Jorge Conesa

The Language and Cognition Laboratory

1 Reprint requests should be sent to J. Conesa Ph.D., Social Sciences Department, Everett Community College, Everett, WA 98201. (jconesa@ctc.ctc.edu). I would like to thank Chad Lewis for invaluable input prior to submission to Science. Also, I am thankful to Cynthia Brunold-Conesa for proofreading earlier versions of this manuscript.

RUNNING HEAD: HEMISPHERIC ACTIVATION AND GEOMAGNETIC ORIENTATION

Abstract

Evidence of a purported human geomagnetic orienting ability has been controversial even though the initial Baker reports argued convincingly for such an ability. This ability has now been tested and shown on several animal species. Aware of the limitations of earlier experimental procedures, we devised simpler methodology. For example, we recorded cerebral hemispheric activation while subjects where involved in a stationary and unobtrusive orienting-to-North task. By doing this we found that right-hemisphere activation coincided with greater accuracy at ‘guessing’ magnetic North. We also found that geomagnetic orienting accuracy was greater during experimental conditions where subjects were facing a North-South axis as opposed to an East-West axis.

Hemispheric Activation and Geomagnetic Orientation/ Jorge Conesa

Aware of earlier approaches we made some fundamental methodological changes while testing whether humans are able to use geomagnetic cues for orientation. First, we thought that the bus displacement and spinning (blindfolding subjects) chair experiments may have added a confound, namely, activating vestibular sense systems (2). To us, it seemed less cumbersome to test the ability for orienting to magnetic north while on a stationary position, eyes open and by simply drawing a dot or arrow on a 360 degree paper polar plot. Behaviorally, orienting in this way mimics mammalian-terrestrial pause-and-hesitation behavior while obtaining a bearing. In our procedure, subjects were allowed to rotate their heads while ‘guessing’ where north was. Accuracy of obtaining this bearing was smaller deviation from magnetic north in degrees. Furthermore, our first and second experimental series suggested that accuracy in this task was associated with head positioning along two main directional axes: north-south and east-west. So in the present study we included a statistical comparison of accuracy for ‘guessing’ north between these two vectors. We tested each cardinal position twice in four different classrooms at three separate building locations on a Pacific Northwest campus. Our task involved asking subjects to guess where north was, as quickly as possible (within 8 sec.).

Familiarity with the layout of the experimental rooms was diminished by closing curtains or blinds in each of these sites. Also, most subjects were from the freshman class therefore unfamiliar with the layout of the testing rooms. Most subjects exhibited an obvious discomfort and frustration at not being able to look outside the curtained windows in order to orient themselves. In order to eliminate nuisance variables we preferred adhering to the more stringent experimental protocols which included subjects being naive to the exact direction of geomagnetic North and to their hemispheric activation at the time of the trial.

Additionally, a few seconds prior to this task, we assessed cerebral hemispheric activation while subjects where involved in the orienting-to-north task. Earlier human magnetic navigation reports, with the hopes of finding evidence of a magnetoreceptor, did not include a consideration of the role of the right hemisphere in spatial relations processing and the role of the right-hemisphere in transient and vigilance behavior (7). If a magnetic sense exists in humans, the role of the right-hemisphere should be considered in order to obtain a more complete and cognitive, as well as a magnetosensorial, view of human geomagnetic navigation. The reason for this is because of the right hemisphere’s amply reported spatial processing functions.

In order to assess hemispheric activation we employed a neurophysiologically sensitive technique, the Nostril Dominance Test (NDT). The NDT is used as a functional index for the Human Nasal Cycle. The Human Nasal Cycle is a periodic shift in nostril dominance which follows an average ultradian periodicity of about 90 minutes throughout the 24-hour period. Furthermore, research has provided evidence that EEG recordings of the cerebral hemispheres correlate with shifts in nostril dominance. More specifically, they found (5) that increased synchronization of alpha, beta, delta and theta brain waves occurred in the hemisphere contralateral to the dominant or less congested nostril. Also, previous laterality research has confirmed the validity of this technique whenever assessment of hemispheric activation is required during orientation tasks (4).

Typically, assessment of nostril dominance/hemispheric activation in a randomly chosen group of subjects yields a 50/50 ratio. That is, half the subjects would exhibit one dominance or the other; our null hypothesis. Therefore, any changes of this typical ratio occurring under experimental conditions would be due to something other than a chance event within statistically appropriate confidence parameters. The first hypothesis makes the theoretical assumption that accuracy to ‘guessing’ magnetic north will be associated with significant deviations of this 50/50 ratio favoring right-hemisphere activation.

A two-way analysis of variance, using sex and hemispheric condition, showed a significant effect of hemispheric activation [ F (1, 79)= 6.70, p < .01]. Thus, accuracy for ‘guessing’ North was greater for those subjects who exhibited left-nostril/right-hemisphere dominance/activation. Earlier reports found a significant main effect of sex with males being more accurate than females during the right-hemisphere condition. This effect was not replicated and disappeared when we pooled all the data (F > .05).

Using the responses of our right-hemisphere active subjects only, we found a significant difference between direction vectors, north-south and east-west [Fisher PLSD, 23.27, p<.05]. Namely, accuracy for ‘guessing’ north was greater when subjects aligned their heads on a north-south orientation rather than an east-west vector. The average deviation at each geomagnetic position as well as the combined accuracy for the north-south and east-west axes was as follows:

In view of the decade-long controversy about whether humans are able to orient by using geomagnetic cues, the present experimental series confirms the findings (1) that humans are sensitive to geomagnetic cues. This series indicate that this sensitivity is present whenever subjects are facing a north-south axis. These findings stand on their own merit even if one discounts the NDT as a direct measure of hemispheric activation. Furthermore the present report offers simpler experimental protocols and statistical analyses that can be easily replicated by researchers. Second, this series focuses on right-hemisphere processes as a possible organizing cerebral region responsible for utilizing geomagnetic directional data. We are hesitant at this point to speculate on possible human magnetoreceptor-right/hemisphere neuronal interfaces since a discovery and full description of the purported organelle remains a goal.

Admittedly, the role of the right-hemisphere in magnetic orientation must be explored with respect to the more sensorial mechanisms described above. In the end, one can not rule out that our right-hemisphere findings may be driven by more cognitive processes whereas our second, axonal findings may reflect sensorial mechanisms yet to be described.

REFERENCES

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35 691-704 (1987).

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Newman, S. Beua, C. Sanders K., Thurman, J. Moore, J. Heinz, A. Van Dyke, E. Pedack

Poster presented at the Western Psychological AssociationÕs 77th Annual Convention ,

Seattle, Washington (April 24, 1997); J. Conesa Perceptual and Motor Skills 80 1263-1273

(1995); J. Conesa Perceptual and Motor Skills 85 579-584 (1997.)

5. M. Hasegawa and E. Kern, E. Mayo Clinic Proceedings 52 28-34 (1977); J. Keuning

International Rhinology 6 99-136 (1968); D. A.Werntz, R. G. Bickford, F. E. Bloom, D. S.

Shannahoff-Khalsa Human Neurobiology 2 39-43 (1983).

6. I am grateful to Drs. Robin Baker, Doreen Kimura and Chad Lewis for suggestions which

improved a previous version of this manuscript. I am also grateful to Brunold-Conesa and

expert referees for reviewing a previous version of the present manuscript. Special thanks to

Penny Potter, Seo Chika, Katie Gilyeat and Jill Brown. Reprints requests should be sent to

Dr. Jorge Conesa, The Language and Cognition Laboratory, Psychology Dept., EvCC, 801

Wetmore Ave., Everett, WA 98201 (jconesa@ctc.ctc.edu).

7. Note: Experimental areas were checked for sources* of magnetic anomalies (ferrous objects

and hidden sources of generators or conductors) which might have: i) raised the ambient

geomagnetic filed, or ii) created local field distortions. These areas were clear of such

interference. * Vernier Magnetic field sensor (Hall Effect transducer) range +/- 3.2 x 10-4

tesla and +/- 6.4 x 10-3 tesla. This sensor was connected to a Macintosh PowerBook 145B

with Vernier Serial Box Interface. The magnetic data was analyzed using Vernier Data

Logger software.