Towards the neural basis of the magnetic sense in subterranean mole-rats: Behavior and recordings

The ability to sense the Earth’s magnetic field and use it for orientation and navigation is widespread in the animal kingdom. The neuronal mechanisms of this sensory ability are, however, still poorly understood. African mole-rats are subterranean mammals that are suggested to use magnetic cues for orientation in their dark tunnels. We ask which brain regions are involved in the magnetic sense and how magnetic cues are neuronally encoded in this mammalian model. First, we looked for a robust behavioral assay to demonstrate the perception of magnetic fields. We present the results of two approaches, the novel magnetic object and maze navigation. To maximize the level of experimental control, we used closed loops between live animal tracking and a magnetic coil system to create a “virtual magnetic environment”. Next, we hypothesized that mole-rat brains contain spatial neurons but that, in contrast to epigeic rodents, inputs from the somatosensory and perhaps the magnetosensory system predominate over visual cues. We tested our hypothesis by performing single-unit recordings in the hippocampus of freely moving mole-rats exploring an environment within different magnetic conditions.