Magnetic fields light up 'GPS neurons',

The question of how birds navigate using - among other signals - magnetic fields is the subject of much debate. These new “GPS neurons” seem to show how magnetic information is represented in birds’ brains. David Dickman of the Baylor College of Medicine in the US set up an experiment in which pigeons were held in place, while the magnetic field around them was varied in its strength and direction. In life, this could help the bird determine not only its heading just as a compass does, but would also reveal its approximate position. Each cell also showed a sensitivity to field strength, with the maximum sensitivity corresponding to the strength of the Earth’s natural field. And just like a compass, the neurons had opposite responses to different field “polarity” - the magnetic north and south of a field, which surprised the researchers most of all.