This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A pigeon turning its head might seem an unlikely electricity generator. Yet one proposed explanation for the bird's magnetic sense depends on exactly that: Turning through Earth's magnetic field would produce tiny electrical signals inside its ears.
However, a theoretical study suggests that this miniature generator cannot supply directional information fast enough to work as a compass. The problem is electrical noise produced within the proposed sensor itself. Daniel Kattnig, a physicist at the University of Exeter, tested the proposal in a study now published in the Journal of the Royal Society Interface.
His analysis challenges the mechanism while leaving one intriguing observation unexplained: Magnetic fields still activate parts of the pigeon brain connected to the inner ear. The electrical idea has a physical basis. Turning a conductive loop in a magnetic field can indeed generate a voltage, and the inner ear's semicircular canals, which normally help detect head rotation, contain a salty fluid that conducts electricity.
For a 2019 study published in Current Biology, researchers generated electrical signals in an enlarged laboratory model of a canal. They also identified molecular components associated with electrical sensing in pigeon inner ear tissue. Later research by Gregory Nordmann and colleagues, published in Science, strengthened the biological case.
Magnetic stimulation activated brain regions connected to the balance system, even when it was generated in darkness. The team also identified specialized sensory cells that express genes for voltage-sensitive channels associated with electrical sensing. For those experiments, the birds' heads were held still while the magnetic field was rotated, changing its direction relative to the inner ear without requiring the birds to turn their heads.
Together, the findings suggested a route from a changing magnetic field to electrical signals and brain activity. But beyond producing a voltage, the signal would also have to carry enough information to indicate direction. For the new study, Kattnig modeled a canal as a small ring of conductive fluid interrupted by a gelatinous barrier called the cupula.
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