Magnetic Field Polarity Fails to Influence the Directional Signal Carried by the Head Direction Cell Network and the Behavior of Rats in a Task Requiring Magnetic Field Orientation

Many different species of animals including mole rats, pigeons, and sea turtles are thought to use the magnetic field of the earth for navigational guidance. While laboratory rats are commonly used for navigational research, and brain networks have been described in these animals that presumably mediate accurate spatial navigation, little has been done to determine the role of the geomagnetic field in these brain networks and in the navigational behavior of these animals. In Experiment 1, anterior thalamic head direction (HD) cells were recorded in female Long-Evans rats while they foraged in an environment subjected to an experimentally generated magnetic field of earth-strength intensity, the polarity of which could be shifted from one session to another. Despite previous work that has shown that the preferred direction of HD cells can be controlled by the position of familiar landmarks in a recording environment, the directional signal of HD cells was not influenced by the polarity of the magnetic field in the enclosure. Because this finding could be attributed to the animal being insensitive or inattentive to the magnetic field, in Experiment 2, rats were trained in a choice maze task dependent on the ability of the animals to sense the polarity of the experimentally controlled magnetic field. Over the course of 28 days of training, performance failed to improve to a level above chance, providing evidence that the spatial behavior of laboratory rats (and the associated HD network) is insensitive to the polarity of the geomagnetic field.