They examined the mineral content of pulverised bees and pigeon heads using specially adapted geological testing equipment. In each, they discovered about 100 million particles of magnetite. This opened the possibility that Earth's magnetic force could somehow affect the nervous system by the raw movement of these millions of tiny compasses, perhaps facilitating neural communication to signal North and South.
The idea is that, when someone isn't doing anything but resting, the brain's activity level peaks and troughs rhythmically in waves at a specific frequency rate - in this case, within what is known as the 'alpha frequency' band. Then, if they hear, see or sense something, these cycles become less regular, marking a decrease in alpha activity.
