Neuroscientists have finally established just how birds use the built-in 'GPS' system that helps them navigate using the Earth’s magnetic field.
Researchers at Baylor College of Medicine say they've discovered how certain brain cells encode the direction and intensity of the Earth’s magnetic field.
"We know birds and many other animals can sense the magnetic force; behavioral studies show that birds fly along magnetic routes during seasonal changes," says professor J David Dickman.
"It is still unknown what exactly acts as a receptor within the bird; however, in our current study we are able to show how neurons in the pigeon’s brain encode magnetic field direction and intensity. This is how we believe birds know their position on the surface of the Earth."
Certain areas of the brain are activated when an area of the inner ear known as the lagena is exposed to a magnetic field. The scientists used electrodes in an area known as the vestibular nuclei to record activity when a pigeon was exposed to a changing magnetic field.
The cells responded to the angle and intensity of the magnetic field. The sensitivity of some depended on the angle of the magnetic field around the bird’s head, showing that they were 'tuned' to specific directions.
Dickman believes the vestibular neurons are part of the receptor network that detects and sends information about the direction and intensity of the Earth's magnetic field to the rest of the brain.
"Birds give us a unique opportunity to study how the brain develops these spatial maps and the receptors that feed into it because they have such a great ability to navigate," he says.
"Birds actually have more similarities to the human brain than not, so understanding these characteristics could eventually lend itself to understanding how we create spatial maps and those disorders that affect these areas of the brain."
The sudy doesn't show exactly how the birds sense the magnetic field in the first place, although it indicates that some sort of as yet-undiscovered magnetoreceptive cell could be responsible.