Elusive sensory organ: Pigeons detect magnetic fields through inner ear
Scientists around former IMP group leader David Keays show that pigeons detect magnetic fields through their inner ear. Their discovery was now published in the journal Science.
Many animals – from bats, to migratory birds and sea turtles – use the Earth’s magnetic field to navigate. Yet despite decades of research, scientists still know surprisingly little about the magnetic sense. How do animals detect magnetic fields? Which brain circuits process the information? And where in the body is this sensory system located?
One hypothesis, going back to the early 19th century, speculated that magnetic sensing might occur in the inner ear, relying on the generation of small electric currents. With time this concept was forgotten, and alternative models were proposed and dismissed – the origin of the detection and processing of magnetic fields, however, remained enigmatic.
A decade of research by the Keays lab has now paid dividends, resulting in a publication in science which provides insight into the fundamentals of magnetic sensing. “State-of-the-art microscopy allowed us to identify specialized circuits that process magnetic information. Moreover, it provided a critical clue to the location of the primary magnetic sensors.”
Vienna BioCenter PhD students Grégory Nordmann and Spencer Balay observed robust activation in a brain region called the vestibular nucleus, which is connected to the inner ear. Genetic analysis of inner ear tissue revealed cells with highly sensitive electric sensors.
"The cells we describe are ideally equipped to detect magnetic fields using electromagnetic induction – enabling pigeons to find their way home using the same physical principle which permits the wireless charging of phones." In both cases, a magnetic pulse is converted into an electrical signal. For the pigeon, this powers their natural GPS.
The researchers emphasize that it is likely not the only magnetic sensing strategy in nature. "Our data suggests that there’s a ‘dark compass’ in the inner ear, while other studies point to a light-dependent compass in the visual system," explains Keays. "In all likelihood, magnetoreception has evolved convergently in different organisms. Much remains to be discovered!"
"This work would not have been possible without the support of the IMP, and the amazing skills of its Mechanical Engineering Center", reflected David Keays.
David Keays was a fellow and then a group leader at the IMP from 2008 until 2021, when he moved to the Ludwigs-Maximilians-Universität (LMU) in Munich. This announcement is based on a press release by LMU.
Original Publication
Gregory C. Nordmann, Spencer D. Balay, Thamari N. Kapuruge, Marco Numi, Christoph Leeb, Simon Nimpf, E. Pascal Malkemper, Lukas Landler, David A. Keays:
"A global screen for magnetically induced neuronal activity in the pigeon brain." Science. DOI: 10.1126/science.aea6425