Blue light-dependent human magnetoreception in geomagnetic food orientation
(A) A schematic drawing of a subject sitting on the rotatable chair and the direction of geomagnetic north during the food association/no association phase and the actual test. Left: Frontal view of the subject. Subjects had to wear earmuffs and close their eyes for the duration of the experiment. Middle and right: Top view of the subject facing toward the ambient geomagnetic north during the food association/no association phase, and four modulated geomagnetic norths, one of which was randomly provided to the subject during the test. Note that geomagnetic east instead of geomagnetic north was tested in a set of experiments in Fig 2. The subjects could choose to rotate clockwise or counterclockwise as indicated by the arrows during the test. mN, magnetic north; square, the vertical Helmholtz coils; circle, the subject; black closed triangle, the facing direction of the subject; red open triangle(s), the direction of ambient geomagnetic north (middle) or modulated geomagnetic north (right). (B) The procedure and timeline for the geomagnetic food orientation assay. Food was provided for ‘association’ trials only. (C) The light and magnetic field conditions for the experiments. The subjects had their eyes closed to avoid distraction and to prevent visual cues from aiding in the locating of the modulated magnetic north. Subjects were provided with either a full wavelength of light or light filtered by either a blindfold or filter glasses. Intensity, light intensity on the surface of the eyelids; Yes and No, inversion of the vertical component of the magnetic field was performed or not performed; Figure, the figure(s) in which the indicated experimental condition was provided.