Birds do not need the latest in navigational technology when it comes to flying south for the winter; they come with their own built-in GPS system that uses the Earth’s magnetic field. But just how they detect the magnetic force is still unknown. Researchers at Baylor College of Medicine are now closer to answering that question.
In a study that appears in the current edition of Science, Drs. Le-Qing Wu, post-doctoral fellow, and J. David Dickman, professor of neuroscience, both at BCM, have shown how certain brain cells in pigeons encode the direction and intensity of the Earth’s magnetic field.
Neurons play role
"We know birds and many other animals can sense the magnetic force; behavioral studies show that birds fly along magnetic routes during seasonal changes," said Dickman, who conducted much of the research at Washington University in St. Louis. "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."
Dickman said certain areas of the brain are activated when a particular area of the inner ear, known as the lagena, is exposed to a magnetic field. Without it, several of these corresponding areas in the brain show no activity.
Dickman and Wu used electrodes in one brain area, known as the vestibular nuclei, to record activity when the bird was exposed to a changing magnetic field.
"The cells responded to the angle and intensity of the magnetic field. Some cells were more sensitive depending on what direction we aimed the magnetic field around the bird’s head," Dickman said.
More studies are needed but 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. It is believed that birds use this information to create spatial maps.
"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," Dickman said. "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."
Funding for this study came from the National Institute for Deafness and Other Communications Disorders.