. The "weak" level in this series should be considered the noise floor. What appears to be an anomaly at 0.2 Hz (rev/sec) may disappear with further tests (a repeat test at 0.2 Hz gave a medium effect). The weak effect at 20 Hz was expected, from previous work using permanent magnet devices (see below).


Fig. 2. Scatter plot of 63 numerical strength assessments (green dots) recorded during 10 fixed-frequency blinded trials. Only 55 points are visible; 6 are identical to 6 others, and 2 are off-scale to the right. Yellow curve is a 3rd-order polynomial fit to the red 10-point moving average, which was phase corrected 5 points to the left. Enlarge

Fig. 2. combines the 10 trials from Fig. 1  into a single plot by making use of all 63 numerical values that were recorded during each trial (1-weak, 2-medium, 3-strong). To make the plot, the data points from each trial were combined and sorted by time in ascending order. A polynomial fit could not be directly applied to the data, so a 10 point moving average was used to reduce it to a more tractable form. The peak of the curve agrees with a simple average (26 minutes) of the times to reach maximum effect in each trial .


Fig 3.         Yellow line = sweeps         Green line = controls
Scatter plot of 87 numerical strength assessments (small dots) recorded during 10 swept-frequency blinded trials. Line plots are phase-corrected 10-point moving averages. Enlarge

Fig. 3. shows the results of 2-minute frequency sweeps from 0.08 to 0.6 Hz. Ten blinded trials were conducted; 5 were controls with no signal, and 5 were sweeps. Of the 10 trials, there was one false positive and one false negative. The false negative cannot be explained by any known equipment problems, however the test protocol provided erroneous hints that the trial in question was a control. The false positive might have been caused by spurious signals from the AM demodulator, or by current transients when the DC offsets were switched on and off. The problems with the test protocol, AM demodulator, and DC offset switching have been corrected in preparation for a new series of experiments.

Several non-blind 0.08 to 0.6 Hz sweep tests gave similar results to the blind tests, as did another non-blind test of a 0.1-1 Hz sweep.

In addition to subjective self-reporting of effect strengths over time, numerous written comments, including subjective estimations of reading impairment, were recorded. Blood pressure and pulse rate were measured before and after many of the trials. Also, a 15 minute cognitive computer test was taken after 4 of the fixed frequency sessions. See details of test results...

The present studies build on my experiments with rotating permanent magnet devices over the past decade. These devices have been tried on 20 subjects, including many hundreds of sessions on myself and one other subject. Of the 20 subjects tested, 11 had a very strong response, reporting feeling spaced-out, stoned, or drugged. Nine subjects had no response at all, even after repeated exposures on different days. See details of permanent magnet devices...

Conclusions

The magnetic field strength used in these experiments is similar to the horizontal component of the Earth's natural magnetic field,[16] and the rotation rates below 1 Hz are within the range of normal turning movements made by humans.[17] This suggests that the sensory mechanism elucidated by the Helmholtz apparatus must also be stimulated when humans turn about in the natural environment. The biological function of the purported mechanism remains unknown.


Footnotes and References

  1. Kirschvink, J.L., Padmanabha, S., Boyce, C.K., and Oglesby, J., (1997). "Measurement of the threshold sensitivity of honeybees to weak, extremely low frequency magnetic fields." Journal of Experimental Biology Vol. 200, 1363-1368.
     
  2. Lohmann, K.J., Pentcheff, N.D., Nevitt, G.A., Stetten, G.D., Zimmer-Faust, R.K., Jarrard, H.E., Boles, L.C., (1995). "Magnetic Orientation of Spiny Lobsters in the Ocean: Experiments with Undersea Coil Systems." Journal of Experimental Biology Vol. 198, 2041–2048.
     
  3. Willows, A. O. D., (1999). "Shoreward orientation involving geomagnetic cues in the nudibranch mollusk Tritonia diomedea." Marine and Freshwater Behaviour and Physiology Vol. 32, 181-192.
     
  4. Molteno, T.C.A., Kennedy, W.L., (2009), "Navigation by Induction-Based Magnetoreception in Elasmobranch Fishes." Journal of Biophysics Vol. 2009, Article ID 380976, 6 pages.
     
  5. Deutschlander, M.E., Phillips, J.B., Borland, S.C., Ross, S.T., (2000), "Magnetic Compass Orientation in the Eastern Red-Spotted Newt, Notophthalmus viridescens: Rapid Acquisition of the Shoreward Axis." Copeia Vol. 2000, Issue 2, 413-419.
     
  6. Cadiou, H., McNaughton, P.A., (2010), "Avian magnetite-based magnetoreception: a physiologist's perspective." Journal of the Royal Society Interface, published online before print.
     
  7. Pavel, N., Altmann, J., Marhold, S., Burda, H., Oelschläger, H.A., (2001), "Neuroanatomy of Magnetoreception: The Superior Colliculus Involved in Magnetic Orientation in a Mammal." Science Vol. 294, 366-368.
     
  8. Baker, R. R., (1980), "Goal orientation of blindfolded humans after long-distance displacement: possible involvement of a magnetic sense." Science Vol. 210, 555-557.
     
  9. Gould, J. L., Able, K. P., (1981). "Human homing: an elusive phenomenon." Science Vol. 212, 1061-1063.
     
  10. Westby, G.W. & Partridge, K.J., (1986), "Human homing: still no evidence despite geomagnetic controls." Journal of Experimental Biology, Vol. 120, 325-331.
     
  11. Sastre A., Graham C., Cook M.R., Gerkovich M.M., and Gailey P., (2002) "Human EEG responses to controlled alterations of the Earth''s magnetic field." Clinical Neurophysiology, Vol. 113, 1382-1390.
     
  12. Souman, J.L., (2009), "Walking Straight into Circles." Current Biology, Vol. 19, 1538-1542.
     
  13. van Deventer, E., Ohkubo, C., Saunders, R., van Rongen, E., Kheifets, L., Portier, C., (2007), "Extremely Low Frequency Fields, Environmental Health Criteria Monograph No.238." World Health Organisation, International EMF Projects, published online. The monograph is available on the WHO website.
     
  14. Cvetkovic, D., Cosic, I., (2009) "Alterations of human electroencephalographic activity caused by multiple extremely low frequency magnetic field exposures." Med Biol Eng Computing Vol. 47, 1063–1073.
     
  15. A Helmholtz coil consists of 2 identical coils spaced apart by 1/2 coil radius. It produces a very uniform magnetic field within a large central volume. See Wikipedia article for more information.
     
  16. The 25 microTesla field strength used in these experiments is equal to the typical horizontal magnetic field strength over most of the Earth's surface. Charts of the Earth's magnetic field are available on the web from the U.S. Geological Survey.
     
  17. A simple test with a stopwatch demonstrated that I could turn continuously around on my feet at more than 0.6 rev/sec for 5 turns.